Merge pull request #169 from heroku/skip-replace-same-npm

test and implementation for skipping replacement of npm

bin/compile

@@ -110,8 +110,12 @@ if [ "$npm_engine" != "" ]; then
     info "Resolving npm version ${npm_engine} via semver.io..."
     npm_engine=$(curl --silent --get --data-urlencode "range=${npm_engine}" https://semver.herokuapp.com/npm/resolve)
   fi
-  info "Downloading and installing npm $npm_engine (replacing version `npm --version`)..."
-  npm install --quiet -g npm@$npm_engine > /dev/null 2>&1 | indent
+  if [[ `npm --version` == "$npm_engine" ]]; then
+    info "Version `npm --version` already installed"
+  else
+    info "Downloading and installing npm $npm_engine (replacing version `npm --version`)..."
+    npm install --quiet -g npm@$npm_engine > /dev/null 2>&1 | indent
+  fi
 fi
 
 # Run subsequent commands from the build directory

bin/test

@@ -54,6 +54,12 @@ testOldNpm() {
   assertCapturedSuccess
 }
 
+testSameNpm() {
+  compile "same-npm"
+  assertCaptured "Version 1.4.28 already installed"
+  assertCapturedSuccess
+}
+
 testFailingBuild() {
   compile "failing-build"
   assertCaptured "Build failed"

test/npm-version-range/package.json

@@ -7,7 +7,7 @@
     "url" : "http://github.com/example/example.git"
   },
   "engines": {
-    "node": "0.10.33",
+    "node": "0.10.12",
     "npm": "1.4.x"
   }
 }

test/same-npm/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": "0.10.33",
+    "npm": "1.4.28"
+  },
+  "scripts": {
+    "start": "node server.js"
+  }
+}