[PATCH 1 of 9 paths v2] ui: represents paths as classes

[Gregory Szorc]

I'm going to send the first "half" of this series as v3 soon. The latter
patches need a bit more work before landing. The main reason I patchbombed
such a large series initially was to show people where this was going. Now
that I think I've established that direction, I'll try to keep the patch
count down.

On Sun, Mar 1, 2015 at 1:50 PM, Gregory Szorc <gregory.szorc at gmail.com>
wrote:

> # HG changeset patch
> # User Gregory Szorc <gregory.szorc at gmail.com>
> # Date 1423341730 28800
> #      Sat Feb 07 12:42:10 2015 -0800
> # Node ID c458cf1a414e2d1534841fd55274678e93c8c707
> # Parent  7a21944731557cd18dc5c53969318d80ec547e2d
> ui: represents paths as classes
>
> Many have long wanted for paths to have expanded functionality and
> flexibility.
>
> In order to make that transition possible, we need to start
> representing paths as something more than simple strings.
>
> This patch introduces two classes:
>
> 1) "path" for representing a single path instance
> 2) "paths" for representing a collection of "paths"
>
> Since we don't like patches that introduce new code without any
> consumers, we convert ui.expandpath() to use the new APIs internally.
> Upcoming patches will start exposing "path" instances to consumers
> that currently interface with string paths.
>
> diff --git a/mercurial/ui.py b/mercurial/ui.py
> --- a/mercurial/ui.py
> +++ b/mercurial/ui.py
> @@ -5,9 +5,9 @@
>  # This software may be used and distributed according to the terms of the
>  # GNU General Public License version 2 or any later version.
>
>  from i18n import _
> -import errno, getpass, os, socket, sys, tempfile, traceback
> +import errno, getpass, os, socket, sys, tempfile, traceback, weakref
>  import config, scmutil, util, error, formatter
>  from node import hex
>
>  samplehgrcs = {
> @@ -85,8 +85,9 @@ class ui(object):
>          self._ucfg = config.config() # untrusted
>          self._trustusers = set()
>          self._trustgroups = set()
>          self.callhooks = True
> +        self.paths = paths(self)
>
>          if src:
>              self.fout = src.fout
>              self.ferr = src.ferr
> @@ -530,12 +531,12 @@ class ui(object):
>          """Return repository location relative to cwd or from [paths]"""
>          if util.hasscheme(loc) or os.path.isdir(os.path.join(loc, '.hg')):
>              return loc
>
> -        path = self.config('paths', loc)
> -        if not path and default is not None:
> -            path = self.config('paths', default)
> -        return path or loc
> +        p = self.paths.getpath(loc, default=default)
> +        if p:
> +            return p.loc
> +        return loc
>
>      def pushbuffer(self, error=False):
>          """install a buffer to capture standard output of the ui object
>
> @@ -922,4 +923,57 @@ class ui(object):
>          ui.write(s, 'label') is equivalent to
>          ui.write(ui.label(s, 'label')).
>          '''
>          return msg
> +
> +class paths(object):
> +    """Represents a collection of paths and their configs.
> +
> +    Data is derived from ui instances and the config files they have
> loaded.
> +    """
> +    def __init__(self, ui):
> +        self._uiref = weakref.ref(ui)
> +
> +    @property
> +    def ui(self):
> +        return self._uiref()
> +
> +    def __iter__(self):
> +        """Iterate all available paths, as ``path`` instances."""
> +        for name, loc in self.ui.configitems('paths'):
> +            # No URL is the same as not existing.
> +            if not loc:
> +                continue
> +            yield path(name, loc=loc)
> +
> +    def __getitem__(self, key):
> +        for path in self:
> +            if path.name == key:
> +                return path
> +        raise KeyError('path not known: %s' % key)
> +
> +    def getpath(self, name, default=None):
> +        """Return a ``path`` for the specified name.
> +
> +        Returns None if the specified path or the default path was not
> +        found.
> +        """
> +        try:
> +            return self[name]
> +        except KeyError:
> +            if default is not None:
> +                try:
> +                    return self[default]
> +                except KeyError:
> +                    pass
> +
> +        return None
> +
> +class path(object):
> +    """Represents an individual path and its configuration."""
> +
> +    def __init__(self, name, loc=None):
> +        """Construct a path from its config options."""
> +        self.name = name
> +        # We will eventually parse loc into URLs. For now, we carry the
> +        # existing API forward to make the transition simpler.
> +        self.loc = loc
>
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