diff mercurial/formatter.py @ 36445:e8d37838f5df

templatekw: add 'requires' flag to switch to exception-safe interface

The current templatekw interface, f(repo, ctx, templ, **args), is horrible
because it's quite easy to encounter TypeError, ValueError, etc. It's also
bad for Python 3 porting due to the **kwargs issue.

This patch introduces a flag to switch to new f(context, mapping) API seen
in templater functions. The requirement spec isn't verified (yet) because
context.resource() can gracefully raise a ResourceUnavailable exception,
but it's planned to be used as a filter in the help, such as "Revision
Keywords" (if 'ctx' in requires), "File Keywords" (if 'fctx' in requires),
etc.

showauthor() is ported to the new API as an example. 20 more follows.

--- a/mercurial/formatter.py	Sun Feb 25 12:50:30 2018 +0900
+++ b/mercurial/formatter.py	Sun Feb 25 13:24:35 2018 +0900
@@ -383,9 +383,7 @@
             return
         ref = self._parts[part]
 
-        # TODO: add support for filectx. probably each template keyword or
-        # function will have to declare dependent resources. e.g.
-        # @templatekeyword(..., requires=('ctx',))
+        # TODO: add support for filectx
         props = {}
         # explicitly-defined fields precede templatekw
         props.update(item)