On 2 Jan 2014 03:59, "PJ Eby" <pje@telecommunity.com> wrote:
On Wed, Jan 1, 2014 at 9:39 AM, Nick Coghlan <ncoghlan@gmail.com> wrote:
On 1 Jan 2014 10:33, "PJ Eby" <pje@telecommunity.com> wrote:
I have only been skimming these so far, will comment more later, but I just want to mention that for standard extensions, what is the rationale for not defining e.g. commands as exports? Or for that matter, defining hooks as exports? Both commands and hooks have a payload that's the same as an export payload, i.e., a reference to an importable object. I think it'd be good for them to be defined in terms of exports in order to reduce duplication of concepts and implementations, as well as providing a PEP-defined example of how to use export groups and export names effectively.
I believe it was due to the extra layer of nesting they needed - using multiple parallel export groups with different final elements in their dotted names didn't feel right.
I guess that indicates a flaw in my initial design for the export definitions though - I agree it would be better if commands and hooks
could
be cleanly defined within the exports mechanism, rather than needing separate custom metadata extensions.
If it's a flaw, I'd say it's in my original design of entry points. ;-) Basically, I wanted a way to do -- without XML -- what Eclipse does with its "extensions" and "extension points" machinery. I went with a "flat (with dots) is better than nested" concept.
To me, though, this doesn't look terribly complicated (using entry points syntax):
[python.exports.after_install] ComfyChair.plugins = ComfyChair.plugins:install_hook
[python.exports.after_uninstall] ComfyChair.plugins = ComfyChair.plugins:install_hook
Nor this:
[python.extensions.after_install] python.exports = pip.export_group_hooks:run_install_hooks python.commands = pip.command_hook:install_wrapper_scripts
[python.extensions.after_uninstall] python.exports = pip.export_group_hooks:run_uninstall_hooks
(Also, adding hooks to *validate* extensions and exports at build and/or install time might be handy.)
Finally, note that if the typical usecase is to define *both* an install and uninstall hook, then it might be simpler to just define the hook once, as an object with 'after_install' and 'after_uninstall' methods. This avoids the need to register a hook in two groups, and in the simplest case people can just make them both module-level functions and list the module as the export.
Ah, true - people could provide them as either functions or class methods, and if we add a new one, only the list of permitted names (and their signatures) needs to change. And splitting commands into python.commands and python.commands.gui export groups would cover the export compatible cases. Since identifying "prebuilt commands" in the metadata is a new feature without any particularly compelling justification at this point, I'll likely just leave it out for 2.0. Cheers, Nick.