Merge remote-tracking branch 'upstream/master'

.travis.yml

-language: bash
+language: go
+go:
+  - "1.12"
 sudo: required
 services:
   - docker
 env:
+  - TEST=shellcheck
   - TEST=heroku-18 STACK=heroku-18
   - TEST=heroku-16 STACK=heroku-16
   - TEST=cedar-14 STACK=cedar-14
   - TEST=hatchet
   - TEST=unit
+  - TEST=test-binary GO111MODULE=on
 install:
   - if [[ -n $STACK ]]; then
       docker pull "heroku/${STACK/-/:}";

CHANGELOG.md

@@ -2,6 +2,64 @@
 
 ## master
 
+## v148 (2019-05-02)
+- Dark-launch new semver matching logic for node binaries (#663)
+
+## v147 (2019-05-01)
+- Dark-launch new semver matching logic for yarn binaries (#661)
+- Add node 12.x as a supported version for Node Metrics beta (#662)
+
+## v146 (2019-04-25)
+- Deprecate io.js as an alternative runtime (#658)
+- Prototyping new version resolution approach to replace Nodebin (#649 - #657)
+
+## v145 (2019-04-16)
+- Separate prebuild step in log output (#646)
+- Clean up script metrics and logging (#647)
+
+## v144 (2019-04-08)
+- Remove temporary wraning about "run build" change (#644)
+
+## v143 (2019-03-28)
+- Internal logging changes (#637, #631, #630)
+
+## v142 (2019-03-11)
+- Add temporary warning about "run build" when the build fails as well (#639)
+
+## v141 (2019-03-11)
+- Add temporary warning about "run build" change to log output (#636)
+
+## v140 (2019-03-11)
+- Run the build script by default (#628)
+
+## v139 (2019-03-04)
+- Make breaking change warning header brighter (#627)
+
+## v138 (2019-02-20)
+- Add new Build header (#625)
+- Fix yarn run error when script is empty string (#624)
+
+## v137 (2019-02-14)
+- Internal logging changes (#620, #618, #621)
+- Detect build scripts even when they are empty (#617)
+
+## v136 (2019-02-09)
+- Add warning for the upcoming run build change (#616)
+
+## v135 (2019-02-06)
+
+- Fix bug where failing builds on CI would not fail CI (#613)
+- Internal logging changes (#596, #600)
+
+## v134 (2018-12-20)
+
+- Internal changes (#593, #591)
+- Handle `$MEMORY_AVAILABLE` when `memory.limit_in_bytes` is nonsensically large (#531)
+
+## v133 (2018-11-28)
+
+- Add warning for flatmap-stream 404 failure (#590)
+
 ## v132 (2018-11-12)
 
 - Quietly add new build script behavior behind a flag (#584, #585)
@@ -66,6 +124,7 @@
 ## v119 (2018-02-28)
 
 - Install and prune devDependencies by default (#519)
+- [Breaking] Stop setting the env var `NPM_CONFIG_PRODUCTION=true` by default
 
 ## v118 (2018-02-02)
 

README.md

@@ -86,3 +86,8 @@ make test-heroku-16
 The tests are run via the vendored
 [shunit2](https://github.com/kward/shunit2)
 test framework.
+
+## Updating go binaries
+
+If you would like to develop and update the go binaries you will need to install 
+[go 1.12](https://golang.org/doc/install#install) and [upx](https://upx.github.io/)

bin/detect

@@ -17,7 +17,7 @@ error() {
 	exit 1
 }
 
-if [ -f $1/package.json ]; then
+if [ -f "$1/package.json" ]; then
   echo 'Node.js'
   exit 0
 fi
@@ -59,7 +59,7 @@ If you are trying to deploy a Node.js application, ensure that this
 file is present at the top level directory. This directory has the
 following files:
 
-$(ls -1p $1)
+$(ls -1p "$1")
     
 If you are trying to deploy an application written in another
 language, you need to change the list of buildpacks set on your

bin/test-compile

 #!/usr/bin/env bash
+# bin/test-compile <build-dir> <cache-dir> <env-dir>
 
-BP_DIR=$(cd "$(dirname ${0:-})"; cd ..; pwd)
+### Configure environment
 
-source $BP_DIR/lib/environment.sh
+set -o errexit    # always exit on error
+set -o pipefail   # don't ignore exit codes when piping output
+
+### Configure directories
+
+BP_DIR=$(cd "$(dirname "${0:-}")" || exit; cd ..; pwd)
+
+### Load dependencies
+# shellcheck source=lib/environment.sh
+source "$BP_DIR/lib/environment.sh"
+
+### Set up test Node environment
 
 export NPM_CONFIG_PRODUCTION=${NPM_CONFIG_PRODUCTION:-false}
 export NODE_ENV=${NODE_ENV:-test}
-"$BP_DIR/bin/compile" "$1" "$2" "$3"
 
+### Compile the app
+
+"$BP_DIR/bin/compile" "$1" "$2" "$3"
 write_ci_profile "$BP_DIR" "$1"

ci-profile/nodejs.sh

+#!/usr/bin/env bash
+
 export PATH="$HOME/.heroku/node/bin:$HOME/.heroku/yarn/bin:$PATH:$HOME/bin:$HOME/node_modules/.bin"
 export NODE_HOME="$HOME/.heroku/node"
 export NODE_ENV=${NODE_ENV:-test}

cmd/resolve-version/main.go

+package main
+
+import (
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"os"
+	"regexp"
+	"runtime"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/Masterminds/semver"
+)
+
+type result struct {
+	Name                  string     `xml:"Name"`
+	KeyCount              int        `xml:"KeyCount"`
+	MaxKeys               int        `xml:"MaxKeys"`
+	IsTruncated           bool       `xml:"IsTruncated"`
+	ContinuationToken     string     `xml:"ContinuationToken"`
+	NextContinuationToken string     `xml:"NextContinuationToken"`
+	Prefix                string     `xml:"Prefix"`
+	Contents              []s3Object `xml:"Contents"`
+}
+
+type s3Object struct {
+	Key          string    `xml:"Key"`
+	LastModified time.Time `xml:"LastModified"`
+	ETag         string    `xml:"ETag"`
+	Size         int       `xml:"Size"`
+	StorageClass string    `xml:"StorageClass"`
+}
+
+type release struct {
+	binary   string
+	stage    string
+	platform string
+	url      string
+	version  *semver.Version
+}
+
+type matchResult struct {
+	versionRequirement string
+	release            release
+	matched            bool
+}
+
+func main() {
+	if len(os.Args) < 3 {
+		printUsage()
+		os.Exit(0)
+	}
+	binary := os.Args[1]
+	versionRequirement := os.Args[2]
+
+	if binary == "node" {
+		objects, err := listS3Objects("heroku-nodebin", "node")
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+		result, err := resolveNode(objects, getPlatform(), versionRequirement)
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+		if result.matched {
+			fmt.Printf("%s %s\n", result.release.version.String(), result.release.url)
+		} else {
+			fmt.Println("No result")
+			os.Exit(1)
+		}
+	} else if binary == "yarn" {
+		objects, err := listS3Objects("heroku-nodebin", "yarn")
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+		result, err := resolveYarn(objects, versionRequirement)
+		if err != nil {
+			fmt.Println(err)
+			os.Exit(1)
+		}
+		if result.matched {
+			fmt.Printf("%s %s\n", result.release.version.String(), result.release.url)
+		} else {
+			fmt.Println("No result")
+			os.Exit(1)
+		}
+	}
+}
+
+func printUsage() {
+	fmt.Println("resolve-version binary version-requirement")
+}
+
+func getPlatform() string {
+	if runtime.GOOS == "darwin" {
+		return "darwin-x64"
+	}
+	return "linux-x64"
+}
+
+func resolveNode(objects []s3Object, platform string, versionRequirement string) (matchResult, error) {
+	releases := []release{}
+	staging := []release{}
+
+	for _, obj := range objects {
+		release, err := parseObject(obj.Key)
+		if err != nil {
+			continue
+		}
+
+		// ignore any releases that are not for the given platform
+		if release.platform != platform {
+			continue
+		}
+
+		if release.stage == "release" {
+			releases = append(releases, release)
+		} else {
+			staging = append(staging, release)
+		}
+	}
+
+	result, err := matchReleaseSemver(releases, versionRequirement)
+	if err != nil {
+		return matchResult{}, err
+	}
+
+	// In order to accomodate integrated testing of staged Node binaries before they are
+	// released broadly, there is a special case where:
+	//
+	// - if there is no match to a Node binary AND
+	// - an exact version of a binary in `node/staging` is present
+	//
+	// the staging binary is used
+	if result.matched == false {
+		stagingResult := matchReleaseExact(staging, versionRequirement)
+		if stagingResult.matched {
+			return stagingResult, nil
+		}
+	}
+
+	return result, nil
+}
+
+func resolveYarn(objects []s3Object, versionRequirement string) (matchResult, error) {
+	releases := []release{}
+
+	for _, obj := range objects {
+		release, err := parseObject(obj.Key)
+		if err != nil {
+			continue
+		}
+
+		releases = append(releases, release)
+	}
+
+	return matchReleaseSemver(releases, versionRequirement)
+}
+
+func matchReleaseSemver(releases []release, versionRequirement string) (matchResult, error) {
+	rewrittenRequirement := rewriteRange(versionRequirement)
+	constraints, err := semver.NewConstraint(rewrittenRequirement)
+	if err != nil {
+		return matchResult{}, err
+	}
+
+	filtered := []release{}
+	for _, release := range releases {
+		if constraints.Check(release.version) {
+			filtered = append(filtered, release)
+		}
+	}
+
+	versions := make([]*semver.Version, len(filtered))
+	for i, rel := range filtered {
+		versions[i] = rel.version
+	}
+
+	coll := semver.Collection(versions)
+	sort.Sort(coll)
+
+	if len(coll) == 0 {
+		return matchResult{
+			versionRequirement: versionRequirement,
+			release:            release{},
+			matched:            false,
+		}, nil
+	}
+
+	resolvedVersion := coll[len(coll)-1]
+
+	for _, rel := range filtered {
+		if rel.version.Equal(resolvedVersion) {
+			return matchResult{
+				versionRequirement: versionRequirement,
+				release:            rel,
+				matched:            true,
+			}, nil
+		}
+	}
+	return matchResult{}, errors.New("Unknown error")
+}
+
+func matchReleaseExact(releases []release, version string) matchResult {
+	for _, release := range releases {
+		if release.version.String() == version {
+			return matchResult{
+				versionRequirement: version,
+				release:            release,
+				matched:            true,
+			}
+		}
+	}
+	return matchResult{
+		versionRequirement: version,
+		release:            release{},
+		matched:            false,
+	}
+}
+
+// Parses an S3 key into a struct of information about that release
+// Example input: node/release/linux-x64/node-v6.2.2-linux-x64.tar.gz
+func parseObject(key string) (release, error) {
+	nodeRegex := regexp.MustCompile("node\\/([^\\/]+)\\/([^\\/]+)\\/node-v([0-9]+\\.[0-9]+\\.[0-9]+)-([^.]*)(.*)\\.tar\\.gz")
+	yarnRegex := regexp.MustCompile("yarn\\/([^\\/]+)\\/yarn-v([0-9]+\\.[0-9]+\\.[0-9]+)\\.tar\\.gz")
+
+	if nodeRegex.MatchString(key) {
+		match := nodeRegex.FindStringSubmatch(key)
+		version, err := semver.NewVersion(match[3])
+		if err != nil {
+			return release{}, fmt.Errorf("Failed to parse version as semver:%s\n%s", match[3], err.Error())
+		}
+		return release{
+			binary:   "node",
+			stage:    match[1],
+			platform: match[2],
+			version:  version,
+			url:      fmt.Sprintf("https://s3.amazonaws.com/%s/node/%s/%s/node-v%s-%s.tar.gz", "heroku-nodebin", match[1], match[2], match[3], match[2]),
+		}, nil
+	}
+
+	if yarnRegex.MatchString(key) {
+		match := yarnRegex.FindStringSubmatch(key)
+		version, err := semver.NewVersion(match[2])
+		if err != nil {
+			return release{}, errors.New("Failed to parse version as semver")
+		}
+		return release{
+			binary:   "yarn",
+			stage:    match[1],
+			platform: "",
+			url:      fmt.Sprintf("https://s3.amazonaws.com/heroku-nodebin/yarn/release/yarn-v%s.tar.gz", version),
+			version:  version,
+		}, nil
+	}
+
+	return release{}, fmt.Errorf("Failed to parse key: %s", key)
+}
+
+// Wrapper around the S3 API for listing objects
+// This maps directly to the API and parses the XML response but will not handle
+// paging and offsets automaticaly
+func fetchS3Result(bucketName string, options map[string]string) (result, error) {
+	var result result
+	v := url.Values{}
+	v.Set("list-type", "2")
+	for key, val := range options {
+		v.Set(key, val)
+	}
+	url := fmt.Sprintf("https://%s.s3.amazonaws.com?%s", bucketName, v.Encode())
+	resp, err := http.Get(url)
+	if err != nil {
+		return result, err
+	}
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return result, err
+	}
+
+	return result, xml.Unmarshal(body, &result)
+}
+
+// Query the S3 API for a list of all the objects in an S3 bucket with a
+// given prefix. This will handle the inherent 1000 item limit and paging
+// for you
+func listS3Objects(bucketName string, prefix string) ([]s3Object, error) {
+	var out = []s3Object{}
+	var options = map[string]string{"prefix": prefix}
+
+	for {
+		result, err := fetchS3Result(bucketName, options)
+		if err != nil {
+			return nil, err
+		}
+
+		out = append(out, result.Contents...)
+		if !result.IsTruncated {
+			break
+		}
+
+		options["continuation-token"] = result.NextContinuationToken
+	}
+
+	return out, nil
+}
+
+// regex matching the semver version definitions
+// Ex:
+//    v1.0.0
+//    9
+//    8.x
+const cvRegex string = `v?([0-9|x|X|\*]+)(\.[0-9|x|X|\*]+)?(\.[0-9|x|X|\*]+)?` +
+	`(-([0-9A-Za-z\-]+(\.[0-9A-Za-z\-]+)*))?` +
+	`(\+([0-9A-Za-z\-]+(\.[0-9A-Za-z\-]+)*))?`
+
+// regex matching the semver operators
+const ops string = `=<|~>|!=|>|<|>=|=>|<=|\^|=|~`
+
+// Masterminds/semver does not support constraints like: `>1 <2`, preferring
+// `>1, <2` with a comma separator. This catches this particular case and
+// rewrites it
+func rewriteRange(c string) string {
+	constraintRangeRegex := regexp.MustCompile(fmt.Sprintf(
+		`^\s*(%s)(\s*%s)\s*(%s)(\s*%s)$`,
+		ops, cvRegex, ops, cvRegex,
+	))
+
+	ors := strings.Split(c, "||")
+	out := make([]string, len(ors))
+
+	for i, v := range ors {
+		m := constraintRangeRegex.FindStringSubmatch(v)
+		if m != nil {
+			out[i] = fmt.Sprintf("%s%s, %s%s", m[1], m[2], m[12], m[13])
+		} else {
+			out[i] = v
+		}
+	}
+
+	return strings.Join(out, `||`)
+}

