Fix company backends setting

[gilbertw1]

After doing a bit of debugging I noticed the the :company-backend setting is not correctly adding individual backends, but is instead always appending the entire list of backends.

For example, after executing the following line:

 (set! :company-backend 'scala-mode '(ensime-company company-yasnippet)))

The company-backends var for scala mode will look like:

'((ensime-company company-yasnippet)
   backend1 backend2 backend...)

What I would expect to happen would be that the value would look like:

'(ensime-company company-yasnippet backend1 backend2 backend...)

I've updated the def-setting! so that it will add these values into the existing flat structure, and now has the additional benefit preventing duplicate backends from being added to the list. Additionally, I've included in this pull request the removal of the explicit add of the ensime-company backend, since it's already added when ensime-mode is enabled.

[hlissner]

This was intentional. Company backends are OR'ed, i.e. backend1 OR backend2 OR backend3. So later backends won't run unless earlier ones fail.

Backends in sublists are merged together. i.e. (backend1 UNION backend2) OR backend3, which I think is desirable.

However, I do see a possible improvement to :company-backend to allow:

;; prepends multiple symbols
(set! :company-backend 'scala-mode 'ensime-company 'company-yasnippet)
;; company-backends: (ensime-company company-yasnippet ...)

;; pushes a sublist
(set! :company-backend 'scala-mode '(ensime-company company-yasnippet))
;; company-backends: ((ensime-company company-yasnippet) ...)

Additionally, I've included in this pull request the removal of the explicit add of the ensime-company backend, since it's already added when ensime-mode is enabled.

I can't say I'm a fan of (ensime-company-enable) (which ensime-mode uses to set up company):

1. It only adds company-ensime. My setting adds (company-ensime company-yasnippet).
2. it rebinds TAB to ensime-company-complete-or-indent (i.e. whether the user likes it or not).

I think it's better to leave it to :company-backend. Ensime can be told not to interfere with (setq ensime-completion-style nil) with no ill effects to completion in general.

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Thanks for pointing this out, but I can't accept the PR.

[gilbertw1]

Ah my bad, thanks for the response!

This totally explains the behavior I was seeing. RTFM :)