opendev/gerrit
Code Issues Proposed changes

Address race condition in HLJS loader

Browse Source 
Tapping the "Show Diffs" link in the change view to display all of a
change's diffs inline spawns several asynchronous syntax highlighting
processes. Sometimes (especially for long file lists and slower HLJS
download rates) multiple highlight processes would request HLJS before
it had been loaded, resulting in multiple load/definitions of the
library. Occasionally this would result in a JS exception.

With this change, the HLJS loader functionality of GR-SYNTAX-LAYER is
separated into the GR-SYNTAX-LIB-LOADER component. This component
employs a singleton property to track state across multiple lib requests
behind a promise interface.

Tests are updated.

Change-Id: I673998d406a33afa158e04c4dbb91fe31442d527
This commit is contained in:
Wyatt Allen
2016-09-12 14:19:22 -07:00
parent da3a8d32ca
commit e7a51875e6
7 changed files with 223 additions and 44 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.html
View File

@@ -14,7 +14,12 @@ See the License for the specific language governing permissions and
limitations under the License.
-->
<link rel="import" href="../../../bower_components/polymer/polymer.html">
<link rel="import" href="../gr-syntax-lib-loader/gr-syntax-lib-loader.html">
<dom-module id="gr-syntax-layer">
<template>
<gr-syntax-lib-loader id="libLoader"></gr-syntax-lib-loader>
</template>
<script src="../gr-diff/gr-diff-line.js"></script>
<script src="../gr-diff-highlight/gr-annotation.js"></script>
<script src="gr-syntax-layer.js"></script>

49
polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer.js
View File

@@ -106,6 +106,7 @@
value: function() { return []; },
},
_processHandle: Number,
_hljs: Object,
},
addListener: function(fn) {
@@ -278,7 +279,6 @@
_processNextLine: function(state) {
var baseLine = undefined;
var revisionLine = undefined;
var hljs = this._getHighlightLib();
var section = this.diff.content[state.sectionIndex];
if (section.ab) {
@@ -301,15 +301,15 @@
var result;
if (this._baseLanguage && baseLine !== undefined) {
result = hljs.highlight(this._baseLanguage, baseLine, true,
result = this._hljs.highlight(this._baseLanguage, baseLine, true,
state.baseContext);
this.push('_baseRanges', this._rangesFromString(result.value));
state.baseContext = result.top;
}
if (this._revisionLanguage && revisionLine !== undefined) {
result = hljs.highlight(this._revisionLanguage, revisionLine, true,
state.revisionContext);
result = this._hljs.highlight(this._revisionLanguage, revisionLine,
true, state.revisionContext);
this.push('_revisionRanges', this._rangesFromString(result.value));
state.revisionContext = result.top;
}
@@ -358,45 +358,10 @@
});
},
_getHighlightLib: function() {
return window.hljs;
},
_isHighlightLibLoaded: function() {
return !!this._getHighlightLib();
},
_configureHighlightLib: function() {
this._getHighlightLib().configure(
{classPrefix: 'gr-diff gr-syntax gr-syntax-'});
},
_getLibRoot: function() {
if (this._cachedLibRoot) { return this._cachedLibRoot; }
return this._cachedLibRoot = document.head
.querySelector('link[rel=import][href$="gr-app.html"]')
.href
.match(/(.+\/)elements\/gr-app\.html/)[1];
},
_cachedLibRoot: null,
/**
* Load and configure the HighlightJS library. If the library is already
* loaded, then do nothing and resolve.
* @return {Promise}
*/
_loadHLJS: function() {
if (this._isHighlightLibLoaded()) { return Promise.resolve(); }
return new Promise(function(resolve) {
var script = document.createElement('script');
script.src = this._getLibRoot() + HLJS_PATH;
script.onload = function() {
this._configureHighlightLib();
resolve();
}.bind(this);
Polymer.dom(this.root).appendChild(script);
return this.$.libLoader.get().then(function(hljs) {
this._hljs = hljs;
}.bind(this));
}
},
});
})();

4
polygerrit-ui/app/elements/diff/gr-syntax-layer/gr-syntax-layer_test.html
View File

@@ -182,8 +182,8 @@ limitations under the License.
var mockHLJS = getMockHLJS();
var highlightSpy = sinon.spy(mockHLJS, 'highlight');
sandbox.stub(element, '_getHighlightLib',
function() { return mockHLJS; });
sandbox.stub(element.$.libLoader, 'get',
function() { return Promise.resolve(mockHLJS); });
var processNextSpy = sandbox.spy(element, '_processNextLine');
var processPromise = element.process();

20
polygerrit-ui/app/elements/diff/gr-syntax-lib-loader/gr-syntax-lib-loader.html Normal file
View File

@@ -0,0 +1,20 @@
<!--
Copyright (C) 2016 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<link rel="import" href="../../../bower_components/polymer/polymer.html">
<dom-module id="gr-syntax-lib-loader">
<script src="gr-syntax-lib-loader.js"></script>
</dom-module>