cmd/resolve-version/main_integration_test.go

+// +build integration
+
+package main
+
+import (
+	"regexp"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestListS3Objects(t *testing.T) {
+	// Node
+	objects, err := listS3Objects("heroku-nodebin", "node")
+	assert.Nil(t, err)
+	assert.NotEmpty(t, objects)
+
+	// every returned result started with "node"
+	for _, obj := range objects {
+		assert.Regexp(t, regexp.MustCompile("^node"), obj.Key)
+	}
+
+	// every node object must parse as a valid release
+	for _, obj := range objects {
+		release, err := parseObject(obj.Key)
+		assert.Nil(t, err)
+		assert.Regexp(t, regexp.MustCompile("https:\\/\\/s3.amazonaws.com\\/heroku-nodebin"), release.url)
+		assert.Regexp(t, regexp.MustCompile("[0-9]+.[0-9]+.[0-9]+"), release.version.String())
+	}
+
+	// Yarn
+	objects, err = listS3Objects("heroku-nodebin", "yarn")
+	assert.Nil(t, err)
+	assert.NotEmpty(t, objects)
+
+	// every returned result started with "yarn"
+	for _, obj := range objects {
+		assert.Regexp(t, regexp.MustCompile("^yarn"), obj.Key)
+	}
+
+	// every yarn object must parse as a valid release
+	for _, obj := range objects {
+		release, err := parseObject(obj.Key)
+		assert.Nil(t, err)
+		assert.Regexp(t, regexp.MustCompile("https:\\/\\/s3.amazonaws.com\\/heroku-nodebin"), release.url)
+		assert.Regexp(t, regexp.MustCompile("[0-9]+.[0-9]+.[0-9]+"), release.version.String())
+	}
+}

etc/ci-setup.sh

@@ -2,7 +2,7 @@
 
 [ "$CI" != "true" ] && echo "Not running on CI!" && exit 1
 
-git config --global user.email ${HEROKU_API_USER:-"buildpack@example.com"}
+git config --global user.email "${HEROKU_API_USER:-"buildpack@example.com"}"
 git config --global user.name 'BuildpackTester'
 
 cat <<EOF >> ~/.ssh/config

etc/hatchet.sh

@@ -26,14 +26,16 @@ if [ -z "$HEROKU_API_KEY" ]; then
 fi
 
 if [ -n "$CIRCLE_BRANCH" ]; then
-  export HATCHET_BUILDPACK_BRANCH="$CIRCLE_BRANCH"
+  HATCHET_BUILDPACK_BRANCH="$CIRCLE_BRANCH"
 elif [ -n "$TRAVIS_PULL_REQUEST_BRANCH" ]; then
   export IS_RUNNING_ON_TRAVIS=true
-  export HATCHET_BUILDPACK_BRANCH="$TRAVIS_PULL_REQUEST_BRANCH"
+  HATCHET_BUILDPACK_BRANCH="$TRAVIS_PULL_REQUEST_BRANCH"
 else
-  export HATCHET_BUILDPACK_BRANCH=$(git name-rev HEAD 2> /dev/null | sed 's#HEAD\ \(.*\)#\1#' | sed 's#tags\/##')
+  HATCHET_BUILDPACK_BRANCH=$(git name-rev HEAD 2> /dev/null | sed 's#HEAD\ \(.*\)#\1#' | sed 's#tags\/##')
 fi
 
+export HATCHET_BUILDPACK_BRANCH
+
 gem install bundler
 bundle install
 

etc/publish.sh

@@ -7,7 +7,7 @@ BP_NAME=${1:-"heroku/nodejs"}
 curVersion=$(heroku buildpacks:versions "$BP_NAME" | awk 'FNR == 3 { print $1 }')
 newVersion="v$((curVersion + 1))"
 
-read -p "Deploy as version: $newVersion [y/n]? " choice
+read -r -p "Deploy as version: $newVersion [y/n]? " choice
 case "$choice" in
   y|Y ) echo "";;
   n|N ) exit 0;;

go.mod

+module github.com/heroku/heroku-buildpack-nodejs
+
+go 1.12
+
+require (
+	github.com/Masterminds/semver v1.4.2
+	github.com/stretchr/testify v1.3.0
+)

go.sum

+github.com/Masterminds/semver v1.4.2 h1:WBLTQ37jOCzSLtXNdoo8bNM8876KhNqOKvrlGITgsTc=
+github.com/Masterminds/semver v1.4.2/go.mod h1:MB6lktGJrhw8PrUyiEoblNEGEQ+RzHPF078ddwwvV3Y=
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=

lib/binaries.sh

+#!/usr/bin/env bash
+
+RESOLVE="$BP_DIR/vendor/resolve-version-$(get_os)"
+
 install_yarn() {
   local dir="$1"
   local version=${2:-1.x}
-  local number
-  local url
+  local platform="$3"
+  local number url code nodebin_result resolve_result
 
   echo "Resolving yarn version $version..."
-  if ! read number url < <(curl --silent --get --retry 5 --retry-max-time 15 --data-urlencode "range=$version" "https://nodebin.jxltom.com/v1/yarn/$platform/latest.txt"); then
-    fail_bin_install yarn $version;
+  nodebin_result=$(curl --fail --silent --get --retry 5 --retry-max-time 15 --data-urlencode "range=$version" "https://nodebin.jxltom.com/v1/yarn/$platform/latest.txt" || echo "failed")
+  resolve_result=$($RESOLVE yarn "$version" || echo "failed")
+
+  if [[ "$nodebin_result" == "failed" ]]; then
+    fail_bin_install yarn "$version" "$platform"
+  fi
+
+  read -r number url < <(echo "$nodebin_result")
+
+  # log out whether the new logic matches the old logic
+  if [[ "$nodebin_result" != "$resolve_result" ]]; then
+    meta_set "resolve-matches-nodebin-yarn" "false"
+  else
+    meta_set "resolve-matches-nodebin-yarn" "true"
+  fi
+
+  # log out when the new logic fails
+  if [[ "$resolve_result" == "failed" ]]; then
+    meta_set "resolve-failed-yarn" "true"
   fi
 
