[PATCH] match: introduce nevermatcher for when no ignore files are present

[Martin von Zweigbergk]

On Thu, Jun 1, 2017 at 7:19 AM, Augie Fackler <raf at durin42.com> wrote:
> On Thu, Jun 01, 2017 at 12:41:16AM -0700, Siddharth Agarwal wrote:
>> # HG changeset patch
>> # User Siddharth Agarwal <sid0 at fb.com>
>> # Date 1496302852 25200
>> #      Thu Jun 01 00:40:52 2017 -0700
>> # Node ID 14f332c8fe10c498e7c35bef09e53b8b6c7e5f43
>> # Parent  dbf330cadc5a3c0707c4611f2f4150be13cac02a
>> match: introduce nevermatcher for when no ignore files are present

Great, I had meant to add this anyway, but I didn't know I had a reason to :-)

>
> Queued, thanks.
>
>> 952017471f93 introduced a deterministic `__repr__` for ignores. However, it
>> didn't account for when ignore was `util.never`.

Oh, sorry about that, I had no idea it could be anything other than a matcher.

>> This broke fsmonitor's ignore
>> change detection -- with an empty hgignore, it would kick in all the time.
>>
>> Introduce `nevermatcher` and switch to it. This neatly parallels
>> `alwaysmatcher`.
>>
>> diff --git a/mercurial/dirstate.py b/mercurial/dirstate.py
>> --- a/mercurial/dirstate.py
>> +++ b/mercurial/dirstate.py
>> @@ -232,7 +232,7 @@ class dirstate(object):
>>      def _ignore(self):
>>          files = self._ignorefiles()
>>          if not files:
>> -            return util.never
>> +            return matchmod.never(self._root, '')
>>
>>          pats = ['include:%s' % f for f in files]
>>          return matchmod.match(self._root, '', [], pats, warn=self._ui.warn)
>> diff --git a/mercurial/match.py b/mercurial/match.py
>> --- a/mercurial/match.py
>> +++ b/mercurial/match.py
>> @@ -175,6 +175,9 @@ def exact(root, cwd, files, badfn=None):
>>  def always(root, cwd):
>>      return alwaysmatcher(root, cwd)
>>
>> +def never(root, cwd):
>> +    return nevermatcher(root, cwd)
>> +
>>  def badmatch(match, badfn):
>>      """Make a copy of the given matcher, replacing its bad method with the given
>>      one.
>> @@ -339,6 +342,25 @@ class alwaysmatcher(basematcher):
>>      def __repr__(self):
>>          return '<alwaysmatcher>'
>>
>> +class nevermatcher(basematcher):
>> +    '''Matches nothing.'''
>> +
>> +    def __init__(self, root, cwd, badfn=None, relativeuipath=False):
>> +        super(nevermatcher, self).__init__(root, cwd, badfn,
>> +                                           relativeuipath=relativeuipath)
>> +
>> +    def always(self):
>> +        return False
>> +
>> +    def matchfn(self, f):
>> +        return False
>> +
>> +    def visitdir(self, dir):
>> +        return False

These three are all copying the behavior from basematcher. I'll
rewrite the queued commit. I'll also update the existing comment that
says 'probably adding a "nevermatcher"' to say 'using nevermatcher'
now that it exists :-)

>> +
>> +    def __repr__(self):
>> +        return '<nevermatcher>'
>> +
>>  class patternmatcher(basematcher):
>>
>>      def __init__(self, root, cwd, kindpats, ctx=None, listsubrepos=False,
>> diff --git a/tests/test-hgignore.t b/tests/test-hgignore.t
>> --- a/tests/test-hgignore.t
>> +++ b/tests/test-hgignore.t
>> @@ -1,6 +1,10 @@
>>    $ hg init ignorerepo
>>    $ cd ignorerepo
>>
>> +debugignore with no hgignore should be deterministic:
>> +  $ hg debugignore
>> +  <nevermatcher>
>> +
>>  Issue562: .hgignore requires newline at end:
>>
>>    $ touch foo
>> _______________________________________________
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