Resolve wildcard classifiers in FileSet.convertible_from()

[tclose]

convertible_from() included the unresolved source types of generic converters (e.g. SetOf[T], DirectoryOf[T] in FileSet.convertible_from()). These can't be instantiated, so sourcing items through the union failed with FormatDefinitionError (seen in frametree). It also left out sources that get_converter() can actually use, e.g. Zip[TextFile] for TextFile.

Changes

• Source types with unresolved wildcard classifiers are no longer included.

• The wildcards of generic converters are resolved from the target type:

  • Zip[Compressed] → Compressed (and Tar, TarGzip): TextFile is convertible from Zip[TextFile] etc.
  • SetOf[T] → DirectoryOf[T]: DirectoryOf[TextFile] is convertible from SetOf[TextFile].
  • Compressed → Zip[Compressed]: Zip[TextFile] is convertible from TextFile.

• A resolved source is only added if get_converter() finds a converter for it. Invalid resolved types (e.g. clashing classifiers) and ones needing no conversion are skipped.

• The extras modules of generically classifiable formats (e.g. archives) are imported first, so the result doesn't depend on which extras happen to be imported already.

• Fixed WithClassifiers.register_converter checking for duplicate generic converters in a converters dict inherited from a base class (e.g. FsObject's, which can hold unclassified archive types), instead of the unclassified type's dict that the converter is stored in

Behaviour change: every format's convertible_from() now includes archives of itself (Zip[X], Tar[X], TarGzip[X]).

Tests

• New test_convertible_from_wildcards.py for the resolved cases, and checks that there are no wildcard members.
• Existing exact-union tests now check the non-generic members exactly, and that the archive members are present. Generic converters registered by other test modules made exact unions depend on test order.

[codecov]

Codecov Report

❌ Patch coverage is 84.31373% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
fileformats/core/fileset.py	85.71%	3 Missing and 4 partials ⚠️
fileformats/core/mixin.py	50.00%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!