   echo "Downloading and installing yarn ($number)..."
-  local code=$(curl "$url" -L --silent --fail --retry 5 --retry-max-time 15 -o /tmp/yarn.tar.gz --write-out "%{http_code}")
+  code=$(curl "$url" -L --silent --fail --retry 5 --retry-max-time 15 -o /tmp/yarn.tar.gz --write-out "%{http_code}")
   if [ "$code" != "200" ]; then
     echo "Unable to download yarn: $code" && false
   fi
-  rm -rf $dir
+  rm -rf "$dir"
   mkdir -p "$dir"
   # https://github.com/yarnpkg/yarn/issues/770
   if tar --version | grep -q 'gnu'; then
@@ -22,54 +43,58 @@ install_yarn() {
   else
     tar xzf /tmp/yarn.tar.gz -C "$dir" --strip 1
   fi
-  chmod +x $dir/bin/*
+  chmod +x "$dir"/bin/*
   echo "Installed yarn $(yarn --version)"
 }
 
 install_nodejs() {
   local version=${1:-10.x}
   local dir="${2:?}"
+  local platform="$3"
+  local code os cpu nodebin_result resolve_result
+
+  os=$(get_os)
+  cpu=$(get_cpu)
 
   echo "Resolving node version $version..."
-  if ! read number url < <(curl --silent --get --retry 5 --retry-max-time 15 --data-urlencode "range=$version" "https://nodebin.jxltom.com/v1/node/$platform/latest.txt"); then
-    fail_bin_install node $version;
-  fi
+  nodebin_result=$(curl --silent --fail --get --retry 5 --retry-max-time 15 --data-urlencode "range=$version" "https://nodebin.jxltom.com/v1/node/$platform/latest.txt" || echo "failed")
+  resolve_result=$($RESOLVE node "$version" || echo "failed")
 
-  echo "Downloading and installing node $number..."
-  local code=$(curl "$url" -L --silent --fail --retry 5 --retry-max-time 15 -o /tmp/node.tar.gz --write-out "%{http_code}")
-  if [ "$code" != "200" ]; then
-    echo "Unable to download node: $code" && false
+  read -r number url < <(echo "$nodebin_result")
+
+  if [[ "$nodebin_result" == "failed" ]]; then
+    fail_bin_install node "$version" "$platform"
   fi
-  tar xzf /tmp/node.tar.gz -C /tmp
-  rm -rf "$dir"/*
-  mv /tmp/node-v$number-$os-$cpu/* $dir
-  chmod +x $dir/bin/*
-}
 
-install_iojs() {
-  local version="$1"
-  local dir="$2"
+  # log out whether the new logic matches the old logic
+  if [[ "$nodebin_result" != "$resolve_result" ]]; then
+    meta_set "resolve-matches-nodebin-node" "false"
+  else
+    meta_set "resolve-matches-nodebin-node" "true"
+  fi
 
-  echo "Resolving iojs version ${version:-(latest stable)}..."
-  if ! read number url < <(curl --silent --get --retry 5 --retry-max-time 15 --data-urlencode "range=$version" "https://nodebin.jxltom.com/v1/iojs/$platform/latest.txt"); then
-    fail_bin_install iojs $version;
+  # log out when the new logic fails
+  if [[ "$resolve_result" == "failed" ]]; then
+    meta_set "resolve-failed-node" "true"
   fi
 
-  echo "Downloading and installing iojs $number..."
-  local code=$(curl "$url" --silent --fail --retry 5 --retry-max-time 15 -o /tmp/iojs.tar.gz --write-out "%{http_code}")
+  echo "Downloading and installing node $number..."
+  code=$(curl "$url" -L --silent --fail --retry 5 --retry-max-time 15 -o /tmp/node.tar.gz --write-out "%{http_code}")
   if [ "$code" != "200" ]; then
-    echo "Unable to download iojs: $code" && false
+    echo "Unable to download node: $code" && false
   fi
-  tar xzf /tmp/iojs.tar.gz -C /tmp
-  mv /tmp/iojs-v$number-$os-$cpu/* $dir
-  chmod +x $dir/bin/*
+  tar xzf /tmp/node.tar.gz -C /tmp
+  rm -rf "${dir:?}"/*
+  mv /tmp/node-v"$number"-"$os"-"$cpu"/* "$dir"
+  chmod +x "$dir"/bin/*
 }
 
 install_npm() {
+  local npm_version
   local version="$1"
   local dir="$2"
   local npm_lock="$3"
-  local npm_version="$(npm --version)"
+  npm_version="$(npm --version)"
 
   # If the user has not specified a version of npm, but has an npm lockfile
   # upgrade them to npm 5.x if a suitable version was not installed with Node

lib/build-data.sh

-# variable shared by this whole module
-BUILD_DATA_FILE=""
-
-bd_create() {
-  local cache_dir="$1"
-  BUILD_DATA_FILE="$cache_dir/build-data/node"
-  kv_create $BUILD_DATA_FILE
-}
-
-bd_get() {
-  kv_get $BUILD_DATA_FILE "$1"
-}
-
-bd_set() {
-  kv_set $BUILD_DATA_FILE "$1" "$2"
-}
-
-log_build_data() {
-  # print all values on one line in logfmt format
-  # https://brandur.org/logfmt
-  echo $(kv_list $BUILD_DATA_FILE)
-}

lib/builddata.sh

+#!/usr/bin/env bash
+
+log_initial_state() {
+  meta_set "buildpack" "nodejs"
+  if "$YARN"; then
+    meta_set "node-package-manager" "yarn"
+    meta_set "has-node-lock-file" "true"
+  else
+    meta_set "node-package-manager" "npm"
+    meta_set "has-node-lock-file" "$NPM_LOCK"
+  fi
+
+  meta_set "stack" "$STACK"
+}
+
+generate_uuids() {
+  # generate a unique id for each build
+  meta_set "build-uuid" "$(uuid)"
+
+  # propagate an app-uuid forward unless the cache is cleared
+  if [[ -n "$(meta_prev_get "app-uuid")" ]]; then
+    meta_set "app-uuid" "$(meta_prev_get "app-uuid")"
+  else
+    meta_set "app-uuid" "$(uuid)"
+  fi
+}
+
+log_build_script_opt_in() {
+  local opted_in="$1"
+  local build_dir="$2"
+  local has_build_script has_heroku_build_script
+
+  has_build_script=$(read_json "$build_dir/package.json" ".scripts.build")
+  has_heroku_build_script=$(read_json "$build_dir/package.json" ".scripts[\"heroku-postbuild\"]")
+
+  # if this app will be affected by the change
+  if [[ -z "$has_heroku_build_script" ]] && [[ -n "$has_build_script" ]]; then
+    mcount "affected-by-build-change"
+
+    if [[ "$opted_in" = "true" ]]; then
+      mcount "affected-by-build-change-opted-in"
+      meta_set "affected-but-opted-in" "true"
+    else
+      meta_set "affected-but-opted-in" "false"
+    fi
+
+  fi
+
+  if [[ "$opted_in" = true ]]; then
+    meta_set "build-script-opt-in" "true"
+  else
+    meta_set "build-script-opt-in" "false"
+  fi
+}
\ No newline at end of file

lib/cache.sh

-source $BP_DIR/lib/binaries.sh
+#!/usr/bin/env bash
 
 create_signature() {
   echo "v2; ${STACK}; $(node --version); $(npm --version); $(yarn --version 2>/dev/null || true); ${PREBUILD}"
 }
 
 save_signature() {
-  create_signature > $CACHE_DIR/node/signature
+  local cache_dir="$1"
+  create_signature > "$cache_dir/node/signature"
 }
 
 load_signature() {
-  if test -f $CACHE_DIR/node/signature; then
-    cat $CACHE_DIR/node/signature
+  local cache_dir="$1"
+  if test -f "$cache_dir/node/signature"; then
+    cat "$cache_dir/node/signature"
   else
     echo ""
   fi
 }
 
 get_cache_status() {
+  local cache_dir="$1"
   if ! ${NODE_MODULES_CACHE:-true}; then
     echo "disabled"
-  elif ! test -d "${CACHE_DIR}/node/"; then
+  elif ! test -d "$cache_dir/node/"; then
     echo "not-found"
-  elif [ "$(create_signature)" != "$(load_signature)" ]; then
+  elif [ "$(create_signature)" != "$(load_signature "$cache_dir")" ]; then
     echo "new-signature"
   else
     echo "valid"
@@ -29,8 +32,10 @@ get_cache_status() {
 }
 
 get_cache_directories() {
-  local dirs1=$(read_json "$BUILD_DIR/package.json" ".cacheDirectories | .[]?")
-  local dirs2=$(read_json "$BUILD_DIR/package.json" ".cache_directories | .[]?")
+  local build_dir="$1"
+  local dirs1 dirs2
+  dirs1=$(read_json "$build_dir/package.json" ".cacheDirectories | .[]?")
+  dirs2=$(read_json "$build_dir/package.json" ".cache_directories | .[]?")
 
   if [ -n "$dirs1" ]; then
     echo "$dirs1"
@@ -61,9 +66,11 @@ restore_default_cache_directories() {
 }
 
 restore_custom_cache_directories() {
+  local cache_directories
   local build_dir=${1:-}
   local cache_dir=${2:-}
-  local cache_directories=("${@:3}")
+  # Parse the input string with multiple lines: "a\nb\nc" into an array
+  mapfile -t cache_directories <<< "$3"
 
   echo "Loading ${#cache_directories[@]} from cacheDirectories (package.json):"
 
@@ -83,9 +90,10 @@ restore_custom_cache_directories() {
 }
 
 clear_cache() {
-  rm -rf $CACHE_DIR/node
-  mkdir -p $CACHE_DIR/node
-  mkdir -p $CACHE_DIR/node/cache
+  local cache_dir="$1"
+  rm -rf "$cache_dir/node"
+  mkdir -p "$cache_dir/node"
+  mkdir -p "$cache_dir/node/cache"
 }
 
 save_default_cache_directories() {
@@ -106,16 +114,21 @@ save_default_cache_directories() {
   # bower_components
   if [[ -e "$build_dir/bower_components" ]]; then
     mcount "cache.saved-bower-components"
+    meta_set "cached-bower-components" "true"
     echo "- bower_components"
     mkdir -p "$cache_dir/node/cache/bower_components"
     cp -a "$build_dir/bower_components" "$(dirname "$cache_dir/node/cache/bower_components")"
   fi
+
+  meta_set "node-custom-cache-dirs" "false"
 }
 
 save_custom_cache_directories() {
+  local cache_directories
   local build_dir=${1:-}
   local cache_dir=${2:-}
-  local cache_directories=("${@:3}")
+  # Parse the input string with multiple lines: "a\nb\nc" into an array
+  mapfile -t cache_directories <<< "$3"
 
   echo "Saving ${#cache_directories[@]} cacheDirectories (package.json):"
 
