Issue 6539, 6782 - Implement support for snippets

lib/snippets.js

+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-present eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+"use strict";
+
+const {defaultMatcher} = require("matcher");
+const {RegExpFilter, WhitelistFilter} = require("filterClasses");
+const {extractHostFromFrame, getDecodedHostname,
+       isThirdParty, stringifyURL} = require("url");
+const {checkWhitelisted} = require("whitelisting");
+const {FilterNotifier} = require("filterNotifier");
+const devtools = require("devtools");
+
+const {typeMap} = RegExpFilter;
+
+let library = null;
+
+fetch(browser.extension.getURL("/snippets.js"), {cache: "no-cache"})

[Manish Jethani, 2018/03/30 20:33:15]

Using the fetch API to load the snippets library. We could also use
XMLHttpRequest or something similar.

[Manish Jethani, 2018/03/30 20:39:25]

So this is literally just a file that is bundled with the extension. In the
future (version 2) we want to be able to update the snippets library
dynamically.

+.then(response => response.text())
+.then(text =>
+{
+  library = text;

[Manish Jethani, 2018/03/30 20:33:15]

The "library" is the entire text of the file. See ./snippets.js for an example.
It's a file that defines an anonymous object, each of the properties of which is
a function.

e.g.

  {
    hello()
    {
      console.log("Hello, world!");
    }
  }

+});
+
+function injectCode(snippet, tabId, frameId)
+{
+  if (!library)
+    return;
+
+  let name = snippet.replace("\"", "\\\"");

[Manish Jethani, 2018/03/30 20:33:15]

The name could contains quotes so we need to escape those. Actually we should
escape any non-whitespace escapable characters.

[Manish Jethani, 2018/03/31 08:09:40]

It turns out the correct way to quote a string is using JSON.stringify. Done.

+
+  browser.tabs.executeScript(tabId, {
+    code: `((${library})["${name}"] || (() => {}))()`,
+    frameId,
+    matchAboutBlank: true,
+    runAt: "document_start"
+  });
+}
+
+browser.webNavigation.onCommitted.addListener(details =>
+{
+  // There's a bug in Chrome that causes webNavigation.onCommitted to get
+  // dispatched twice if there's a URL filter present, therefore we must listen
+  // for all URLs and do an explicit check here.
+  if (!/^https?:\/\//.test(details.url))

[Manish Jethani, 2018/03/30 20:33:15]

I'll try to make a standalone test case for this and log it in the Chromium
bugbase.

+    return;
+
+  let url = new URL(details.url);
+  let urlString = stringifyURL(url);
+  let parentFrame = ext.getFrame(details.tabId, details.parentFrameId);
+  let hostname = extractHostFromFrame(parentFrame) || getDecodedHostname(url);
+  let thirdParty = isThirdParty(url, hostname);
+
+  let filter = defaultMatcher.matchesAny(urlString, typeMap.SNIPPET, hostname,
+                                         thirdParty, null, true);

[Manish Jethani, 2018/03/30 20:39:25]

Note that here we're explicitly asking for domain-specific filters. I'm not sure
if generic filters make sense here, but we could keep it domain-specific for the
initial implementation anyway.

+  if (!filter)
+    return;
+
+  let page = new ext.Page({id: details.tabId, url: details.url});
+  let frame = ext.getFrame(details.tabId, details.frameId);
+
+  if (checkWhitelisted(page, frame))
+    return;
+
+  devtools.logRequest(page, urlString, "SNIPPET", hostname, thirdParty, null,
+                      true, filter);
+  FilterNotifier.emit("filter.hitCount", filter, 0, 0, page);
+
+  if (filter instanceof WhitelistFilter)
+    return;
+
+  for (let snippet of filter.snippets)
+    injectCode(snippet, details.tabId, details.frameId);
+});