[PATCH] templater: do not pre-evaluate generator keyword at runsymbol (issue4868)

[Augie Fackler]

On Fri, Oct 09, 2015 at 12:42:31AM +0900, Yuya Nishihara wrote:
> # HG changeset patch
> # User Yuya Nishihara <yuya at tcha.org>
> # Date 1444314278 -32400
> #      Thu Oct 08 23:24:38 2015 +0900
> # Node ID 5103e4e21355334459cc1e5d648273eca1cd35c1
> # Parent  89b4acf69d7619220dda12fc8a9482587746310d
> templater: do not pre-evaluate generator keyword at runsymbol (issue4868)
>

queued for stable, many thanks

>
> It was introduced by e06e9fd2d99f, but the important code was removed by
> a3c2d9211294. So there was no positive effect other than exhausting memory.
>
> The problem spotted by e06e9fd2d99f is that you can't use a generator keyword
> more than once. For example, in hgweb template, "{child} {child}" doesn't work
> because the first "{child}" consumes the generator. But as a3c2d9211294 says,
> the fix was wrong because it could overwrite a callable keyword that returns
> a generator. Also the fix didn't work for a generator of generator such as
> "{diff}" keyword. So, the proper fix for that problem would be to not put
> a generator in a keyword table. Instead, it should be a factory of a generator.
>
> Note that this should fix the memory issue in hgweb, but my firefox killed by
> OOM in place. Be careful to not use a modern web browser to test the issue4868.
>
> diff --git a/mercurial/templater.py b/mercurial/templater.py
> --- a/mercurial/templater.py
> +++ b/mercurial/templater.py
> @@ -237,8 +237,6 @@ def runsymbol(context, mapping, key):
>              v = ''
>      if callable(v):
>          return v(**mapping)
> -    if isinstance(v, types.GeneratorType):
> -        v = list(v)
>      return v
>
>  def buildtemplate(exp, context):
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