@@ -128,4 +141,6 @@ save_custom_cache_directories() {
       echo "- $cachepath (nothing to cache)"
     fi
   done
+
+  meta_set "node-custom-cache-dirs" "true"
 }

lib/environment.sh

+#!/usr/bin/env bash
+
 get_os() {
-  uname | tr A-Z a-z
+  uname | tr '[:upper:]' '[:lower:]'
 }
 
 get_cpu() {
@@ -10,10 +12,11 @@ get_cpu() {
   fi
 }
 
-os=$(get_os)
-cpu=$(get_cpu)
-platform="$os-$cpu"
-export JQ="$BP_DIR/vendor/jq-$os"
+get_platform() {
+  os=$(get_os)
+  cpu=$(get_cpu)
+  echo "$os-$cpu"
+}
 
 create_default_env() {
   export NPM_CONFIG_LOGLEVEL=${NPM_CONFIG_LOGLEVEL:-error}
@@ -54,13 +57,15 @@ export_env_dir() {
   if [ -d "$env_dir" ]; then
     local whitelist_regex=${2:-''}
     local blacklist_regex=${3:-'^(PATH|GIT_DIR|CPATH|CPPATH|LD_PRELOAD|LIBRARY_PATH|LANG|BUILD_DIR)$'}
+    # shellcheck disable=SC2164
     pushd "$env_dir" >/dev/null
     for e in *; do
       [ -e "$e" ] || continue
       echo "$e" | grep -E "$whitelist_regex" | grep -qvE "$blacklist_regex" &&
-      export "$e=$(cat $e)"
+      export "$e=$(cat "$e")"
       :
     done
+    # shellcheck disable=SC2164
     popd >/dev/null
   fi
 }
@@ -68,15 +73,15 @@ export_env_dir() {
 write_profile() {
   local bp_dir="$1"
   local build_dir="$2"
-  mkdir -p $build_dir/.profile.d
-  cp $bp_dir/profile/* $build_dir/.profile.d/
+  mkdir -p "$build_dir/.profile.d"
+  cp "$bp_dir"/profile/* "$build_dir/.profile.d/"
 }
 
 write_ci_profile() {
   local bp_dir="$1"
   local build_dir="$2"
   write_profile "$1" "$2"
-  cp $bp_dir/ci-profile/* $build_dir/.profile.d/
+  cp "$bp_dir"/ci-profile/* "$build_dir/.profile.d/"
 }
 
 write_export() {
@@ -86,8 +91,8 @@ write_export() {
   # only write the export script if the buildpack directory is writable.
   # this may occur in situations outside of Heroku, such as running the
   # buildpacks locally.
-  if [ -w ${bp_dir} ]; then
-    echo "export PATH=\"$build_dir/.heroku/node/bin:$build_dir/.heroku/yarn/bin:\$PATH:$build_dir/node_modules/.bin\"" > $bp_dir/export
-    echo "export NODE_HOME=\"$build_dir/.heroku/node\"" >> $bp_dir/export
+  if [ -w "$bp_dir" ]; then
+    echo "export PATH=\"$build_dir/.heroku/node/bin:$build_dir/.heroku/yarn/bin:\$PATH:$build_dir/node_modules/.bin\"" > "$bp_dir/export"
+    echo "export NODE_HOME=\"$build_dir/.heroku/node\"" >> "$bp_dir/export"
   fi
 }

lib/experiments.sh

+#!/usr/bin/env bash
+
+# This module is designed to be able to roll out experiments to a
+# random segment of users for A/B testing. This takes as input a
+# list of experiments along with % chance they will be enabled,
+# decides which to enable, and persists these decisions into the
+# application cache.
+#
+# This module takes in no outside data, so it is limited in it's
+# uses. While an experiment can be persisted between builds for the
+# same app, it cannot be consistent for a given user / team. Even
+# different PR apps will be decided independently.
+#
+# This means that this should not be used for changing the build 
+# behavior of the buildpack. Builds should always work consistently
+# no matter what experiments are turned on or off.
+#
+# Where this module can be useful is when deciding between two 
+# identical behaviors that may have performance trade-offs, or
+# testing the efficacy of different messaging. 
+#
+# Examples: 
+#    testing two different caching strategies against each other
+#    showing guidance on a particular type of failure
+#
+# It is expected that these experiments will be short-lived
+#
+# Schema
+#
+# This module expects a "schema" file as input. This is used to
+# make sure that all current experiments are documented in one 
+# place. The file is a list of key=value pairs on individual 
+# lines.
+#
+# There is a special "#version" key that is expected that can be
+# used to invalidate any existing experiments.
+#
+# The key is the name, and the value is an integery between 0 and
+# 100 inclusive that represents the likelyhood that the experiment
+# will be turned on for any given app.
+#
+# Example:
+# ```
+# #version=1
+# always-on=100   // this will always be turned on, not super useful
+# ab-test=50      // this will be split 50/50
+# small-test=5    // this will be turned on for 5% of apps
+# ```
+#
+# See tests/unit-fixtures/experiments/experiments-v1 for an example
+
+# variables shared by this whole module
+EXPERIMENTS_DATA_FILE=""
+
+experiments_init() {
+  local name="$1"
+  local cache_dir="$2"
+  local schema="$3"
+
+  local last_schema_version schema_version random odds
+
+  EXPERIMENTS_DATA_FILE="$cache_dir/experiments/$name"
+
+  last_schema_version="$(kv_get "$EXPERIMENTS_DATA_FILE" "#version")"
+  schema_version="$(kv_get "$schema" "#version")"
+
+  # If the schema has changed, blow away the current values
+  # and start fresh. This is essentially "wiping the slate clean"
+  # and no previous experiments will be enabled for anyone
+  #
+  # In the case that the schema version is the same, we keep
+  # all of the previously decided experiments (file is the same)
+  # and decide on any new ones
+  if [[ "$last_schema_version" != "$schema_version" ]]; then
+    kv_create "$EXPERIMENTS_DATA_FILE"
+    kv_clear "$EXPERIMENTS_DATA_FILE"
+    # save out the version we're using to generate this set of experiments
+    kv_set "$EXPERIMENTS_DATA_FILE" "#version" "$schema_version"
+  fi
+
+  # iterate through the schema and decide if each new experiment
+  # should be turned on or not
+  kv_keys "$schema" | tr ' ' '\n' | while read -r key; do
+    # skip the special version key
+    if [[ "$key" = "#version" ]]; then
+      continue
+    # skip any values that are already decided
+    elif [[ -n "$(kv_get "$EXPERIMENTS_DATA_FILE" "$key")" ]]; then
+      continue
+    else
+      # generate a random number between 0 and 100
+      random=$((RANDOM % 100))
+      # the value in the schema should be a number between 0 and 100 inclusive
+      odds=$(kv_get "$schema" "$key")
+      if [[ "$random" -lt "$odds" ]]; then
+        kv_set "$EXPERIMENTS_DATA_FILE" "$key" "true"
+      else
+        kv_set "$EXPERIMENTS_DATA_FILE" "$key" "false"
+      fi
+    fi
+  done
+}
+
+# Determine whether an experiment is enabled or disabled
+# Must call experiments_init first
+#
+# Possible outputs: "true" "false" ""
+experiments_get() {
+  kv_get "$EXPERIMENTS_DATA_FILE" "$1"
+}
+
+# Outputs a list of experiment names, one-per-line
+experiments_list() {
+  kv_keys "$EXPERIMENTS_DATA_FILE"
+}

lib/json.sh

+#!/usr/bin/env bash
+
+JQ="$BP_DIR/vendor/jq-$(get_os)"
+
 read_json() {
-  local file=$1
-  local key=$2
-  if test -f $file; then
-    cat $file | $JQ --raw-output "$key // \"\"" || return 1
+  local file="$1"
+  local key="$2"
+
+  if test -f "$file"; then
+    # shellcheck disable=SC2002
+    cat "$file" | $JQ --raw-output "$key // \"\"" || return 1
   else
     echo ""
   fi
 }
+
+has_script() {
+  local file="$1"
+  local key="$2"
+
+  if test -f "$file"; then
+    # shellcheck disable=SC2002
+    cat "$file" | $JQ ".[\"scripts\"] | has(\"$key\")"
+  else
+    echo "false"
+  fi
+}
+
+is_invalid_json_file() {
+  local file="$1"
+  # shellcheck disable=SC2002
+  if ! cat "$file" | $JQ "." 1>/dev/null; then
+    echo "true"
+  else
+    echo "false"
+  fi
+}
\ No newline at end of file

lib/kvstore.sh

+#!/usr/bin/env bash
 
 kv_create() {
   local f=$1
-  mkdir -p $(dirname $f)
-  touch $f
+  mkdir -p "$(dirname "$f")"
+  touch "$f"
 }
 
 kv_clear() {
   local f=$1
-  echo "" > $f
+  echo "" > "$f"
 }
 
 kv_set() {
   if [[ $# -eq 3 ]]; then
     local f=$1
     if [[ -f $f ]]; then
-      echo "$2=$3" >> $f
+      echo "$2=$3" >> "$f"
     fi
   fi
 }
 
-# get the value, but don't unwrap quotes
 kv_get() {
   if [[ $# -eq 2 ]]; then
     local f=$1
     if [[ -f $f ]]; then
-      grep "^$2=" $f | sed -e "s/^$2=//" | tail -n 1
+      grep "^$2=" "$f" | sed -e "s/^$2=//" | tail -n 1
     fi
   fi
 }
 
+# get the value, but wrap it in quotes if it contains a space
 kv_get_escaped() {
-  local value=$(kv_get $1 $2 $3)
+  local value
+  value=$(kv_get "$1" "$2")
   if [[ $value =~ [[:space:]]+ ]]; then
     echo "\"$value\""
   else
-    echo $value
+    echo "$value"
   fi
 }
 
