Thunderbird/Add-ons Guide 57

Add-ons Guide for Thunderbird 57 and beyond

Mozilla core have disabled "legacy" add-ons (not based purely on WebExtensions) in Firefox 57. Because this type of add-on is not supported from mozilla57 any more, many interfaces have been removed from Mozilla core.

However, Thunderbird 57-59 and Seamonkey still support these add-ons if the appropriate modifications are done to adapt to the changed interfaces. In general, Thunderbird is adding WebExtension support (bug 1396172) while maintaining "legacy" add-ons and hybrid add-ons.

Removed interfaces in mozilla57

• nsILocalFile -- replacement: nsIFile
• extIApplication, nsIEntityConverter
• nsIProgrammingLanguage
• nsILocaleService and friends
• nsIScriptableDateFormat -- replacement: Intl.DateTimeFormat and mozIntl.DateTimeFormat
• nsIFilePicker.show() -- replacement: nsIFilePicker.open() (async), example: Changeset where Thunderbird implemented that change. There's also a "lazy" replacement:

function PickerShow(fp) {
  let done = false;
  let rv, result;
  fp.open(result => {
    rv = result;
    done = true;
  });
  let thread = Components.classes["@mozilla.org/thread-manager;1"]
                         .getService().currentThread;
  while (!done) {
    thread.processNextEvent(true);
  }
  return rv;
}

• nsIDownloadManager
• Promise.jsm -- replacement: PromiseUtils.jsm
• nsIPrefBranch2 and nsIPrefBranchInternal -- replacement: nsIPrefBranch
• nsIExternalProtocolService.loadUrl -- replacement: nsIExternalProtocolService.loadURI
• nsIInputStreamPump.init: Change of arguments
• nsIAtomService - see bug 1393692 for removal from Thunderbird

Changes to JS and XUL in mozilla57

[1]

• `for each ()` construct [2] -- replacement: 'for (x of object)' or 'for (x of Object.values())'
• `with` construct [3]
• catch (ex if ex instanceof ExceptionType) (removed in mozilla47 already)
• versioned Javascript support -- replacement: In XUL files, links to JS files using <script type="application/x-javascript" ... > or <script type="application/x-javascript;version=1.7" ... >, change to <script type="application/javascript" ... >
• __iterator__ and Iterator()
• "legacy" generators, now need to use `function*` syntax (removed in mozilla? already)
• imports must be 100% correct now: Components.utils.import("resource://gre/modules/...") for Mozilla central imports, Components.utils.import("resource:///modules/...") for Thunderbird imports.

Changes in thunderbird57

• steelIApplication (removed due to removal of extIApplication) -- replacement: Services, AppConstants
• for (x in fixIterator(obj)) (removed due to removal of __iterator__) -- replacement: for (x of fixIterator(obj))

Removed in mozilla58

• Date.prototype.toLocaleFormat
• {get,set}ComplexValue use of nsISupportsString -- replacement: {get,set}StringPref(), example: Changeset where Thunderbird implemented that change
• Mechanism to store add-on preferences in defaults/preferences/xx.js. Thunderbird 58 Beta not affected (beta 1+2: backout of this core change, beta 3 has fix from TB 59). A fix has landed on Daily 59 as of 2017-12-12, see bug 1414398.

Changes to JS in mozilla58

[4]

• StopIteration [5]

Removed in mozilla59

• Dialog (optionsType=1) and Inline (2) options were removed in bug 1414406. Thunderbird will not support that feature any more, only options in tabs (3) work now. Replacements:

1. If addon's install.rdf contains no <em:optionsType> declaration, the addon's preferences page (<em:optionsURL>) will only be accessible via a new submenu in Tools menu (implemented in bug 1419145, landed on Daily 59 as of 2017-12-22). The preferences will open in a dialog, as was the case in older versions.
   
2. If addon's install.rdf contains <em:optionsType>3</em:optionsType>, the Preferences button will appear in the Add-on Manager tab besides the addon, as was the case in older versions. Clicking the button will open the preferences page in a new tab. The preferences page (optionsURL) is also accessible via the new submenu in Tools menu and will open in a tab. No other value of <em:optionsType> is supported and TB will even refuse to install such addons (decision from bug 1414406).
3. Alternatively, add-ons may embed a WebExtension to display inline options [6][7]. This should be working now that bug 1418914 has been fixed.

Changes to JS changes in mozilla59

[8]

• catch (ex if ...)

Outlook and Suggestion

Suggestion for add-on authors wishing to be compatible with Thunderbird 59: Go, go, go! The fix for bug 1414398 (default preferences) and bug 1419145 (menu to access add-on options, tab options (3) work) has arrived (2017-12-12 and 2017-12-22). bug 1418914 has been fixed and then inline options can be achieved via an embedded WebExtension. We will prepare a sample of how this is done in early 2018. All add-ons compatible with TB 58 beta should also be compatible with TB 59 Daily.

Also Note

The list above only contains selected changes relevant to add-ons. The full list of changes can be seen at Firefox developer release notes where all the details, bugzilla bug reports and patches implementing those changes can be found.