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.
