On https://wiki.mozilla.org/WebExtensions, we claim to support chrome.i18n.getMessage() with "@@extension_id" and "@@ui_locale" predefined messages. These appear to work in background scripts. The Chrome docs at https://developer.chrome.com/extensions/content_scripts state that the i18n API should be available to content_scripts. In Firefox, it is not. Steps to Reproduce: 1. In a content script, call console.log("@@extension_id is", chrome.i18n.getMessage("@@extension_id")); What should happen: - A uuid should get logged to the console What actually happens: - "chrome.i18n is undefined" shows up in the Browser Console This causes the Reddit Enhancement Suite to throw: https://github.com/honestbleeps/Reddit-Enhancement-Suite/blob/v4.5.4/Chrome/browsersupport-chrome.js#L116 Test case in the "i18n_content_script" folder of https://github.com/callahad/webextension-tests

This no longer blocks 1208765, as RES has moved away from this API.

Bug 1208761: [webext] Support l10n.getMessage in content scripts. r?billm

Comment on attachment 8691163 [details] MozReview Request: Bug 1208761: [webext] Support l10n.getMessage in content scripts. r?billm https://reviewboard.mozilla.org/r/26081/#review23459 ::: toolkit/components/extensions/test/mochitest/test_ext_i18n.html:83 (Diff revision 1) > + if (actual !== expected) { Can you just send a message to the extension that includes actual and expected? Then the extension could do assertEq. That way we get a message printed when the test succeeds. The downside is that actual and expected must support structured clone. But in this case I can't see how they wouldn't.

https://hg.mozilla.org/integration/fx-team/rev/4dca10306d58d2e87cbed46a72472b62c17b0ec9 Bug 1208761: [webext] Support l10n.getMessage in content scripts. r=billm

Updated https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Chrome_incompatibilities