@@ -43,10 +45,18 @@ kv_keys() {
   local keys=()
 
   if [[ -f $f ]]; then
-    # get list of keys
-    while IFS="=" read -r key value; do
-      keys+=("$key")
-    done < $f
+    # Iterate over each line, splitting on the '=' character
+    #
+    # The || [[ -n "$key" ]] statement addresses an issue with reading the last line
+    # of a file when there is no newline at the end. This will not happen if the file
+    # is created with this module, but can happen if it is written by hand.
+    # See: https://stackoverflow.com/questions/12916352/shell-script-read-missing-last-line
+    while IFS="=" read -r key value || [[ -n "$key" ]]; do
+      # if there are any empty lines in the store, skip them
+      if [[ -n $key ]]; then
+        keys+=("$key")
+      fi
+    done < "$f"
 
     echo "${keys[@]}" | tr ' ' '\n' | sort -u
   fi
@@ -55,9 +65,9 @@ kv_keys() {
 kv_list() {
   local f=$1
 
-  kv_keys $f | tr ' ' '\n' | while read -r key; do
+  kv_keys "$f" | tr ' ' '\n' | while read -r key; do
     if [[ -n $key ]]; then
-      echo "$key=$(kv_get_escaped $f $key)"
+      echo "$key=$(kv_get_escaped "$f" "$key")"
     fi
   done
 }

lib/metadata.sh

+#!/usr/bin/env bash
+
+# variable shared by this whole module
+BUILD_DATA_FILE=""
+PREVIOUS_BUILD_DATA_FILE=""
+
+meta_create() {
+  local cache_dir="$1"
+  BUILD_DATA_FILE="$cache_dir/build-data/nodejs"
+  PREVIOUS_BUILD_DATA_FILE="$cache_dir/build-data/nodejs-prev"
+
+  # if the file already exists because it's from the last build, save it
+  if [[ -f "$BUILD_DATA_FILE" ]]; then
+    cp "$BUILD_DATA_FILE" "$PREVIOUS_BUILD_DATA_FILE"
+  fi
+
+  kv_create "$BUILD_DATA_FILE"
+  # make sure this doesnt grow over time
+  kv_clear "$BUILD_DATA_FILE"
+}
+
+meta_get() {
+  kv_get "$BUILD_DATA_FILE" "$1"
+}
+
+meta_set() {
+  kv_set "$BUILD_DATA_FILE" "$1" "$2"
+}
+
+# similar to mtime from stdlib
+meta_time() {
+  local key="$1"
+  local start="$2"
+  local end="${3:-$(nowms)}"
+  local time
+  time="$(echo "${start}" "${end}" | awk '{ printf "%.3f", ($2 - $1)/1000 }')"
+  kv_set "$BUILD_DATA_FILE" "$key" "$time"
+}
+
+# similar to mtime from stdlib
+meta_time() {
+  local key="$1"
+  local start="$2"
+  local end="${3:-$(nowms)}"
+  local time
+  time="$(echo "$start" "$end" | awk '{ printf "%.3f", ($2 - $1)/1000 }')"
+  kv_set "$BUILD_DATA_FILE" "$1" "$time"
+}
+
+# Retrieve a value from a previous build if it exists
+# This is useful to give the user context about what changed if the 
+# build has failed. Ex:
+#   - changed stacks
+#   - deployed with a new major version of Node
+#   - etc
+meta_prev_get() {
+  kv_get "$PREVIOUS_BUILD_DATA_FILE" "$1"
+}
+
+log_meta_data() {
+  # print all values on one line in logfmt format
+  # https://brandur.org/logfmt
+  # the echo call ensures that all values are printed on a single line
+  # shellcheck disable=SC2005 disable=SC2046
+  echo $(kv_list "$BUILD_DATA_FILE")
+}

lib/monitor.sh

+#!/usr/bin/env bash
 
 monitor_memory_usage() {
   local output_file="$1"
@@ -12,7 +13,7 @@ monitor_memory_usage() {
   pid=$!
 
   # if this build process is SIGTERM'd
-  trap "kill -TERM $pid" TERM
+  trap 'kill -TERM $pid' TERM
 
   # set the peak memory usage to 0 to start
   peak="0"
@@ -29,7 +30,7 @@ monitor_memory_usage() {
   done
 
   # ps gives us kb, let's convert to mb for convenience
-  echo "$(($peak / 1024))" > $output_file
+  echo "$((peak / 1024))" > "$output_file"
 
   # After wait returns we can get the exit code of $command
   wait $pid
@@ -43,16 +44,21 @@ monitor_memory_usage() {
 }
 
 monitor() {
+  local peak_mem_output start
   local command_name=$1
   shift
 
   local command=( "$@" )
-  local peak_mem_output=$(mktemp)
-  local start=$(nowms)
+
+  peak_mem_output=$(mktemp)
+  start=$(nowms)
 
   # execute the subcommand and save the peak memory usage
-  monitor_memory_usage $peak_mem_output "${command[@]}"
+  monitor_memory_usage "$peak_mem_output" "${command[@]}"
 
   mtime "exec.$command_name.time" "${start}"
-  mmeasure "exec.$command_name.memory" "$(cat $peak_mem_output)"
+  mmeasure "exec.$command_name.memory" "$(cat "$peak_mem_output")"
+
+  meta_time "$command_name-time" "$start"
+  meta_set "$command_name-memory" "$(cat "$peak_mem_output")"
 }

lib/output.sh

+#!/usr/bin/env bash
+
 # TODO: Merge these with the output helpers in buildpack-stdlib:
 # https://github.com/heroku/buildpack-stdlib
 
@@ -26,6 +28,15 @@ header() {
   echo "-----> $*" || true
 }
 
+bright_header() {
+  echo "" || true
+  echo -e "\033[1;33m-----> $* \033[0m"
+}
+
+header_skip_newline() {
+  echo "-----> $*" || true
+}
+
 error() {
   echo " !     $*" >&2 || true
   echo "" || true

lib/plugin.sh

+#!/usr/bin/env bash
 
 get_node_major_version() {
-  local node_version="$(node --version)"
+  local node_version
+
+  node_version="$(node --version)"
   # major_string will be ex: "6." "8." "10"
   local major_string=${node_version:1:2}
   # strip any "."s from major_string
   local major=${major_string//.}
-  echo $major
+  echo "$major"
 }
 
 install_plugin() {
+  local major
   local bp_dir="$1"
   local build_dir="$2"
-  local major=$(get_node_major_version)
+  major=$(get_node_major_version)
   local plugin="${bp_dir}/plugin/heroku-nodejs-plugin-node-${major}.tar.gz"
 
   # If we have a version of the plugin compiled for this version of node, and the
@@ -19,6 +23,6 @@ install_plugin() {
   # It will be included at runtime once the user opts into the Node metrics feature
   if [[ -f "${plugin}" ]] && [[ -z "$HEROKU_SKIP_NODE_PLUGIN" ]]; then
     mkdir -p "${build_dir}/.heroku/"
-    tar -xzf ${plugin} -C "${build_dir}/.heroku/"
+    tar -xzf "${plugin}" -C "${build_dir}/.heroku/"
   fi
 }

lib/uuid.sh

+#!/usr/bin/env bash
+
+uuid_fallback()
+{
+    local N B C='89ab'
+
+    for (( N=0; N < 16; ++N ))
+    do
+        B=$(( RANDOM%256 ))
+
+        case $N in
+            6)
+                printf '4%x' $(( B%16 ))
+                ;;
+            8)
+                printf '%c%x' ${C:$RANDOM%${#C}:1} $(( B%16 ))
+                ;;
+            3 | 5 | 7 | 9)
+                printf '%02x-' $B
+                ;;
+            *)
+                printf '%02x' $B
+                ;;
+        esac
+    done
+
+    echo
+}
+
+uuid() {
+  # On Heroku's stack, there is a uuid command
+  if [[ -f /proc/sys/kernel/random/uuid ]]; then
+    cat /proc/sys/kernel/random/uuid
+  # on macOS there is also a command
+  elif [[ -x "$(command -v uuidgen)" ]]; then
+    uuidgen | tr "[:upper:]" "[:lower:]"
+  # If you are running this buildpack on an image without either of the above binaries
+  # then let's provide something that approximates this functionality, but beware that
+  # we can make no guarantees of true randomness or uniqueness of this ID. However it is
+  # likely only being piped to /dev/null
+  #
+  # If that's not true for you, please file an issue and let us know: 
+  # https://github.com/heroku/heroku-buildpack-nodejs/issues
+  else
+    uuid_fallback
+  fi
+}

makefile

 test: heroku-18 heroku-16 cedar-14
 
+build:
+	@GOOS=darwin GOARCH=amd64 go build -ldflags="-s -w" -v -o ./vendor/resolve-version-darwin ./cmd/resolve-version
+	@GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -v -o ./vendor/resolve-version-linux ./cmd/resolve-version
+
+build-production:
+	# build go binaries and then compress them
+	@GOOS=darwin GOARCH=amd64 go build -ldflags="-s -w" -v -o ./vendor/resolve-version-darwin ./cmd/resolve-version
+	@GOOS=linux GOARCH=amd64 go build -ldflags="-s -w" -v -o ./vendor/resolve-version-linux ./cmd/resolve-version
+	# https://blog.filippo.io/shrink-your-go-binaries-with-this-one-weird-trick/
+	upx --brute vendor/resolve-version-linux
+	upx --brute vendor/resolve-version-darwin
+
+test-binary:
+	go test -v ./cmd/... -tags=integration
+
+shellcheck:
+	@shellcheck -x bin/compile bin/detect bin/release bin/test bin/test-compile
+	@shellcheck -x lib/**
+	@shellcheck -x ci-profile/**
+	@shellcheck -x etc/**
+
 heroku-18:
 	@echo "Running tests in docker (heroku-18)..."
 	@docker run -v $(shell pwd):/buildpack:ro --rm -it -e "STACK=heroku-18" heroku/heroku:18 bash -c 'cp -r /buildpack /buildpack_test; cd /buildpack_test/; test/run;'

plugin/download.sh

@@ -8,7 +8,7 @@ TAG_NAME=${1:-}
 PLUGIN_DIR=$(dirname $0)
 
 handle_failure() {
-    echo "Failure running script."
+    echo "Failure running script on line $1."
 
