Thunderbird/Add-ons Guide 57

Add-ons Guide for Thunderbird 57 and beyond

FIRST DRAFT

Mozilla core have disabled "legacy" add-ons (not based purely on WebExtensions) in Firefox 57. Since this type of add-on is not supported from mozilla57 any more, a lot of 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.

The removed interfaces are:

• Removed in mozilla57:
  • nsILocalFile -- replacement: nsIFile
  • extIApplication, nsIEntityConverter
  • nsIProgrammingLanguage
  • nsILocaleService and friends
  • nsIScriptableDateFormat -- replacement: Intl.DateTimeFormat
  • nsIFilePicker.show() -- replacement: nsIFilePicker.open() (async)
  • nsIDownloadManager
  • Promise.jsm -- replacement: PromiseUtils.jsm
  • nsIPrefBranch2 and nsIPrefBranchInternal -- replacement: nsIPrefBranch
  • nsIExternalProtocolService::LoadUrl -- replacement: nsIExternalProtocolService::LoadURI

• JS and XUL changes 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) (actually 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()

• 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()
  • Mechanism to store add-on preferences in defaults/preferences/xx.js. Thunderbird 58 Beta not affected due to backout of this core change. Work on the way to re-establish this feature, see bug 1414398.

• JS changes in mozilla58 [4]
  • StopIteration [5]

• Removed in mozilla59
  • Inline options. Analysis on the way of how this feature can be restored, see bug 1419145. Current solution: Add-ons need to embed a WebExtension to display an options dialog[6][7], not working due to bug 1418914.

• JS changes in mozilla59 [8]
  • catch (ex if ...)