Autocomplete Mode is an Emacs mode that tries to guess what word you’re typing and provide auto-completion. Recently, it started failing in simple scenarios.

It can use various ‘sources’ to try to figure out what you’re about to type. The simplest source is ac-source-dictionary which is a simple list of words. If you start typing any of those words, it will try to autocomplete them for you. Normally, you’d put those words in a file, with each word on a separate line, but for testing purposes, you can also add them manually using an elisp function. Here’s the test that failed for me:

(add-to-list 'ac-user-dictionary "foobar@example.com")

That adds the email address to the dictionary. Then, typing ‘foo’ in any buffer, should offer to autocomplete the entire email address. Unfortunately, it wasn’t working.

To debug, I typed ‘foo’ and then did M-x auto-complete, which forces auto-complete to look for a completion. This resulted in an error in the Minibuffer:

ac-yasnippet-candidates: Symbol's function definition is void: yas/current-snippet-table

This led me to check which ‘sources’ autocomplete was trying to use: C-h v ac-sources

(ac-source-features ac-source-functions ac-source-yasnippet
 ac-source-variables ac-source-symbols ac-source-abbrev
 ac-source-dictionary ac-source-words-in-same-mode-buffers)

So, autocomplete is looking through each one of those sources, trying to find possible words I might be typing. The third one is called ac-source-yasnippet, which seems to be where my error is coming from.

So, I looked into the yasnippet source code and found that, indeed, there was no function named yas/current-snippet-table. That function has been renamed to yas--get-snippets-table in version 0.8.0, but autocomplete is still relying on the old function name. (RANT: Don’t rename functions that others might be using without providing some kind of alias, at least temporarily) I looked at the code for autosnippet on github and noted that the latest version has been fixed to use the new code, but it hasn’t yet been released on MELPA. Until it is, the quick solution is to remove ac-source-yasnippet from ac-sources.

(delq 'ac-source-yasnippet ac-sources)

Then typing ‘foo’ autocompletes to ‘foobar@example.com’.

It seems that autocomplete should be more forgiving of errors in any specific ‘source’, passing it up to use other sources. Alternatively, it should fail loudly when there’s an error, so that I can know to fix or remove the offending ‘source’.