     
     echo "This may be rate-limiting from Github if you've run this script a few times. Here is the rate limit response:"
@@ -34,6 +34,8 @@ download() {
 
 delete_old_plugin() {
     local dir=${1}
+    rm -f "$dir/heroku-nodejs-plugin-node-12.sha512"
+    rm -f "$dir/heroku-nodejs-plugin-node-12.tar.gz"
     rm -f "$dir/heroku-nodejs-plugin-node-11.sha512"
     rm -f "$dir/heroku-nodejs-plugin-node-11.tar.gz"
     rm -f "$dir/heroku-nodejs-plugin-node-10.sha512"
@@ -64,6 +66,10 @@ download_assets_for_release() {
     # Node 11
     download "https://github.com/heroku/heroku-nodejs-plugin/releases/download/$tag/heroku-nodejs-plugin-node-11-$tag.sha512" "$dir/heroku-nodejs-plugin-node-11.sha512"
     download "https://github.com/heroku/heroku-nodejs-plugin/releases/download/$tag/heroku-nodejs-plugin-node-11-$tag.tar.gz" "$dir/heroku-nodejs-plugin-node-11.tar.gz"
+
+    # Node 12
+    download "https://github.com/heroku/heroku-nodejs-plugin/releases/download/$tag/heroku-nodejs-plugin-node-12-$tag.sha512" "$dir/heroku-nodejs-plugin-node-12.sha512"
+    download "https://github.com/heroku/heroku-nodejs-plugin/releases/download/$tag/heroku-nodejs-plugin-node-12-$tag.tar.gz" "$dir/heroku-nodejs-plugin-node-12.tar.gz"
 }
 
 test_hash() {
@@ -81,7 +87,7 @@ test_hash() {
     fi
 }
 
-trap 'handle_failure' ERR
+trap 'handle_failure ${LINENO}' ERR
 
 if [[ -z $TAG_NAME ]]; then
     TAG_NAME=$(get_latest_release)
@@ -100,5 +106,6 @@ test_hash 8 $PLUGIN_DIR
 test_hash 9 $PLUGIN_DIR
 test_hash 10 $PLUGIN_DIR
 test_hash 11 $PLUGIN_DIR
+test_hash 12 $PLUGIN_DIR
 
 echo "Done"

plugin/heroku-nodejs-plugin-node-10.sha512

-10e91fb8f741a42226fe91daf41a30032f6950f560622ce4523766d93dfd9d01dc88b3d5bfb26968d69d5f8fb6c61f0b35db310f61c366ae0c8d48c9181ee02c  heroku-nodejs-plugin-node-10-v4.tar.gz
+d6ad0f45d5564f324147f590ce9ac39c5973a64dfb1905eb993dfcf3dce21b6934a7821ffbd853ff30e89952ba17e7667809152e187453d7c18579d945a5f8bd  heroku-nodejs-plugin-node-10-v5.tar.gz

plugin/heroku-nodejs-plugin-node-11.sha512

-6d0732e32f6cb2a818c415c5fc454912113da273c3b158124c630db473aa0b157fc81c41dd90de887a804e3c2c2eae0b9897d0da329b7a6e52b9cf27db4e5d0a  heroku-nodejs-plugin-node-11-v4.tar.gz
+0afc36d4268b7ce3dd1c59813d7727a1bae715645bc0fb006ca992ccd028df692e31d2a4df697ab08d6b4baad03cd6ebef8525e481e0c5cf12e810c30e1da0cb  heroku-nodejs-plugin-node-11-v5.tar.gz

plugin/heroku-nodejs-plugin-node-12.sha512

+0020b60fd3aebcc1fb13770e3445a93c0633579853ee0d31d3dc12d02e4a8a1d418a4d4add2145da46f9d2820f6ae1e412a0beb4eb3e46d7fc8326d2e2d8248d  heroku-nodejs-plugin-node-12-v5.tar.gz

plugin/heroku-nodejs-plugin-node-8.sha512

-82a7f67bf61490d40aa69455a6a1fd7459f9fc219dfe9b0ac65cf7345e8a1c10070ce96ef42eecc5eb82fb5d7ea74b69e1a060c44f0a438eb02e81fd109c2ea4  heroku-nodejs-plugin-node-8-v4.tar.gz
+d96566824853bc7657fbf2f651067ed0b1747e4d6b4b9b443df6f2d490742b4e571dff5165e68c6d8af44501af0bdddd98e71eeb5fcc9816348453a1f8a314d9  heroku-nodejs-plugin-node-8-v5.tar.gz

plugin/heroku-nodejs-plugin-node-9.sha512

-d7bca7b45d0852e082103041b7a5d1331470074223314273275c4cd8d09ef6174c14b270ede7f501e6280e935814535783a8d4050d9e21a8918b1ab81f444870  heroku-nodejs-plugin-node-9-v4.tar.gz
+eefbf22a508e0fd4dea303a7d247a4c6ebb60803c5221e43dd6a9921332ad32791f6b4e95a3379c519290a6767a1dc797f3e68ed583427a53695f47c7b80ccdd  heroku-nodejs-plugin-node-9-v5.tar.gz

plugin/version

-v4
+v5

spec/ci/node_12_metrics_spec.rb

+require_relative '../spec_helper'
+
+describe "Node Metrics for v12.x" do
+  context "test metrics for Node v12.x app" do
+    let(:app) {
+      Hatchet::Runner.new(
+        "spec/fixtures/repos/node-12-metrics",
+        config: {
+          "HEROKU_METRICS_URL" => "http://localhost:3000",
+          "METRICS_INTERVAL_OVERRIDE" => "10000"
+        }
+      )
+    }
+
+    it "should deploy" do
+      app.deploy do |app|
+        data = successful_json_body(app)
+        expect(data["gauges"]["node.eventloop.delay.ms.max"]).to be >= 2000
+        expect(data["counters"]["node.gc.collections"]).to be >= 0
+        expect(data["counters"]["node.gc.young.collections"]).to be >= 0
+        expect(data["counters"]["node.gc.old.collections"]).to be >= 0
+      end
+    end
+  end
+end

spec/ci/node_12_spec.rb

+require_relative '../spec_helper'
+
+describe "Hello World for Node v12.x" do
+  context "a single-process Node v12.x app" do
+    let(:app) {
+      Hatchet::Runner.new("spec/fixtures/repos/node-12")
+    }
+
+    it "should deploy successfully" do
+      app.deploy do |app|
+        expect(successful_body(app).strip).to eq("Hello, world!")
+      end
+    end
+
+  end
+end

spec/fixtures/repos/node-12-metrics/Procfile

+web: node src/index.js

spec/fixtures/repos/node-12-metrics/package.json

+{
+  "name": "node-metrics-test-app",
+  "version": "1.0.0",
+  "engines": {
+    "node": "12.x"
+  },
+  "main": "index.js",
+  "license": "MIT",
+  "devDependencies": {},
+  "dependencies": {}
+}

spec/fixtures/repos/node-12-metrics/src/index.js

+#!/usr/bin/env node
+
+const http = require('http');
+const EventEmitter = require('events');
+
+const PORT = process.env.PORT || 5000;
+const Events = new EventEmitter();
+
+// This will block the event loop for ~lengths of time
+function blockCpuFor(ms) {
+  return new Promise((resolve, reject) => {
+    setTimeout(() => {
+      console.log(`blocking the event loop for ${ms}ms`);
+      let now = new Date().getTime();
+      let result = 0
+      while(true) {
+        result += Math.random() * Math.random();
+        if (new Date().getTime() > now + ms)
+          break;
+      }
+      resolve();
+    }, 100);
+  });
+}
+
+function getNextMetricsEvent() {
+  return new Promise((resolve, reject) => Events.once('metrics', resolve));
+}
+
+const server = http.createServer((req, res) => {
+  // wait for the next metrics event
+  getNextMetricsEvent()
+    .then(blockCpuFor(2000))
+    .then(blockCpuFor(100))
+    .then(blockCpuFor(100))
+    .then(blockCpuFor(100))
+    .then(blockCpuFor(100))
+    .then(blockCpuFor(100))
+    .then(blockCpuFor(100))
+    .then(blockCpuFor(100))
+    .then(blockCpuFor(100))
+    .then(blockCpuFor(100))
+    .then(blockCpuFor(100))
+    // gather the next metrics data which should include these pauses
+    .then(getNextMetricsEvent())
+    .then(data => {
+      res.setHeader('Content-Type', 'application/json');
+      res.end(data); 
+    })
+    .catch(() => {
+      res.statusCode = 500;
+      res.end("Something went wrong"); 
+    });
+});
+
+server.listen(PORT, () => console.log(`Listening on ${PORT}`));
+
+// Create a second server that intercepts the HTTP requests
+// sent by the metrics plugin
+const metricsListener = http.createServer((req, res) => {
+  if (req.method == 'POST') {
+    let body = '';
+    req.on('data', (data) => body += data);
+    req.on('end', () => Events.emit('metrics', body));
+    res.statusCode = 200;
+    res.end();
+  }
+});
+
+metricsListener.listen(3000, () => console.log('Listening for metrics on 3000'));
+

spec/fixtures/repos/node-12/Procfile

+web: node src/index.js

spec/fixtures/repos/node-12/app.json

+{
+  "name": "hello-world"
+}

spec/fixtures/repos/node-12/package.json

+{
+  "name": "hello-world",
+  "version": "1.0.0",
+  "engines": {
+    "node": "12.x"
+  },
+  "scripts": {
+    "prettify": "prettier --single-quote --trailing-comma all --write 'bin/*' 'src/**/*.js'",
+    "test": "jest --silent",
+    "dev": "nodemon --watch . --watch src/* src/index.js",
+    "heroku-postbuild": "echo NODE_OPTIONS: $NODE_OPTIONS"
+  },
+  "main": "index.js",
+  "license": "MIT",
+  "devDependencies": {
+    "jest": "^19.0.2",
+    "nodemon": "^1.11.0",
+    "prettier": "^0.22.0"
+  },
+  "dependencies": {}
+}

spec/fixtures/repos/node-12/src/index.js

+#!/usr/bin/env node
+
+const http = require('http');
+const crypto = require('crypto');
+
+const PORT = process.env.PORT || 5000;
+
+// This will block the event loop for ~lengths of time
+function blockCpuFor(ms) {
+	var now = new Date().getTime();
+	var result = 0
+	while(true) {
+		result += Math.random() * Math.random();
+		if (new Date().getTime() > now +ms)
+			return;
+	}
+}
+
+// block the event loop for 100ms every second
+setInterval(() => {
+  blockCpuFor(100);
+}, 1000)
+
+// block the event loop for 1sec every 30 seconds
+setInterval(() => {
+  blockCpuFor(1000);
+}, 30000)
+
+// Allocate and erase memory on an interval
+let store = [];
+
+setInterval(() => {
+  store.push(crypto.randomBytes(1000000).toString('hex'));
+}, 500);
+
+setInterval(() => {
+  store = [];
+}, 60000);
+
+const server = http.createServer((req, res) => {
+  res.statusCode = 200;
+  res.setHeader('Content-Type', 'text/plain');
+  res.end("Hello, world!");
+})
+
+server.listen(PORT, () => console.log(`Listening on ${PORT}`));

test/fixtures/build-script-override/package.json

@@ -7,7 +7,7 @@
     "url": "http://github.com/example/example.git"
   },
   "engines": {
-    "node": "~0.10.0"
+    "node": "10.x"
   },
   "scripts" : {
     "build": "echo build hook message",

test/fixtures/build-script-opt-in/package.json → test/fixtures/build-script-yarn/package.json

