Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

[Joost Kremers]

Hi all,

I'm running into a strange problem that I cannot explain. I'm trying to
add some font-lock keywords through a minor mode.[1] I activate the
minor mode by putting it in the hook of a particular major mode, and the
minor mode activation function calls font-lock-add-keywords with the
proper arguments.

Everything works fine if I call the major mode function interactively
(`M-x markdown-mode', to be precise). The minor mode is activated and
the font-lock keywords are added correctly.

However, if `markdown-mode' is activated through `auto-font-alist', the
additional font-lock keywords are not added.

More precisely, they seem to be added and immediately removed again.
This at least is suggested by my debug efforts: I've added some code to
the function that activates the additional font-lock keywords that saves
the buffer-local value of font-lock-keywords to another variable. When I
check this variable's value after loading a markdown file, the
additional keywords are there. Checking the value of
`font-lock-keywords' at this point shows that the additional keywords
are not there (anymore).

I tried to see if there's anything in my init file that interferes, but
that doesn't seem to be the case. The problem still occurs, even if I
reduce my init file to the following:

,----
| (load-library "/path/to/markdown-mode")
| (load-library "/path/to/pandoc-mode")
| (add-to-list 'auto-mode-alist '("\\.text\\'" . markdown-mode))
| (add-hook 'markdown-mode-hook 'pandoc-mode)
`----

Does anyone have an idea where I should look further to debug this
issue? I looked at the code for `set-auto-mode', but couldn't find
anything suspicious...

TIA

Joost




[1] In particular, pandoc-mode:

    https://github.com/joostkremers/pandoc-mode

    The code adding the font-lock keywords is here:

    https://github.com/gbgar/pandoc-mode/commit/a66726170e8db5928e6778f671b4ccfe663a5379

-- 
Joost Kremers                                   joostkremers@fastmail.fm
Selbst in die Unterwelt dringt durch Spalten Licht
EN:SiS(9)

Re: Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

[Dmitry Gutov]

On 01/26/2015 01:28 PM, Joost Kremers wrote:

> Everything works fine if I call the major mode function interactively
> (`M-x markdown-mode', to be precise). The minor mode is activated and
> the font-lock keywords are added correctly.
>
> However, if `markdown-mode' is activated through `auto-font-alist', the
> additional font-lock keywords are not added.

I can reproduce this, looks like a bug.

Re: Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

[Michael Heerdegen]

Dmitry Gutov <dgutov@yandex.ru> writes:

> I can reproduce this, looks like a bug.

Could that be another occurrence of the "changing major mode kills all
local variables" thing?

Re: Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

[Dmitry Gutov]

On 01/26/2015 05:13 PM, Michael Heerdegen wrote:
> Dmitry Gutov <dgutov@yandex.ru> writes:
>
>> I can reproduce this, looks like a bug.
>
> Could that be another occurrence of the "changing major mode kills all
> local variables" thing?

Now sure what previous occurrence you're referring to, but killing 
happens before the major mode function runs, not after. Right?

Re: Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

[Stefan Monnier]

>> I can reproduce this, looks like a bug.
> Could that be another occurrence of the "changing major mode kills all
> local variables" thing?

No, it looks more like when global-font-lock-mode's hook runs, it
gets fooled into thinking that the font-lock-keywords was setup for
a parent mode and needs to be re-set.


        Stefan

Re: Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

[Joost Kremers]

Michael Heerdegen wrote:
> Dmitry Gutov <dgutov@yandex.ru> writes:
>
>> I can reproduce this, looks like a bug.
>
> Could that be another occurrence of the "changing major mode kills all
> local variables" thing?

Well, if it works when `markdown-mode' is called manually (`M-x
markdown-mode'), what is different about activating `markdown-mode'
through `auto-mode-alist'?



-- 
Joost Kremers                                   joostkremers@fastmail.fm
Selbst in die Unterwelt dringt durch Spalten Licht
EN:SiS(9)

Re: Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

[Michael Heerdegen]

Dmitry Gutov <dgutov@yandex.ru> writes:

> Now sure what previous occurrence you're referring to, but killing
> happens before the major mode function runs, not after. Right?

You're probably right, I was just guessing.

Re: Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

[Joost Kremers]

Stefan Monnier wrote:
>>> I can reproduce this, looks like a bug.
>> Could that be another occurrence of the "changing major mode kills all
>> local variables" thing?
>
> No, it looks more like when global-font-lock-mode's hook runs, it
> gets fooled into thinking that the font-lock-keywords was setup for
> a parent mode and needs to be re-set.

So should I file a bug report?


-- 
Joost Kremers                                   joostkremers@fastmail.fm
Selbst in die Unterwelt dringt durch Spalten Licht
EN:SiS(9)

Re: Possible bug? font-lock-add-keywords in minor mode and auto-mode-alist

[Dmitry Gutov]

On 01/27/2015 10:36 PM, Joost Kremers wrote:

>> No, it looks more like when global-font-lock-mode's hook runs, it
>> gets fooled into thinking that the font-lock-keywords was setup for
>> a parent mode and needs to be re-set.
>
> So should I file a bug report?

That's usually a good idea.