fix(createVM): do not define machineType or networkInterfaces when template provided (#530)

Fixes #529

Author: stephenplusplus

packages/google-cloud-compute/src/zone.js

@@ -582,23 +582,18 @@ class Zone extends common.ServiceObject {
   createVM(name, config, callback) {
     const self = this;
     const query = {};
-    const body = Object.assign(
-      {
-        name: name,
-        machineType: 'n1-standard-1',
-        networkInterfaces: [
-          {
-            network: 'global/networks/default',
-          },
-        ],
-      },
-      config
-    );
+    const body = Object.assign({name}, config);
     if (body.template) {
       query.sourceInstanceTemplate = body.template;
       delete body.template;
     }
-    if (body.machineType.indexOf('/') === -1) {
+    if (!is.defined(query.sourceInstanceTemplate)) {
+      body.machineType = body.machineType || 'n1-standard-1';
+      body.networkInterfaces = body.networkInterfaces || [
+        {network: 'global/networks/default'},
+      ];
+    }
+    if (body.machineType && body.machineType.indexOf('/') === -1) {
       // The specified machineType is only a partial name, e.g. 'n1-standard-1'.
       body.machineType = format('zones/{zoneName}/machineTypes/{machineType}', {
         zoneName: this.name,

packages/google-cloud-compute/test/zone.js

@@ -791,6 +791,27 @@ describe('Zone', () => {
 
         zone.createVM(NAME, CONFIG, assert.ifError);
       });
+
+      it('should not set default value for machineType', done => {
+        zone.request = function (reqOpts) {
+          assert.strictEqual(typeof reqOpts.json.machineType, 'undefined');
+          done();
+        };
+
+        zone.createVM(NAME, CONFIG, assert.ifError);
+      });
+
+      it('should not set default value for network', done => {
+        zone.request = function (reqOpts) {
+          assert.strictEqual(
+            typeof reqOpts.json.networkInterfaces,
+            'undefined'
+          );
+          done();
+        };
+
+        zone.createVM(NAME, CONFIG, assert.ifError);
+      });
     });
 
     describe('config.machineType', () => {