common: add getProjectId()

packages/common/src/service.js

@@ -29,6 +29,8 @@ var extend = require('extend');
  */
 var util = require('./util.js');
 
+var PROJECT_ID_TOKEN = '{{projectId}}';
+
 /**
  * Service is a base class, meant to be inherited from by a "service," like
  * BigQuery or Storage.
@@ -57,11 +59,33 @@ function Service(config, options) {
   this.globalInterceptors = arrify(options.interceptors_);
   this.interceptors = [];
   this.packageJson = config.packageJson;
-  this.projectId = options.projectId || '{{projectId}}';
+  this.projectId = options.projectId || PROJECT_ID_TOKEN;
   this.projectIdRequired = config.projectIdRequired !== false;
   this.Promise = options.promise || Promise;
 }
 
+/**
+ * Get and update the Service's project ID.
+ *
+ * @param {function} callback - The callback function.
+ */
+Service.prototype.getProjectId = function(callback) {
+  var self = this;
+
+  this.authClient.getProjectId(function(err, projectId) {
+    if (err) {
+      callback(err);
+      return;
+    }
+
+    if (self.projectId === PROJECT_ID_TOKEN && projectId) {
+      self.projectId = projectId;
+    }
+
+    callback(null, self.projectId);
+  });
+};
+
 /**
  * Make an authenticated API request.
  *

packages/common/test/service.js

@@ -167,6 +167,51 @@ describe('Service', function() {
     });
   });
 
+  describe('getProjectId', function() {
+    it('should get the project ID from the auth client', function(done) {
+      service.authClient = {
+        getProjectId: function() {
+          done();
+        }
+      };
+
+      service.getProjectId(assert.ifError);
+    });
+
+    it('should return error from auth client', function(done) {
+      var error = new Error('Error.');
+
+      service.authClient = {
+        getProjectId: function(callback) {
+          callback(error);
+        }
+      };
+
+      service.getProjectId(function(err) {
+        assert.strictEqual(err, error);
+        done();
+      });
+    });
+
+    it('should update and return the project ID if found', function(done) {
+      var service = new Service({}, {});
+      var projectId = 'detected-project-id';
+
+      service.authClient = {
+        getProjectId: function(callback) {
+          callback(null, projectId);
+        }
+      };
+
+      service.getProjectId(function(err, projectId_) {
+        assert.ifError(err);
+        assert.strictEqual(service.projectId, projectId);
+        assert.strictEqual(projectId_, projectId);
+        done();
+      });
+    });
+  });
+
   describe('request_', function() {
     var reqOpts;