fix: checkIsGCE: report unexpected errors (#164)

ts/lib/auth/googleauth.ts

@@ -209,11 +209,15 @@ export class GoogleAuth {
       }
 
       // Determine if we're running on GCE.
-      this._checkIsGCE((gce) => {
+      this._checkIsGCE((err, gce) => {
         if (gce) {
           // For GCE, just return a default ComputeClient. It will take care of
           // the rest.
           my_callback(null, new this.ComputeClient());
+        } else if (err) {
+          my_callback(new Error(
+              'Unexpected error while acquiring application default ' +
+              'credentials: ' + err.message));
         } else {
           // We failed to find the default credentials. Bail out with an error.
           my_callback(new Error(
@@ -230,20 +234,30 @@ export class GoogleAuth {
    * @param {function=} callback The callback.
    * @api private
    */
-  public _checkIsGCE(callback: (isGCE: boolean) => void) {
+  public _checkIsGCE(callback: (err: Error, isGCE?: boolean) => void) {
     if (this._isGCE !== undefined) {
-      callback(this._isGCE);
+      setImmediate(() => {
+        callback(null, this._isGCE);
+      });
     } else {
       if (!this.transporter) {
         this.transporter = new DefaultTransporter();
       }
       this.transporter.request(
           {method: 'GET', uri: 'http://metadata.google.internal', json: true},
-          (err, body, res) => {
-            if (!err && res && res.headers) {
-              this._isGCE = res.headers['metadata-flavor'] === 'Google';
+          (err: any, body, res) => {
+            if (err) {
+              if (err.code !== 'ENOTFOUND') {
+                // Unexpected error occurred. TODO(ofrobots): retry if this was
+                // a transient error.
+                return callback(err);
+              }
+              this._isGCE = false;
+              return callback(null, this._isGCE);
             }
-            callback(this._isGCE);
+            this._isGCE = res && res.headers &&
+                res.headers['metadata-flavor'] === 'Google';
+            callback(null, this._isGCE);
           });
     }
   }

ts/test/test.googleauth.ts

@@ -95,9 +95,9 @@ function returns(value: any) {
   };
 }
 
-function callsBack(value: any) {
+function callsBack(err: any, value: any) {
   return (callback: Function) => {
-    callback(value);
+    callback(err, value);
   };
 }
 
@@ -966,7 +966,7 @@ describe('GoogleAuth', () => {
                creds, 'GCLOUD_PROJECT', projectId);
 
            creds._fileExists = returns(false);
-           creds._checkIsGCE = callsBack(false);
+           creds._checkIsGCE = callsBack(null, false);
          };
 
          // Set up a new GoogleAuth and prepare it for local environment
@@ -1126,7 +1126,7 @@ describe('GoogleAuth', () => {
                './ts/test/fixtures/private.json');
 
            creds._fileExists = returns(false);
-           creds._checkIsGCE = callsBack(false);
+           creds._checkIsGCE = callsBack(null, false);
          };
 
          // Set up a new GoogleAuth and prepare it for local environment
@@ -1205,7 +1205,7 @@ describe('GoogleAuth', () => {
       auth._pathJoin = pathJoin;
       auth._osPlatform = returns('win32');
       auth._fileExists = returns(true);
-      auth._checkIsGCE = callsBack(true);
+      auth._checkIsGCE = callsBack(null, true);
       insertWellKnownFilePathIntoAuth(
           auth, 'foo:gcloud:application_default_credentials.json',
           './ts/test/fixtures/private2.json');
@@ -1239,7 +1239,7 @@ describe('GoogleAuth', () => {
          auth._pathJoin = pathJoin;
          auth._osPlatform = returns('win32');
          auth._fileExists = returns(true);
-         auth._checkIsGCE = callsBack(true);
+         auth._checkIsGCE = callsBack(null, true);
          insertWellKnownFilePathIntoAuth(
              auth, 'foo:gcloud:application_default_credentials.json',
              './ts/test/fixtures/private2.json');
@@ -1268,7 +1268,7 @@ describe('GoogleAuth', () => {
          auth._pathJoin = pathJoin;
          auth._osPlatform = returns('win32');
          auth._fileExists = returns(false);
-         auth._checkIsGCE = callsBack(true);
+         auth._checkIsGCE = callsBack(null, true);
 
          // Execute.
          auth.getApplicationDefault((err, result) => {
@@ -1282,6 +1282,27 @@ describe('GoogleAuth', () => {
          });
        });
 
+    it('should report GCE error when checking for GCE fails', (done) => {
+      // Set up the creds.
+      // * Environment variable is not set.
+      // * Well-known file is not set.
+      // * Running on GCE is set to true.
+      const auth = new GoogleAuth();
+      blockGoogleApplicationCredentialEnvironmentVariable(auth);
+      insertEnvironmentVariableIntoAuth(auth, 'APPDATA', 'foo');
+      auth._pathJoin = pathJoin;
+      auth._osPlatform = returns('win32');
+      auth._fileExists = returns(false);
+      auth._checkIsGCE = callsBack(new Error('fake error'), undefined);
+
+      // Execute.
+      auth.getApplicationDefault((err, result) => {
+        assert(err instanceof Error);
+        assert.equal(result, undefined);
+        done();
+      });
+    });
+
     it('should also get project ID', (done) => {
       // We expect private.json to be the file that is used.
       const fileContents =
@@ -1302,7 +1323,7 @@ describe('GoogleAuth', () => {
       auth._pathJoin = pathJoin;
       auth._osPlatform = returns('win32');
       auth._fileExists = returns(true);
-      auth._checkIsGCE = callsBack(true);
+      auth._checkIsGCE = callsBack(null, true);
       insertWellKnownFilePathIntoAuth(
           auth, 'foo:gcloud:application_default_credentials.json',
           './ts/test/fixtures/private2.json');