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

[Martin von Zweigbergk]

On Thu, Jun 1, 2017 at 8:25 AM, Martin von Zweigbergk
<martinvonz at google.com> wrote:
> On Thu, Jun 1, 2017 at 8:24 AM, Martin von Zweigbergk
> <martinvonz at google.com> wrote:
>> 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)
>
> Oh, and do we really need the relativeuipath argument? I'll drop that
> too unless you see a reason to keep it.
>
>>>> +
>>>> +    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.

Your patch was already deeper in the stack than I was willing to
review right now (updating it and pushing implies approving everything
after it), so I sent a followup instead.

>> 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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