Polyfill plugin JS API interface to prevent runtime exceptions

Gerrit plugins built with GWT and gerrit-plugin-gwtui access
non-documented properties and depend on installGwt method's behavior.
This change provides minimal compatible interface to avoid runtime JS
exceptions when loading such plugins into PolyGerrit.

Bug: Issue 5151
Change-Id: Idf3f341a3623f4d3ae8c2f848b0043effa2d2f2d

polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html

@@ -33,27 +33,30 @@ limitations under the License.
     var element;
     var plugin;
     var errorStub;
+    var sandbox;
+
     var throwErrFn = function() {
       throw Error('Unfortunately, this handler has stopped');
     };
 
     setup(function() {
+      sandbox = sinon.sandbox.create();
       stub('gr-rest-api-interface', {
         getAccount: function() {
           return Promise.resolve({name: 'Judy Hopps'});
         },
       });
       element = fixture('basic');
-      errorStub = sinon.stub(console, 'error');
+      errorStub = sandbox.stub(console, 'error');
       Gerrit._setPluginsCount(1);
       Gerrit.install(function(p) { plugin = p; }, '0.1',
           'http://test.com/plugins/testplugin/static/test.js');
     });
 
     teardown(function() {
+      sandbox.restore();
       element._removeEventCallbacks();
       plugin = null;
-      errorStub.restore();
     });
 
     test('url', function() {
@@ -94,7 +97,7 @@ limitations under the License.
         _number: 42,
         revisions: {def: {_number: 2}, abc: {_number: 1}},
       };
-      var spy = sinon.spy();
+      var spy = sandbox.spy();
       Gerrit._setPluginsCount(1);
       plugin.on(element.EventType.SHOW_CHANGE, spy);
       element.handleEvent(element.EventType.SHOW_CHANGE,
@@ -118,11 +121,10 @@ limitations under the License.
       element.handleEvent(element.EventType.COMMENT, {node: testCommentNode});
     });
 
-    test('revert event', function(done) {
+    test('revert event', function() {
       function appendToRevertMsg(c, revertMsg, originalMsg) {
         return revertMsg + '\n' + originalMsg.replace(/^/gm, '> ') + '\ninfo';
       }
-      done();
 
       assert.equal(element.modifyRevertMsg(null, 'test', 'origTest'), 'test');
       assert.equal(errorStub.callCount, 0);
@@ -139,19 +141,18 @@ limitations under the License.
       assert.isTrue(errorStub.calledTwice);
     });
 
-    test('postrevert event', function(done) {
+    test('postrevert event', function() {
       function getLabels(c) {
         return {'Code-Review': 1};
       }
-      done();
 
       assert.deepEqual(element.getLabelValuesPostRevert(null), {});
       assert.equal(errorStub.callCount, 0);
 
       plugin.on(element.EventType.POST_REVERT, throwErrFn);
       plugin.on(element.EventType.POST_REVERT, getLabels);
-      assert.deepEqual(element.getLabelValuesPostRevert(null),
-                       {'Code-Review': 1});
+      assert.deepEqual(
+          element.getLabelValuesPostRevert(null), {'Code-Review': 1});
       assert.isTrue(errorStub.calledOnce);
     });
 
@@ -189,7 +190,7 @@ limitations under the License.
     });
 
     test('versioning', function() {
-      var callback = sinon.spy();
+      var callback = sandbox.spy();
       Gerrit.install(callback, '0.0pre-alpha');
       assert(callback.notCalled);
     });
@@ -222,6 +223,7 @@ limitations under the License.
     test('_pluginInstalled', function(done) {
       stub('gr-reporting', {
         pluginsLoaded: function() {
+          assert.equal(Gerrit._pluginsPending, 0);
           done();
         }
       });
@@ -232,18 +234,33 @@ limitations under the License.
     });
 
     test('install calls _pluginInstalled', function() {
-      var stub = sinon.stub(Gerrit, '_pluginInstalled');
+      sandbox.stub(Gerrit, '_pluginInstalled');
       Gerrit.install(function(p) { plugin = p; }, '0.1',
           'http://test.com/plugins/testplugin/static/test.js');
-      assert.isTrue(stub.calledOnce);
-      stub.restore();
+      assert.isTrue(Gerrit._pluginInstalled.calledOnce);
     });
 
     test('install calls _pluginInstalled on error', function() {
-      var stub = sinon.stub(Gerrit, '_pluginInstalled');
+      sandbox.stub(Gerrit, '_pluginInstalled');
       Gerrit.install(function() {}, '0.0pre-alpha');
-      assert.isTrue(stub.calledOnce);
-      stub.restore();
+      assert.isTrue(Gerrit._pluginInstalled.calledOnce);
+    });
+
+    test('installGwt calls _pluginInstalled', function() {
+      sandbox.stub(Gerrit, '_pluginInstalled');
+      Gerrit.installGwt();
+      assert.isTrue(Gerrit._pluginInstalled.calledOnce);
+    });
+
+    test('installGwt returns a stub object', function() {
+      var plugin = Gerrit.installGwt();
+      sandbox.stub(console, 'warn');
+      assert.isAbove(Object.keys(plugin).length, 0);
+      Object.keys(plugin).forEach(function(name) {
+        console.warn.reset();
+        plugin[name]();
+        assert.isTrue(console.warn.calledOnce);
+      });
     });
   });
 </script>

polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js

@@ -14,6 +14,16 @@
 (function(window) {
   'use strict';
 
+  var warnNotSupported = function(opt_name) {
+    console.warn('Plugin API method ' + (opt_name || '') + ' is not supported');
+  };
+
+  var stubbedMethods = ['_loadedGwt', 'screen', 'settingsScreen', 'panel'];
+  var GWT_PLUGIN_STUB = {};
+  stubbedMethods.forEach(function(name) {
+    GWT_PLUGIN_STUB[name] = warnNotSupported.bind(null, name);
+  });
+
   var API_VERSION = '0.1';
 
   // GWT JSNI uses $wnd to refer to window.
@@ -98,7 +108,13 @@
 
     // TODO(andybons): Polyfill currentScript for IE10/11 (edge supports it).
     var src = opt_src || (document.currentScript && document.currentScript.src);
-    callback(new Plugin(src));
+    var plugin = new Plugin(src);
+    try {
+      callback(plugin);
+    } catch (e) {
+      console.warn(plugin.getPluginName() + ' install failed: ' +
+          e.name + ': ' + e.message);
+    }
     Gerrit._pluginInstalled();
   };
 
@@ -106,9 +122,14 @@
     return document.createElement('gr-rest-api-interface').getLoggedIn();
   };
 
+  /**
+   * Polyfill GWT API dependencies to avoid runtime exceptions when loading
+   * GWT-compiled plugins.
+   * @deprecated Not supported in PolyGerrit.
+   */
   Gerrit.installGwt = function() {
-    // NOOP since PolyGerrit doesn’t support GWT plugins.
     Gerrit._pluginInstalled();
+    return GWT_PLUGIN_STUB;
   };
 
   Gerrit._allPluginsPromise = null;