[PATCH] extensions: ignore invalid extensions completely when listing disabled commands

[Brodie Rao]

On Dec 19, 2010, at 7:00 AM, Mads Kiilerich wrote:

> # HG changeset patch
> # User Mads Kiilerich <mads at kiilerich.com>
> # Date 1292697155 -3600
> # Node ID ad1938c4715bdc6601ab35902fde2db4aec0aa2d
> # Parent  115a9760c38222ee01fabea6904c6bf1956d6f12
> extensions: ignore invalid extensions completely when listing  
> disabled commands
>
> Invalid extensions in hgext/ could in some cases cause a crash when  
> searching
> for unknown commands in disabled extensions.
>
> This makes us silently ignore all errors when trying to extract  
> commands from
> extensions. Extensions might have been disabled for a reason and we  
> don't care
> bout any errors until they are enabled.
>
> Reported on https://bugzilla.redhat.com/show_bug.cgi?id=663183 with  
> forest.py.

My rationale for not silencing exceptions in this feature was that  
hgext should never have extensions that can't be imported or can't  
have commands safely extracted.

Installing third party extensions into hgext seems like the wrong  
thing to do, in my opinion. In spite of this, swallowing those  
exceptions is probably okay as long as hg tells us what extension  
failed and gives us the traceback if we specify --traceback.

> diff --git a/mercurial/extensions.py b/mercurial/extensions.py
> --- a/mercurial/extensions.py
> +++ b/mercurial/extensions.py
> @@ -264,7 +264,7 @@
>         try:
>             aliases, entry = cmdutil.findcmd(cmd,
>                 getattr(mod, 'cmdtable', {}), strict)
> -        except (error.AmbiguousCommand, error.UnknownCommand):
> +        except:
>             return

We should probably use except Exception: instead of except:. I don't  
think we want to catch SystemExit or KeyboardInterrupt here.

I'd leave the original except clause in, add a second one for  
Exception that prints a debug message or a warning that we couldn't  
introspect the disabled extension, and call ui.traceback() after that.

>         for c in aliases:
>             if c.startswith(cmd):
> diff --git a/tests/test-extension.t b/tests/test-extension.t
> --- a/tests/test-extension.t
> +++ b/tests/test-extension.t
> @@ -303,6 +303,9 @@
>   $ cat > hgext/broken.py <<EOF
>> "broken extension'
>> EOF
> +  $ cat > hgext/forest.py <<EOF
> +  > cmdtable = None
> +  > EOF
>   $ cat > path.py <<EOF
>> import os, sys
>> sys.path.insert(0, os.environ['HGEXTPATH'])