93
polygerrit-ui/app/elements/diff/gr-syntax-lib-loader/gr-syntax-lib-loader.js Normal file
View File

@@ -0,0 +1,93 @@
// Copyright (C) 2016 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
(function() {
'use strict';
var HLJS_PATH = 'bower_components/highlightjs/highlight.min.js';
var LIB_ROOT_PATTERN = /(.+\/)elements\/gr-app\.html/;
Polymer({
is: 'gr-syntax-lib-loader',
properties: {
_state: {
type: Object,
// NOTE: intended singleton.
value: {
loaded: false,
loading: false,
callbacks: [],
},
}
},
get: function() {
return new Promise(function(resolve) {
// If the lib is totally loaded, resolve immediately.
if (this._state.loaded) {
resolve(this._getHighlightLib());
return;
}
// If the library is not currently being loaded, then start loading it.
if (!this._state.loading) {
this._state.loading = true;
this._loadHLJS().then(this._onLibLoaded.bind(this));
}
this._state.callbacks.push(resolve);
}.bind(this));
},
_onLibLoaded: function() {
var lib = this._getHighlightLib();
this._state.loaded = true;
this._state.loading = false;
this._state.callbacks.forEach(function(cb) { cb(lib); });
this._state.callbacks = [];
},
_getHighlightLib: function() {
return window.hljs;
},
_configureHighlightLib: function() {
this._getHighlightLib().configure(
{classPrefix: 'gr-diff gr-syntax gr-syntax-'});
},
_getLibRoot: function() {
if (this._cachedLibRoot) { return this._cachedLibRoot; }
return this._cachedLibRoot = document.head
.querySelector('link[rel=import][href$="gr-app.html"]')
.href
.match(LIB_ROOT_PATTERN)[1];
},
_cachedLibRoot: null,
_loadHLJS: function() {
return new Promise(function(resolve) {
var script = document.createElement('script');
script.src = this._getLibRoot() + HLJS_PATH;
script.onload = function() {
this._configureHighlightLib();
resolve();
}.bind(this);
Polymer.dom(document.head).appendChild(script);
}.bind(this));
},
});
})();

95
polygerrit-ui/app/elements/diff/gr-syntax-lib-loader/gr-syntax-lib-loader_test.html Normal file
View File

@@ -0,0 +1,95 @@
<!DOCTYPE html>
<!--
Copyright (C) 2016 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
<title>gr-syntax-lib-loader</title>
<script src="../../../bower_components/webcomponentsjs/webcomponents.min.js"></script>
<script src="../../../bower_components/web-component-tester/browser.js"></script>
<link rel="import" href="gr-syntax-lib-loader.html">
<test-fixture id="basic">
<template>
<gr-syntax-lib-loader></gr-syntax-lib-loader>
</template>
</test-fixture>
<script>
suite('gr-syntax-lib-loader tests', function() {
var element;
var resolveLoad;
var loadStub;
setup(function() {
element = fixture('basic');
loadStub = sinon.stub(element, '_loadHLJS', function() {
return new Promise(function(resolve) {
resolveLoad = resolve;
});
});
// Assert preconditions:
assert.isFalse(element._state.loaded);
assert.isFalse(element._state.loading);
});
teardown(function() {
if (window.hljs) {
delete window.hljs;
}
loadStub.restore();
// Because the element state is a singleton, clean it up.
element._state.loading = false;
element._state.loaded = false;
element._state.callbacks = [];
});
test('only load once', function(done) {
var firstCallHandler = sinon.stub();
element.get().then(firstCallHandler);
// It should now be in the loading state.
assert.isTrue(loadStub.called);
assert.isTrue(element._state.loading);
assert.isFalse(element._state.loaded);
assert.isFalse(firstCallHandler.called);
var secondCallHandler = sinon.stub();
element.get().then(secondCallHandler);
// No change in state.
assert.isTrue(element._state.loading);
assert.isFalse(element._state.loaded);
assert.isFalse(firstCallHandler.called);
assert.isFalse(secondCallHandler.called);
// Now load the library.
resolveLoad();
flush(function() {
// The state should be loaded and both handlers called.
assert.isFalse(element._state.loading);
assert.isTrue(element._state.loaded);
assert.isTrue(firstCallHandler.called);
assert.isTrue(secondCallHandler.called);
done();
});
});
});
</script>

1
polygerrit-ui/app/test/index.html
View File

@@ -64,6 +64,7 @@ limitations under the License.
'diff/gr-ranged-comment-layer/gr-ranged-comment-layer_test.html',
'diff/gr-selection-action-box/gr-selection-action-box_test.html',
'diff/gr-syntax-layer/gr-syntax-layer_test.html',
'diff/gr-syntax-lib-loader/gr-syntax-lib-loader_test.html',
'gr-app_test.html',
'settings/gr-account-info/gr-account-info_test.html',
'settings/gr-email-editor/gr-email-editor_test.html',