ae32f31eb4
http://crbug.com/280464 has been resolved, so we can now use redirectUrl at onHeadersReceived. For backwards-compatibility, the code for the original method has not been removed, and a feature detection script was added that detects whether the desired feature is available.
122 lines
4.0 KiB
JavaScript
122 lines
4.0 KiB
JavaScript
/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
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/*
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Copyright 2014 Mozilla Foundation
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/* globals chrome */
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'use strict';
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var Features = {
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featureDetectLastUA: '',
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// Whether ftp: in XMLHttpRequest is allowed
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extensionSupportsFTP: false,
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// Whether redirectUrl at onHeadersReceived is supported.
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webRequestRedirectUrl: false,
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};
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chrome.storage.local.get(Features, function(features) {
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Features = features;
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if (features.featureDetectLastUA === navigator.userAgent) {
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// Browser not upgraded, so the features did probably not change.
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return;
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}
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var inconclusiveTestCount = 0;
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if (!features.extensionSupportsFTP) {
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features.extensionSupportsFTP = featureTestFTP();
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}
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if (!features.webRequestRedirectUrl) {
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++inconclusiveTestCount;
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// Relatively expensive (and asynchronous) test:
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featureTestRedirectOnHeadersReceived(function(result) {
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// result = 'yes', 'no' or 'maybe'.
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if (result !== 'maybe') {
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--inconclusiveTestCount;
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}
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features.webRequestRedirectUrl = result === 'yes';
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checkTestCompletion();
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});
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}
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checkTestCompletion();
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function checkTestCompletion() {
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// Only stamp the feature detection results when all tests have finished.
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if (inconclusiveTestCount === 0) {
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Features.featureDetectLastUA = navigator.userAgent;
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}
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chrome.storage.local.set(Features);
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}
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});
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// Tests whether the extension can perform a FTP request.
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// Feature is supported since Chromium 35.0.1888.0 (r256810).
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function featureTestFTP() {
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var x = new XMLHttpRequest();
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// The URL does not need to exist, as long as the scheme is ftp:.
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x.open('GET', 'ftp://ftp.mozilla.org/');
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try {
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x.send();
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// Previous call did not throw error, so the feature is supported!
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// Immediately abort the request so that the network is not hit at all.
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x.abort();
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return true;
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} catch (e) {
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return false;
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}
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}
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// Tests whether redirectUrl at the onHeadersReceived stage is functional.
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// Feature is supported since Chromium 35.0.1911.0 (r259546).
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function featureTestRedirectOnHeadersReceived(callback) {
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// The following URL is really going to be accessed via the network.
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// It is the only way to feature-detect this feature, because the
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// onHeadersReceived event is only triggered for http(s) requests.
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var url = 'http://example.com/?feature-detect-' + chrome.runtime.id;
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function onHeadersReceived(details) {
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// If supported, the request is redirected.
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// If not supported, the return value is ignored.
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return {
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redirectUrl: chrome.runtime.getURL('/manifest.json')
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};
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}
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chrome.webRequest.onHeadersReceived.addListener(onHeadersReceived, {
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types: ['xmlhttprequest'],
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urls: [url]
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}, ['blocking']);
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var x = new XMLHttpRequest();
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x.open('get', url);
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x.onloadend = function() {
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chrome.webRequest.onHeadersReceived.removeListener(onHeadersReceived);
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if (!x.responseText) {
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// Network error? Anyway, can't tell with certainty whether the feature
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// is supported.
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callback('maybe');
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} else if (/^\s*\{/.test(x.responseText)) {
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// If the response starts with "{", assume that the redirection to the
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// manifest file succeeded, so the feature is supported.
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callback('yes');
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} else {
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// Did not get the content of manifest.json, so the redirect seems not to
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// be followed. The feature is not supported.
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callback('no');
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}
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};
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x.send();
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}
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