[PATCH] templater: add 'env()' to fetch environment variables

[Yuya Nishihara]

On Mon, 16 Jan 2017 22:28:17 -0500, Matt Harbison wrote:
> On Mon, 16 Jan 2017 07:25:24 -0500, Yuya Nishihara <yuya at tcha.org> wrote:
> > This can be a simple {env} (or {environ}) keyword and you can use get()
> > function, e.g. {get(env, 'pattern')}. showextras() is a good example of
> > building template dict.
> 
> I've got to be missing something simple.  I added this code:
> 
> @templatekeyword('environ')
> def showenviron(**args):
>      """A dictionary of environment variables."""
> 
>      env = encoding.environ
>      env = util.sortdict((k, env[k]) for k in sorted(env))
>      makemap = lambda k: {'key': k, 'value': env[k]}
>      c = [makemap(k) for k in env]
>      f = _showlist('environ', c, **args)
>      return _hybrid(f, env, makemap,
>                     lambda x: '%s=%s' % (x['key'], x['value']))
> 
> And these forms work:
> 
> $ pattern=foo ../hg log -r . -T "{get(environ, 'PATTERN')}"
> foo
> $ pattern=foo ../hg log -r . -T "{environ % '{key} -> {value}\n'}"
> !:: -> ::\
> ALLUSERSPROFILE -> C:\ProgramData
> ...
> 
> But this doesn't.  It spews a wall of text that looks like templater  
> internals:
> 
> $ pattern=foo ../hg log -r . -T "{environ}"
> filestermwidthnamespacesrevcachetroublesobsoleteactivebookmarkdatep1nodebookmarks...
> 
> The {extras} template that I copy/pasted from lists key=value lines.  I
> also looked at 'namespaces', but couldn't figure out what triggered this.

The bare {extras} is rendered by _showlist() as an old-style template, and
it appears _showlist() can't process dict values if no template provided.
(It somehow yields a dict of full args.)

https://www.mercurial-scm.org/repo/hg/file/4.0.2/mercurial/templatekw.py#l89

One way to avoid spilling out the internal variables is to set the default
'environ' template.

https://www.mercurial-scm.org/repo/hg/file/4.0.2/mercurial/cmdutil.py#l1507

Another problem is the 'environ' keyword conflict with the 'environ' template.
We'll have to pick a plural name (e.g. 'envs', 'environs', 'envvars'.)