Issue 5660 - Check for runtime.getBrowserInfo API support

templates/geckoInfo.js.tmpl

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 exports.addonName = {{ basename|json }};
 exports.addonVersion = {{ version|json }};
 
 exports.application = "unknown";
 exports.applicationVersion = "0";
 
 exports.platform = "gecko";
 exports.platformVersion = "0";
 
 let match = /\brv:(\d+(?:\.\d+)?)\b/.exec(navigator.userAgent);
 if (match)
   exports.platformVersion = match[1];
 
-browser.runtime.getBrowserInfo().then(browserInfo =>
+let exportApplicationInfo = info =>
 {
-  exports.application = browserInfo.name.toLowerCase();
-  exports.applicationVersion = browserInfo.version;
-});
+  exports.application = info.name.toLowerCase();
+  exports.applicationVersion = info.version;
+};
+
+// Firefox 50 does not support runtime.getBrowserInfo
+if ("getBrowserInfo" in browser.runtime)
+{
+  browser.runtime.getBrowserInfo().then(exportApplicationInfo);
+}
+else
+{
+  // Based on the Firefox UA string reference:
+  // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/User-Agent/Firefox
+  // The regular expression here will capture the "appname/appversion" part of
+  // "Mozilla/5.0 (platform; rv:geckoversion) Gecko/geckotrail
+  // Firefox/firefoxversion appname/appversion" if present, otherwise it'll
+  // capture "Firefox/firefoxversion"
+  let browserInfo =
+    /\brv:(?:\d+(?:\.\d+)?)\) [^\/]+\/[^ ]+(?: ([^\/]+)\/([^ ]+))+\b/
+    .exec(navigator.userAgent);
+  if (browserInfo)
+    exportApplicationInfo({name: browserInfo[1], version: browserInfo[2]});

[Sebastian Noack, 2017/09/13 17:38:01]

There is only one application this code is possibly running on, i.e. Firefox on
desktop. Firefox Mobile didn't support WebExtensions before version 54 (which
already has runtime.getBrowserInfo), and Adblock Plus won't load before version
55, anyway. Other Gecko applications don't have WebExtension support to date.

Even if this code could run on Firefox Mobile, your logic wouldn't detect it, as
the user agent string looks like "Mozilla/5.0 (Android 4.4; Mobile; rv:41.0)
Gecko/41.0 Firefox/41.0".

So it is safe (if not even more reliable) to hard-code Firefox as the
application here, which will also simplify the detection of the version:

  if ("getBrowserInfo" in browser.runtime)
  {
    browser.runtime.getBrowserInfo().then(browserInfo =>
    {
      exports.application = browserInfo.name.toLowerCase();
      exports.applicationVersion = browserInfo.version;
    });
  }
  else
  {
    exports.application = "firefox";
    let match = /\bFirefox\/(\S+)/.exec(avigator.userAgent);
    if (match)
      exports.applicationVersion = match[1];
  }

[Manish Jethani, 2017/09/14 04:27:11]

Hypothetically, suppose other Gecko-based browsers start supporting
WebExtensions at some point, then for the UA string "Mozilla/5.0 (Macintosh;
Intel Mac OS X 10.5; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 Camino/2.2.1", we
want the application/version to be Firefox 4.0.1 or Camino 2.2.1?

Anyway, if it's only going to run on Firefox for now then I guess it's OK to
just query the Firefox version number. I'll make the change.

[Sebastian Noack, 2017/09/14 04:33:41]

This would only be relevant in the unlikely case that browser is using Gecko 50.
Older versions are not supported by anyway. On newer versions we'd use
runtime.getBrowserInfo().

[Manish Jethani, 2017/09/14 06:06:50]

Done.

+}