On 14-Apr-2018 20:39 +0200, Christian Brabandt wrote:
>
> On Sa, 14 Apr 2018, Ivan Brennan wrote:
>
>> When your plugin wants to provide an event the user can hook into, it could
>> broadcast a User autocommand:
>>
>> function! foo#do_it()
>> call s:do_thing()
>> doautocmd User FooDidIt
>> endfunction
>>
>> If the user's vimrc contains,
>>
>> augroup MyGroup
>> autocmd!
>> autocmd User FooDidIt call MyHandler()
>> augroup END
>>
>> then MyHandler() will be called any time foo#do_it() runs.
>>
>> If the user *does not* set up any such autocommand, however, any time
>> foo#do_it() runs, Vim displays "No matching autocommands".
>>
>> You could suppress these messages by prefixing doautocmd with "silent", but
>> that would also suppress any messages a handler tries to display. So most
>> plugins wrap doautocmd in a conditional:
>>
>> function! foo#do_it()
>> call s:do_thing()
>> if exists('#User#FooThing')
>> doautocmd User FooThing
>> endif
>> endfunction
>>
>> When providing an event the user can hook into, I'd think it's better to
>> decouple the plugin from any knowledge/concern about what, if anything, has
>> been set up to listen for the event. But we're forced to run this check,
>> given how doautocmd works.
>>
>> More importantly, the exists() check is inaccurate in some cases. For
>> example, the following are two autocommand definitions are equivalent,
>>
>> autocmd User FooBar,FooBaz call MyHandler()
>> autocmd User Foo{Bar,Baz} call MyHandler()
>>
>> but exists('#User#FooBar') will return true for the first and false for the
>> second.
>>
>> I can see the usefulness of displaying No matching autocommands for
>> debugging purposes, but beyond that it seems like bad behavior.
>>
>> Am I thinking about this the wrong way?
>
> You are probably right. However most plugins I have seen usually do not
> bother and use `:sil doautocmd User ...` So perhaps nothing to worry
> about?
I agree to both of you. The behavior is unfortunate, and most plugins
(including my own) seem to use :silent doautocmd User. Usually, hooks do
not need to print any messages to users, and if they really need to,
they could use :unsilent, right? Too bad this wasn't better thought
through from the beginning, but I also wonder whether changing this now
would make a difference.
-- regards, ingo
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