This lets index-v1 be parsed directly into class instances because the
field/instance var names match exactly. The original index v0 element
must retain the 'lastupdated' name for backwards compatibility.
Like with the App class in the commit before, this makes it a lot
easier to work with this data when converting between the internal
formats and external formats like YAML, JSON, MsgPack, protobuf, etc.
The one unfortunate thing here is Build.update. It becomes
dict.update(), which is a method not an attribute.
build.get('update') or build['update'] could be used, but that would
be oddly inconsistent. So instead the field is renamed to
'androidupdate', except for in the .txt v0 metadata files. This better
describes what field does anyway, since it runs `android update`.
Build.update is only referenced in two places right next to each other
for the ant builds, so this change still seems worthwhile.
Python is heavily based on its core data types, and dict is one of the more
important ones. Even classes are basically a wrapper around a dict. This
converts metadata.App to be a subclass of dict so it can behave like a dict
when being dumped and loaded. This makes its drastically easier to use
different data formats for build metadata and for sending data to the
client. This approach will ultimately mean we no longer have to maintain
custom parsing and dumping code.
This also means then that the YAML/JSON field names will not have spaces in
them, and they will match exactly what it used as the dict keys once the
data is parsed, as well as matching exactly the instance attribute names:
* CurrentVersion: 1.2.6
* app['CurrentVersion'] == '1.2.6'
* app.CurrentVersion == '1.2.6'
Inspired by:
https://goodcode.io/articles/python-dict-object/
When making code changes related to the metadata parsing, it is useful to
see how the internal format has changed by seeing the differences in the
dump files. Those files are currently in the binary .pickle format. This
just straight converts them to YAML, which is a text format, so that normal
diff tools work to see changes.
The dump files are named .yaml instead of .yml since .yml is used for hand-
edited YAML files for fdroiddata/metadata, while these dump files here are
a human readable form of a Python pickle.
