[PATCH] ui: remove urllib2 from being imported early

[Augie Fackler]

On Tue, Feb 14, 2017 at 10:15:10AM -0800, Kyle Lippincott via Mercurial-devel wrote:
> # HG changeset patch
> # User Kyle Lippincott <spectral at google.com>
> # Date 1486897598 28800
> #      Sun Feb 12 03:06:38 2017 -0800
> # Node ID 1f3234760225170767d10bfcd9cc5b2431b65471
> # Parent  72f25e17af9d6a206ea374c30f229ae9513f3f23
> ui: remove urllib2 from being imported early

Queued, thanks for fighting the good fight on startup time.

>
> Before this change, urllib2 was brought in when constructing the ui object, and
> that added ~5ms on my Linux workstation to the hg startup time for every
> command, bringing the time for 'HGRCPATH=/dev/null hg root' from 46ms to 40ms.
>
> Now, we construct a single proxy object per initial ui creation (so that if the
> ui is copied they share the object), but defer the actual instantiation of it
> and the import of urllib2 until it's needed.
>
> diff -r 72f25e17af9d -r 1f3234760225 mercurial/ui.py
> --- a/mercurial/ui.py	Mon Feb 13 02:31:56 2017 -0800
> +++ b/mercurial/ui.py	Sun Feb 12 03:06:38 2017 -0800
> @@ -94,6 +94,24 @@
>  # pager =""",
>  }
>
> +
> +class httppasswordmgrdbproxy(object):
> +    """Delays loading urllib2 until it's needed."""
> +    def __init__(self):
> +        self._mgr = None
> +
> +    def _get_mgr(self):
> +        if self._mgr is None:
> +            self._mgr = urlreq.httppasswordmgrwithdefaultrealm()
> +        return self._mgr
> +
> +    def add_password(self, *args, **kwargs):
> +        return self._get_mgr().add_password(*args, **kwargs)
> +
> +    def find_user_password(self, *args, **kwargs):
> +        return self._get_mgr().find_user_password(*args, **kwargs)
> +
> +
>  class ui(object):
>      def __init__(self, src=None):
>          """Create a fresh new ui object if no src given
> @@ -145,7 +163,7 @@
>              # shared read-only environment
>              self.environ = encoding.environ
>
> -            self.httppasswordmgrdb = urlreq.httppasswordmgrwithdefaultrealm()
> +            self.httppasswordmgrdb = httppasswordmgrdbproxy()
>
>          allowed = self.configlist('experimental', 'exportableenviron')
>          if '*' in allowed:
> @@ -172,7 +190,7 @@
>          """Clear internal state that shouldn't persist across commands"""
>          if self._progbar:
>              self._progbar.resetstate()  # reset last-print time of progress bar
> -        self.httppasswordmgrdb = urlreq.httppasswordmgrwithdefaultrealm()
> +        self.httppasswordmgrdb = httppasswordmgrdbproxy()
>
>      def formatter(self, topic, opts):
>          return formatter.formatter(self, topic, opts)
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