Internet radio browser GUI for music/video streams from various directory services.

⌈⌋ branch:  streamtuner2

Update of "plugin meta data"


Artifact ID: cb4b8fe350077e3472fc349c56616937c6f3f858
Page Name:plugin meta data
Date: 2015-04-27 21:32:25
Original User: mario
Parent: 61c4af8632af026c52ac000b977198a557578942 (diff)
Next 478ea535493535266c5011e51f44a5cfe3298776

Plugin meta spec

Streamtuner2 now uses a proper plugin description scheme. Note that this is completely unrelated to the streamtuner2 or channels API, or how plugins are actually initialized (pkgutil, imp, implib, pluginbase/plugnplay).

Basically the top-level comment block is scanned on initialization. It simply lists a few key: values for documentation and technical descriptors. It's basically a subset of YAML embedded in a script comment.

# api: streamtuner2
# type: feature
# title: My Plugin
# description: Lists all the things
# version: 1.0
# category: music
# config: { name: myconf, value: 1, type: boolean, description: enable foo }
# And here goes a longer doc/comment.

The key names are case-insensitive of course. A few fields like title:, description: are required. Theoretically also the api: and type:. Though in ST2 they're currently just used for decorative purposes like the category: or version: field.

More interestingly the config: field can be used to describe plugin options. Default values will automatically end up in streamtuners conf.* dict, and are presented to users in the config dialog.

  • A value: represents the default.
  • The type: select can be used for dropdown boxes, with a select: key=VAl|key2=VAL2.. attribute for options.
  • Other type: values are interpreted as strings, except type: boolean which becomes a checkbox.
  • A per-option category: attribute is ignored at the moment.
  • Params can be optionally quoted as in value: "Desc, desc, desc." in case they contain commas (which otherwise separate option attrs.)

And of course, the config: field can list multiple options. Simply make it multi-line (every plugin meta field can be) by indenting wrapped lines.


This scheme is designed to be language-agnostic. It originated in PHP way back (see libconfig), precisely to avoid a few common misdesigns.

  • Meta data does not belong in code.
    Because that incurs always importing them, even when they may go uninitialized/unused.

  • And it certainly should not reside in externalized ini/json data blobs.
    (Or do you want ants? Because that's how you get ants.)

  • Furthermore it encourages a useful documentation block atop.
    (Instead of license blobs everywhere in lieu of proper comments.)

The meta description block incidentally can also serve as packaging control scheme. The pack: descriptor is used by fpm/xpm -s src. Which avoids manually doubling descriptions into separated as the current Python packaging eco system does.
Note though that the plugin description scheme is primarily intended for in-application feature/plugin management. Reducing packaging effort is just a by-effect.

argparse config: struct

Similarly to internal plugin configuration settings, the config: list is now used for ArgumentParser definitions. Fields are slightly remapped to remain in line with regular options.

# config:
#  { arg: -D, name: debug, type: bool, description: enable debugging }
#  { arg: -e, name: enable[], type: str*, description: add plugin }

It's basically just the extra arg: field which discerns such entries from standard options. And the type: may carry an optional quantifier (mapped to argparses' nargs= flag). Or the name: can indicate a list property with [] attached (maps to argparses' append instead of store). Not every argparse peculiarity is provided for though. And using a docopt section would probably be a better option anyway.