@@ -6,11 +6,8 @@
     "type" : "git",
     "url" : "http://github.com/example/example.git"
   },
-  "engines": {
-    "node": "10.x"
-  },
   "scripts" : {
     "build" : "echo build hook message"
   },
-  "heroku-run-build-script": true
+  "license": "MIT"
 }

test/fixtures/build-script-yarn/yarn.lock

+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+

test/fixtures/build-script/package.json

@@ -7,7 +7,7 @@
     "url" : "http://github.com/example/example.git"
   },
   "engines": {
-    "node": "~0.10.0"
+    "node": "10.x"
   },
   "scripts" : {
     "build" : "echo build hook message"

test/fixtures/empty-heroku-postbuild-yarn/README.md

+A fake README, to keep npm from polluting stderr.
\ No newline at end of file

test/fixtures/empty-heroku-postbuild-yarn/package.json

+{
+  "name": "node-buildpack-test-app",
+  "version": "0.0.1",
+  "description": "node buildpack integration test app",
+  "repository" : {
+    "type" : "git",
+    "url" : "http://github.com/example/example.git"
+  },
+  "scripts" : {
+    "build" : "echo build hook message",
+    "heroku-postbuild": ""
+  }
+}

test/fixtures/empty-heroku-postbuild-yarn/yarn.lock

+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+
+

test/fixtures/empty-heroku-postbuild/README.md

+A fake README, to keep npm from polluting stderr.
\ No newline at end of file

test/fixtures/empty-heroku-postbuild/package.json

+{
+  "name": "node-buildpack-test-app",
+  "version": "0.0.1",
+  "description": "node buildpack integration test app",
+  "repository" : {
+    "type" : "git",
+    "url" : "http://github.com/example/example.git"
+  },
+  "engines": {
+    "node": "10.x"
+  },
+  "scripts" : {
+    "build" : "echo build hook message",
+    "heroku-postbuild": ""
+  }
+}

test/fixtures/failing-build/package.json

@@ -10,9 +10,9 @@
     "hashish": "*"
   },
   "engines": {
-    "node": "0.10.38"
+    "node": "8.x"
   },
   "scripts": {
-    "postinstall": "exit 1"
+    "heroku-postbuild": "exit 1"
   }
 }

test/fixtures/has-script-fixtures/package.json

+{
+  "name": "node-buildpack-test-app",
+  "version": "0.0.1",
+  "description": "node buildpack integration test app",
+  "repository": {
+    "type": "git",
+    "url": "http://github.com/example/example.git"
+  },
+  "engines": {
+    "node": "10.x"
+  },
+  "scripts": {
+    "build": "echo build hook message",
+    "heroku-postbuild": "",
+    "random-script-name": ""
+  }
+}

test/fixtures/pre-post-build-scripts/package.json

@@ -7,7 +7,7 @@
     "url" : "http://github.com/example/example.git"
   },
   "engines": {
-    "node": "~0.10.0"
+    "node": "10.x"
   },
   "scripts" : {
     "heroku-prebuild" : "echo heroku-prebuild hook message",

test/run

@@ -16,27 +16,38 @@ testFlatmapStream() {
 }
 
 testBuildScriptBehavior() {
-  # opt in to new build script behavior
-  cache=$(mktmpdir)
-  env_dir=$(mktmpdir)
-  echo "true" > $env_dir/NEW_BUILD_SCRIPT_BEHAVIOR
-
   # The 'build' script is run by default
-  compile "build-script" $cache $env_dir
+  compile "build-script"
   assertCaptured "Running build"
   assertCapturedSuccess
 
   # the 'heroku-postbuild' script takes precedence over the 'build' script
-  compile "build-script-override" $cache $env_dir
-  assertCaptured "Detected both 'build' and 'heroku-postbuild' scripts"
+  compile "build-script-override"
+  assertCaptured "Detected both \"build\" and \"heroku-postbuild\" scripts"
   assertCaptured "Running heroku-postbuild"
   assertCapturedSuccess
 }
 
-testBuildScriptOptIn() {
-  compile "build-script-opt-in"
-  assertCaptured "Running build"
-  assertCaptured "Opting in to new default build script behavior"
+testBuildScriptYarn() {
+  compile "build-script-yarn"
+  assertCaptured "Running build (yarn)"
+  assertCaptured "build hook message"
+  assertCapturedSuccess
+}
+
+testPreferEmptyHerokuPostbuildOverBuild() {
+  compile "empty-heroku-postbuild"
+  assertCaptured "Detected both \"build\" and \"heroku-postbuild\" scripts"
+  assertCaptured "Running heroku-postbuild"
+  assertNotCaptured "build hook message"
+  assertCapturedSuccess
+}
+
+testEmptyHerokuPostbuildWithYarn() {
+  compile "empty-heroku-postbuild-yarn"
+  assertCaptured "Running heroku-postbuild (yarn)"
+  assertNotCaptured "build hook message"
+  assertNotCaptured "Script must exist"
   assertCapturedSuccess
 }
 
@@ -479,13 +490,6 @@ testInvalidNodeSemver() {
   assertCapturedError
 }
 
-testInvalidIo() {
-  compile "invalid-io"
-  assertCaptured "Resolving iojs version 2.0.99"
-  assertCaptured "Could not find Iojs version corresponding to version requirement: 2.0.99"
-  assertCapturedError
-}
-
 testSignatureInvalidation() {
   cache=$(mktmpdir)
   env_dir=$(mktmpdir)
@@ -527,10 +531,8 @@ testDetectWithoutPackageJson() {
 
 testIoJs() {
   compile "iojs"
-  assertCaptured "engines.iojs (package.json):  1.0."
-  assertCaptured "Downloading and installing iojs 1.0."
-  assertNotCaptured "Downloading and installing npm"
-  assertCapturedSuccess
+  assertCaptured "io.js no longer supported"
+  assertCapturedError
 }
 
 testSpecificVersion() {
@@ -562,11 +564,6 @@ testOldNpm() {
   assertCapturedError
 }
 
-testOldNpm2() {
-  compile "failing-build"
-  assertCaptured "This version of npm (1.4.28) has several known issues"
-}
-
 testNonexistentNpm() {
   compile "nonexistent-npm"
   assertCaptured "Unable to install npm 1.1.65"
@@ -594,7 +591,6 @@ testNpmVersionSpecific() {
 
 testFailingBuild() {
   compile "failing-build"
-  assertCaptured "Building dependencies"
   assertCaptured "Build failed"
   assertCaptured "We're sorry this build is failing"
   assertNotCaptured "Checking startup method"
@@ -874,6 +870,12 @@ testCIEnvVars() {
   assertCapturedSuccess
 }
 
+# If compile fails, test-compile should also fail
+testCICompileFails() {
+  testCompile "failing-build"
+  assertCapturedError
+}
+
 testCIEnvVarsOverride() {
   env_dir=$(mktmpdir)
   echo "banana" > $env_dir/NODE_ENV
@@ -1031,6 +1033,96 @@ testMemoryMetrics() {
   assertFileNotContains "measure#buildpack.nodejs.exec.heroku-postbuild.memory=" $metrics_log
 }
 
+testBuildMetaData() {
+  local log_file=$(mktemp)
+
+  BUILDPACK_LOG_FILE="$log_file" compile "pre-post-build-scripts"
+
+  # build info
+  assertFileContains "node-package-manager=npm" $log_file
+  assertFileContains "checked-in-node-modules=false" $log_file
+  assertFileContains "has-node-lock-file=false" $log_file
+  assertFileContains "cache-status=not-found" $log_file
+  assertFileContains "node-build-success=true" $log_file
+  assertFileContains "build-time=" $log_file
+  assertFileContains "app-uuid=" $log_file
+  assertFileContains "build-uuid=" $log_file
+
+  # binary versions
+  assertFileContains "node-version-request=10.x" $log_file
+  assertFileContains "npm-version-request= " $log_file
+
+  # log build scripts
+  assertFileContains "heroku-prebuild-script=\"echo heroku-prebuild hook message\"" $log_file
+  assertFileContains "heroku-postbuild-script=\"echo heroku-postbuild hook message\"" $log_file
+  assertFileContains "build-script= " $log_file
+
+  # monitor calls
+  assertFileContains "install-node-binary-memory=" $log_file
+  assertFileContains "install-node-binary-time=" $log_file
+  assertFileContains "install-npm-binary-time=" $log_file
+  assertFileContains "install-npm-binary-memory=" $log_file
+  assertFileContains "heroku-prebuild-time=" $log_file
+  assertFileContains "heroku-prebuild-memory=" $log_file
+  assertFileContains "npm-install-time=" $log_file
+  assertFileContains "npm-install-memory=" $log_file
+  assertFileContains "heroku-postbuild-time=" $log_file
+  assertFileContains "heroku-postbuild-memory=" $log_file
+  assertFileContains "npm-prune-memory=" $log_file
+  assertFileContains "npm-prune-time=" $log_file
+
+  # erase the log file
+  echo "" > $log_file
+  BUILDPACK_LOG_FILE="$log_file" compile "yarn"
+
+  assertFileContains "node-package-manager=yarn" $log_file
+  assertFileContains "has-node-lock-file=true" $log_file
+  assertFileContains "yarn-version-request=1.x" $log_file
+  assertFileContains "yarn-version=1." $log_file
+  assertFileContains "install-yarn-binary-memory=" $log_file
+  assertFileContains "install-yarn-binary-time=" $log_file
+  assertFileContains "node-build-success=true" $log_file
+
+  # log resolve logic dark-launch
+  assertFileContains "resolve-matches-nodebin-yarn=true" $log_file
+  assertFileContains "resolve-matches-nodebin-node=true" $log_file
+}
+
+testFailingBuildMetaData() {
+  local log_file=$(mktemp)
+
+  BUILDPACK_LOG_FILE="$log_file" compile "bad-json"
+  assertFileContains "failure=invalid-package-json" $log_file
+  assertCapturedError
+
+  echo "" > $log_file
+  BUILDPACK_LOG_FILE="$log_file" compile "yarn-lockfile-out-of-date"
+  assertFileContains "failure=outdated-yarn-lockfile" $log_file
+  assertCapturedError
+}
+
+testPropagateAppUUID() {
+  env_dir=$(mktmpdir)
+  local log_file=$(mktemp)
+  local cache_dir=${2:-$(mktmpdir)}
+  echo "$log_file" > $env_dir/BUILDPACK_LOG_FILE
+
+  # save the generated app-uuid for the first build
+  compile "node-10" $cache_dir $env_dir
+  assertFileContains "app-uuid=" $log_file
+  local uuid=$(cat $log_file | sed -n -e 's/^.*app-uuid=\([^ ]*\).*/\1/p')
+
+  # create a new log file
+  log_file=$(mktemp)
+  echo "$log_file" > $env_dir/BUILDPACK_LOG_FILE
+
+  # recompile with the same cache directory
+  compile "node-10" $cache_dir $env_dir
+  assertFileContains "app-uuid" $log_file
+  # make sure that the app-uuid is the same
+  assertEquals "$uuid" "$(cat $log_file | sed -n -e 's/^.*app-uuid=\([^ ]*\).*/\1/p')"
+}
+
 testBinDetectWarnings() {
   detect "slugignore-package-json"
   assertCapturedError "'package.json' listed in '.slugignore' file"
@@ -1093,6 +1185,15 @@ compile() {
   capture ${bp_dir}/bin/compile ${compile_dir} ${2:-$(mktmpdir)} $3
 }
 
