Increase Node memory default during builds (#561)

We've seen an increasing failures due to frontend build exceeding Node
default 1.5GB memory limit during build. Heroku runs these builds on
machines with 2.5GB of memory. This increases the default limit for
Node 8 and above by passing commands via `NODE_OPTIONS` during build
if the user has not set this manually

bin/compile

@@ -85,6 +85,7 @@ mkdir -p "$BUILD_DIR/.heroku/node/"
 cd $BUILD_DIR
 create_env # can't pipe the whole thing because piping causes subshells, preventing exports
 list_node_config | output "$LOG_FILE"
+create_build_env
 
 ### Configure package manager cache directories
 [ ! "$YARN_CACHE_FOLDER" ] && export YARN_CACHE_FOLDER=$(mktemp -d -t yarncache.XXXXX)

lib/environment.sh

@@ -22,6 +22,14 @@ create_default_env() {
   export NODE_VERBOSE=${NODE_VERBOSE:-false}
 }
 
+create_build_env() {
+  # if the user hasn't set NODE_OPTIONS, increase the default amount of space
+  # that a node process can address to match that of the build dynos (2.5GB)
+  if [[ -z $NODE_OPTIONS ]]; then
+    export NODE_OPTIONS="--max_old_space_size=2560"
+  fi
+}
+
 list_node_config() {
   echo ""
   printenv | grep ^NPM_CONFIG_ || true

test/fixtures/print-node-options/README.md

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

test/fixtures/print-node-options/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"
+  },
+  "dependencies": {
+    "hashish": "*"
+  },
+  "engines": {
+    "node": "8.x"
+  },
+  "scripts": {
+    "start": "node foo.js",
+    "heroku-postbuild": "echo NODE_OPTIONS=$NODE_OPTIONS"
+  }
+}

test/run

@@ -45,6 +45,18 @@ testNodeModulesCached() {
   assertCapturedSuccess
 }
 
+testSetBuildEnv() {
+  cache=$(mktmpdir)
+  env_dir=$(mktmpdir)
+
+  compile "print-node-options"
+  assertCaptured "NODE_OPTIONS=--max_old_space_size=2560"
+
+  echo "--max_old_space_size=1234" > $env_dir/NODE_OPTIONS
+  compile "print-node-options" $cache $env_dir
+  assertCaptured "NODE_OPTIONS=--max_old_space_size=1234"
+}
+
 testYarn() {
   compile "yarn"
   assertCaptured "installing yarn"