core: recognize GCLOUD_PROJECT env var

docs/authentication.md

@@ -17,6 +17,8 @@ A `config` object requires the following properties:
 
 1. `projectId`
 
+  If you wish, you can set an environment variable (`GCLOUD_PROJECT`) in place of specifying this inline.
+
 2. One of the following:
   1. `config.credentials` object containing `client_email` and `private_key` properties.
   2. `config.keyFilename` path to a .json, .pem, or .p12 key file.

lib/common/util.js

@@ -43,6 +43,7 @@ var util = module.exports;
 
 var missingProjectIdError = new Error([
   'Sorry, we cannot connect to Google Cloud Services without a project ID.',
+  'You may specify one with an environment variable named "GCLOUD_PROJECT".',
   'See https://googlecloudplatform.github.io/gcloud-node/#/authentication for',
   'a detailed guide on creating an authenticated connection.'
 ].join(' '));
@@ -90,7 +91,13 @@ function extendGlobalConfig(globalConfig, overrides) {
     delete options.keyFilename;
   }
 
-  return extend(true, {}, options, overrides);
+  var defaults = {};
+
+  if (process.env.GCLOUD_PROJECT) {
+    defaults.projectId = process.env.GCLOUD_PROJECT;
+  }
+
+  return extend(true, defaults, options, overrides);
 }
 
 util.extendGlobalConfig = extendGlobalConfig;

test/common/util.js

@@ -103,6 +103,8 @@ describe('common/util', function() {
   it('should export an error for module instantiation errors', function() {
     var missingProjectIdError = new Error([
       'Sorry, we cannot connect to Google Cloud Services without a project ID.',
+      'You may specify one with an environment variable named',
+      '"GCLOUD_PROJECT".',
       'See https://googlecloudplatform.github.io/gcloud-node/#/authentication',
       'for a detailed guide on creating an authenticated connection.'
     ].join(' '));
@@ -200,6 +202,26 @@ describe('common/util', function() {
       assert.deepEqual(options, { credentials: {} });
     });
 
+    it('should honor the GCLOUD_PROJECT environment variable', function() {
+      var newProjectId = 'envvar-project-id';
+      var cachedProjectId = process.env.GCLOUD_PROJECT;
+      process.env.GCLOUD_PROJECT = newProjectId;
+
+      // No projectId specified:
+      var globalConfig = { keyFilename: 'key.json' };
+      var overrides = {};
+
+      var options = util.extendGlobalConfig(globalConfig, overrides);
+
+      if (cachedProjectId) {
+        process.env.GCLOUD_PROJECT = cachedProjectId;
+      } else {
+        delete process.env.GCLOUD_PROJECT;
+      }
+
+      assert.strictEqual(options.projectId, newProjectId);
+    });
+
     it('should not modify original object', function() {
       var globalConfig = { keyFilename: 'key.json' };
       util.extendGlobalConfig(globalConfig, { credentials: {} });