+testCompile() {
+  default_process_types_cleanup
+  bp_dir=$(mktmpdir)
+  compile_dir=$(mktmpdir)
+  cp -a "$(pwd)"/* ${bp_dir}
+  cp -a ${bp_dir}/test/fixtures/$1/. ${compile_dir}
+  capture ${bp_dir}/bin/test-compile ${compile_dir} ${2:-$(mktmpdir)} $3
+}
+
 # This is meant to be run after `compile`. `cleanupStartup` must be run
 # after this function is called before other tests are executed
 executeStartup() {

test/unit

@@ -108,6 +108,26 @@ testKeyValue() {
   assertEquals "" "$(kv_list $store)"
 }
 
+testKeyValueNoNewLine() {
+  local store
+
+  # use a fixture that does not have an empty line after the final entry
+  store="$(pwd)/test/unit-fixtures/kvstore/no-new-line"
+
+  assertEquals "$(printf "%s\n" a=b b=c)" "$(kv_list $store)"
+  assertEquals "$(printf "%s\n" a b)" "$(kv_keys $store)" 
+}
+
+testKeyValueEmptyLine() {
+  local store
+
+  # use a fixture that has an extra empty line
+  store="$(pwd)/test/unit-fixtures/kvstore/empty-line"
+
+  assertEquals "$(printf "%s\n" a=b b=c)" "$(kv_list $store)"
+  assertEquals "$(printf "%s\n" a b)" "$(kv_keys $store)" 
+}
+
 testKeyValueEscaping() {
   local store=$(mktemp)
 
@@ -151,21 +171,71 @@ testKeyValueNoFile() {
 testBuildData() {
   local cache_dir=$(mktemp -d)
 
-  bd_create $cache_dir
+  meta_create $cache_dir
 
-  bd_set "test" "foo"
-  assertEquals "test=foo" "$(log_build_data)"
+  meta_set "test" "foo"
+  assertEquals "test=foo" "$(log_meta_data)"
 
-  bd_set "test" "different-foo"
-  assertEquals "test=different-foo" "$(log_build_data)"
+  meta_set "test" "different-foo"
+  assertEquals "test=different-foo" "$(log_meta_data)"
 
-  bd_set "foo" "value with spaces"
-  assertEquals "foo=\"value with spaces\" test=different-foo" "$(log_build_data)"
+  meta_set "foo" "value with spaces"
+  assertEquals "foo=\"value with spaces\" test=different-foo" "$(log_meta_data)"
 
   # values are printed with the keys sorted alphabetically
   # this isn't required, and this test serves as documentation
-  bd_set "a" "this should come first"
-  assertEquals "a=\"this should come first\" foo=\"value with spaces\" test=different-foo" "$(log_build_data)"
+  meta_set "a" "this should come first"
+  assertEquals "a=\"this should come first\" foo=\"value with spaces\" test=different-foo" "$(log_meta_data)"
+
+  # dates generated by running `nowms; sleep 10; nowms`
+  meta_time "time" "1545178120033" "1545178130043"
+  assertEquals "10.010" "$(meta_get time)"
+
+  # dates generated by running `nowms; sleep 1; nowms`
+  meta_time "time" "1545178503025" "1545178504027"
+  assertEquals "1.002" "$(meta_get time)"
+
+  # dates generated by running `nowms; sleep 30; nowms`
+  meta_time "time" "1545178521204" "1545178551206"
+  assertEquals "30.002" "$(meta_get time)"
+}
+
+testBuildDataPreviousBuild() {
+  local cache_dir=$(mktemp -d)
+
+  # the first time, there will be no previous build file
+  meta_create "$cache_dir"
+  assertContains "nodejs" "$BUILD_DATA_FILE"
+  assertContains "nodejs-prev" "$PREVIOUS_BUILD_DATA_FILE"
+  assertFileExists "$BUILD_DATA_FILE"
+
+  # set a value in the build data file
+  meta_set "test" "foo"
+  assertFileContains "test=foo" "$BUILD_DATA_FILE"
+  assertFileDoesNotExist "$PREVIOUS_BUILD_DATA_FILE"
+
+  assertEquals "$(meta_get test)" "foo"
+  assertEquals "$(meta_prev_get test)" ""
+
+  # the second time this is called (cache restored)
+  # there will be a previous build file
+  meta_create "$cache_dir"
+  assertFileExists "$BUILD_DATA_FILE"
+  assertFileExists "$PREVIOUS_BUILD_DATA_FILE"
+
+  # the data stored in the previous build should now be in the second file
+  assertFileNotContains "test=foo" "$BUILD_DATA_FILE"
+  assertFileContains "test=foo" "$PREVIOUS_BUILD_DATA_FILE"
+  assertEquals "$(meta_get test)" ""
+  assertEquals "$(meta_prev_get test)" "foo"
+  meta_set "test" "bar"
+
+  # doing it once more does not result in an error
+  meta_create "$cache_dir"
+  assertFileExists "$BUILD_DATA_FILE"
+  assertFileExists "$PREVIOUS_BUILD_DATA_FILE" 
+  assertEquals "$(meta_prev_get test)" "bar"
+  assertEquals "$(meta_get test)" ""
 }
 
 testWebConcurrencyProfileScript() {
@@ -210,15 +280,103 @@ testWebConcurrencyProfileScript() {
   assertEquals "1" "$(calculate_concurrency 512 1)"
 }
 
+isUUID() {
+  if [[ ${1//-/} =~ ^[[:xdigit:]]{32}$ ]]; then
+    echo true
+  else
+    echo false
+  fi
+}
+
+testUUID() {
+  local first second
+  first=$(uuid)
+  second=$(uuid)
+
+  assertNotEquals "$first" "$second"
+  assertEquals "true" "$(isUUID "$first")"
+  assertEquals "true" "$(isUUID "$second")"
+}
+
+testUUIDFallback() {
+  local first second
+  first=$(uuid_fallback)
+  second=$(uuid_fallback)
+
+  assertNotEquals "$first" "$second"
+  assertEquals "true" "$(isUUID "$first")"
+  assertEquals "true" "$(isUUID "$second")"
+}
+
+testHasScript() {
+  local file="$(pwd)/test/fixtures/has-script-fixtures/package.json"
+  assertEquals "true" "$(has_script "$file" "build")"
+  assertEquals "true" "$(has_script "$file" "heroku-postbuild")"
+  assertEquals "false" "$(has_script "$file" "postinstall")"
+  assertEquals "true" "$(has_script "$file" "random-script-name")"
+}
+
+testExperiments() {
+  local schema="$(pwd)/test/unit-fixtures/experiments/experiments-v1"
+  local schema_next="$(pwd)/test/unit-fixtures/experiments/experiments-v1-next"
+  local schema_v2="$(pwd)/test/unit-fixtures/experiments/experiments-v2"
+  local cache_dir=$(mktemp -d)
+  local val
+
+  experiments_init "nodejs" "$cache_dir" "$schema"
+
+  # these should always be the same
+  assertEquals "true" "$(experiments_get "all-on")"
+  assertEquals "false" "$(experiments_get "all-off")"
+  # this will change, but stay the same between runs
+  val="$(experiments_get "ab-test")"
+
+  # pretend this is the next time this build is run
+  experiments_init "nodejs" "$cache_dir" "$schema"
+
+  # these should always be the same
+  assertEquals "true" "$(experiments_get "all-on")"
+  assertEquals "false" "$(experiments_get "all-off")"
+  # val should be the same as it was before
+  assertEquals "$val" "$(experiments_get "ab-test")"
+
+  # now we add a new feature to the schema
+  experiments_init "nodejs" "$cache_dir" "$schema_next"
+
+  assertEquals "true" "$(experiments_get "all-on")"
+  assertEquals "false" "$(experiments_get "all-off")"
+  assertEquals "$val" "$(experiments_get "ab-test")"
+  assertEquals "true" "$(experiments_get "new-always-on")"
+
+  # reset the schema
+  experiments_init "nodejs" "$cache_dir" "$schema_v2"
+  assertNotNull "$(experiments_get "new-feature")"
+  assertNull "$(experiments_get "all-on")"
+  assertNull "$(experiments_get "all-off")"
+  assertNull "$(experiments_get "ab-test")"
+  assertNull "$(experiments_get "new-always-on")"
+}
+
+BP_DIR="$(pwd)"
+
 # mocks
 source "$(pwd)"/test/mocks/stdlib.sh
 
 # the modules to be tested
+
+source "$(pwd)"/lib/uuid.sh
+source "$(pwd)"/lib/environment.sh
+source "$(pwd)"/lib/json.sh
+source "$(pwd)"/lib/json.sh
 source "$(pwd)"/lib/monitor.sh
 source "$(pwd)"/lib/output.sh
 source "$(pwd)"/lib/kvstore.sh
-source "$(pwd)"/lib/build-data.sh
+source "$(pwd)"/lib/experiments.sh
+source "$(pwd)"/lib/metadata.sh
 source "$(pwd)"/profile/WEB_CONCURRENCY.sh
 
+# testing utils
+source "$(pwd)"/test/utils
+
 # import the testing framework
 source "$(pwd)"/test/shunit2

test/unit-fixtures/experiments/experiments-v1

+#version=1
+ab-test=50
+all-on=100
+all-off=0

test/unit-fixtures/experiments/experiments-v1-next

+#version=1
+ab-test=50
+all-on=100
+all-off=0
+new-always-on=100

test/unit-fixtures/experiments/experiments-v2

+#version=2
+new-feature=50

test/unit-fixtures/kvstore/empty-line

+
+a=b
+b=c

test/unit-fixtures/kvstore/no-new-line

+a=b
+b=c
\ No newline at end of file