test and implementation for missing devDependencies

bin/compile

@@ -42,6 +42,7 @@ handle_failure() {
   header "Build failed"
   warn_untracked_dependencies "$LOG_FILE"
   warn_angular_resolution "$LOG_FILE"
+  warn_missing_devdeps "$LOG_FILE"
   failure_message | output "$LOG_FILE"
 }
 trap 'handle_failure' ERR

lib/failure.sh

@@ -87,3 +87,17 @@ warn_angular_resolution() {
     warning "Bower may need a resolution hint for angular" "https://github.com/bower/bower/issues/1746"
   fi
 }
+
+warn_missing_devdeps() {
+  local log_file="$1"
+  if grep -qi 'cannot find module' "$log_file"; then
+    warning "A module may be missing from package.json" "https://devcenter.heroku.com/articles/troubleshooting-node-deploys#ensure-you-aren-t-relying-on-untracked-dependencies"
+    if [ "$NPM_CONFIG_PRODUCTION" == "true" ]; then
+      local devDeps=$(read_json "$BUILD_DIR/package.json" ".devDependencies")
+      echo "devDependencies: $devDeps"
+      if [ "$devDeps" != "" ]; then
+        warning "A module may be specified in devDependencies instead of dependencies" "https://devcenter.heroku.com/articles/nodejs-support#devdependencies"
+      fi
+    fi
+  fi
+}

test/fixtures/missing-devdeps-1/package.json

+{
+  "name": "missing-devdeps-1",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "postinstall": "node postinstall.js"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC"
+}

test/fixtures/missing-devdeps-1/postinstall.js

+const lodash = require('lodash');

test/fixtures/missing-devdeps-2/package.json

+{
+  "name": "missing-devdeps-1",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "postinstall": "node postinstall.js"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "devDependencies": {
+    "lodash": "4.13.1"
+  }
+}

test/fixtures/missing-devdeps-2/postinstall.js

+const lodash = require('lodash');

test/run

 #!/usr/bin/env bash
 # See README.md for info on running these tests.
 
+testWarnDevDeps() {
+  compile "missing-devdeps-1"
+  assertCaptured "A module may be missing"
+  assertNotCaptured "A module may be specified"
+  assertCapturedError
+  compile "missing-devdeps-2"
+  assertCaptured "A module may be missing"
+  assertCaptured "A module may be specified"
+  assertCapturedError
+  compile "failing-build"
+  assertNotCaptured "A module may be missing"
+  assertNotCaptured "A module may be specified"
+  assertCapturedError
+}
+
 testEnvBlacklist() {
   local cache=$(mktmpdir)
   local env_dir=$(mktmpdir)