[PATCH] ui: don't read the same config file twice

[Ryan McElroy]

On 3/13/17 7:56 PM, Jun Wu wrote:
> This is a BC because loading order matters:
>
>    # a.rc
>    %include b.rc
>    [ui]
>    editor = foo
>    %include b.rc
>
>    # b.rc
>    [ui]
>    editor = bar
>
> Since people should be able to arrange config files in a way that no files
> are included twice. I prefer not being too smart in hg.

I agree with Jun that we need preserve last-loaded-wins semantics. We 
could still build single-loading if we read config files once, kept them 
in separate dicts in an ordered set, and just reordered to the end of a 
list when re-read, and once all configs are read, then combine the dicts 
in list order, but that sounds a bit complex.

I'd still be supportive of that direction if there's a perf win though.

>
> Excerpts from David Soria Parra's message of 2017-03-13 19:47:47 -0700:
>> # HG changeset patch
>> # User David Soria Parra <davidsp at fb.com>
>> # Date 1489459557 25200
>> #      Mon Mar 13 19:45:57 2017 -0700
>> # Node ID 7e2222599b4f534e27a0462bb1263208cc1c8d71
>> # Parent  3d3109339b57341b333c1112beb41dd281fa944a
>> ui: don't read the same config file twice
>>
>> During dispatch and localrepo setup we might read the same file twice if
>> the repository we are loading is the currnet working directory/.hg which is the

Typo: current is misspelled

>> default case. We now keep a set of filenames we read around and abort

We don't abort, we return early. Abort would imply raising an 
error.Abort (the way I inrepretted it anyway).

>> if we read the config already. It would be nice to do this in a decorator,
>> but I have not found a reliable, simple way to hash arguments.
>>
>> diff --git a/mercurial/ui.py b/mercurial/ui.py
>> --- a/mercurial/ui.py
>> +++ b/mercurial/ui.py
>> @@ -160,6 +160,7 @@
>>           self._colormode = None
>>           self._terminfoparams = {}
>>           self._styles = {}
>> +        self._readfilenames = set()
>>   
>>           if src:
>>               self.fout = src.fout
>> @@ -258,6 +259,9 @@
>>   
>>       def readconfig(self, filename, root=None, trust=False,
>>                      sections=None, remap=None):
>> +        if filename in self._readfilenames:
>> +            return
>> +
>>           try:
>>               fp = open(filename, u'rb')
>>           except IOError:
>> @@ -304,6 +308,7 @@
>>           if root is None:
>>               root = os.path.expanduser('~')
>>           self.fixconfig(root=root)
>> +        self._readfilenames.add(filename)
>>   
>>       def fixconfig(self, root=None, section=None):
>>           if section in (None, 'paths'):