Use warnings.pm to calculate warnings tree

[haarg]

This removes the hard coded warnings tree information, and instead uses the %Bits variable from warnings.pm to check what warnings categories belong to each other. This ensures that the categories are up to date with the perl version installed, and removes the need for Tree::DAG_Node as a prerequisite.

Although %Bits isn't a documented part of the warnings API, it has existed with the same structure since lexical warnings were introduced. This patch also doesn't depend any specific values in %Bits, so it should be safe across perl versions.

This also remove removes the $Test::Warn::Categorization:tree variable. Although it was documented, it was discouraged and was never used on CPAN.

[ribasushi]

+1. @haarg: excellent work!

[ribasushi]

Another reason to accept this pull request: Regardless of Tree::DAG_Node and its dependencies getting fxed to work on 5.8, Tree::DAG_Node irrevocably went 5.8.1 in order to support some unicode thingymajig. The rest of Test::Warn remains fully compatible with 5.6 however. This pull request will keep it that way.

Cheers

[haarg]

@chorny Did you ever get around to looking at this?

[ribasushi]

@chorny Poke poke. I am strongly urging you to look into releasing this: Tree::DAG_Node went all modern and depends on a lot of CPAN, making T::W rather very heavy. In addition it depends on utter crap like File::Slurp, which does not even install under HARNESS_OPTIONS=jX

Cheers

[ribasushi]

Added a related RT issue, sorry for the spam in advance, but the dependency on File::Slurp (among other things) continues being a problem, and there has been no response of any kind.

https://rt.cpan.org/Ticket/Display.html?id=92293

[chorny]

Note: I'm not original author of this module, and there are places of this module which I don't know.

After studying code, I found out there is really no code for checking warnings in categories. There are no tests that check how Test::Warn works with categories. Check is done only for qr/category_name/. In some case this works, like for category 'uninitialized'. For 'utf8' it does not work. Perl does not have a list of warnings, so it is not possible to generate one for Test::Warn. It only can be done manually. It may be easier to write warning extractor for Perl source (did not studied yet if it is possible), but still it can't be fully automated.

So I see 2 possibilities:

1. Drop warning categories from Test::Warn. I don't think that is a good solution.
2. Add warnings to categories by request.

[karenetheridge]

On Sat, Jan 25, 2014 at 01:40:34PM -0800, Alexandr Ciornii wrote:

1. Drop warning categories from Test::Warn. I don't think that is a good solution.

If they don't work in the first place, then at least this would be honest.

[haarg]

The warning category support is certainly limited and flawed, but many modules are already using it. Documenting its limitations would certainly be good, but I don't think removing it is reasonable.

This PR doesn't cause any problems that don't already exist. The existing warning tree baked into the module is just matching against the warning categories as well. Manually maintaining that list adds no value, because it is just a copy anyway.

So I still favor merging this, and probably adding a note about the limitations of the warning category support. Improving the category matching to work more accurately can be addressed separately.