Annotate and document compatibility.py

[knutnergaard]

@benkiel b0efc71 results in the folllowing mypy errors:

glyph.py:2903: error: Argument 1 to "list" has incompatible type "set[tuple[Optional[str], int]]"; expected "Iterable[str]"  [arg-type]
glyph.py:2908: error: Argument 1 to "list" has incompatible type "set[tuple[Optional[str], int]]"; expected "Iterable[str]"  [arg-type]
Found 2 errors in 1 file (checked 24 source files)

This can be most easily solved by casting set[tuple[Optional[str], int]] to str, but I'm not sure if that's appropriate.

Also, should this module be documented?

[codecov]

Codecov Report

❌ Patch coverage is 76.71233% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.25%. Comparing base (cdafc80) to head (bba2109).
⚠️ Report is 1 commits behind head on v1.

Files with missing lines	Patch %	Lines
Lib/fontParts/base/compatibility.py	74.24%	16 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##               v1     #822      +/-   ##
==========================================
- Coverage   76.51%   76.25%   -0.26%     
==========================================
  Files          42       42              
  Lines        6459     6558      +99     
  Branches      966      987      +21     
==========================================
+ Hits         4942     5001      +59     
- Misses       1277     1296      +19     
- Partials      240      261      +21     

Files with missing lines	Coverage Δ
Lib/fontParts/base/annotations.py	89.65% <100.00%> (+0.36%)	⬆️
Lib/fontParts/base/glyph.py	74.97% <100.00%> (-0.10%)	⬇️
Lib/fontParts/base/compatibility.py	36.68% <74.24%> (-0.24%)	⬇️

... and 19 files with indirect coverage changes

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[knutnergaard]

To clarify the mypy errors above, the confusion stems from GlyphCompatibilityReporter treating self.guidelinesMissingFromGlyph1 and self.guidelinesMissingFromGlyph2 as list[str], e.g.:

fontParts/Lib/fontParts/base/compatibility.py

Lines 415 to 421 in 84fbe94

	for name in self.guidelinesMissingFromGlyph1:
	text = self.reportDifferences(
	object1Name=self.glyph2Name,
	subObjectName="guideline",
	subObjectID=name,
	object2Name=self.glyph1Name,
	)

At the same time BaseGlyph._isConpatible is treating the same attributes as list[tuple[str | None, int]]:

fontParts/Lib/fontParts/base/glyph.py

Lines 1934 to 1947 in 84fbe94

	for source, names in ((self, selfGuidelines),
	(other, otherGuidelines)):
	for i, guideline in enumerate(source.guidelines):
	names.append((guideline.name, i))
	guidelines1 = set(selfGuidelines)
	guidelines2 = set(otherGuidelines)
	if len(guidelines1.difference(guidelines2)) != 0:
	reporter.warning = True
	reporter.guidelinesMissingFromGlyph2 = list(
	guidelines1.difference(guidelines2))
	if len(guidelines2.difference(guidelines1)) != 0:
	reporter.warning = True
	reporter.guidelinesMissingFromGlyph1 = list(
	guidelines2.difference(guidelines1))

Depending on the actual intention, one viable option to solve this is to remove the index before casting to list in BaseGlyph._isConpatible, e.g.:

reporter.guidelinesMissingFromGlyph2 = [
    name
    for name, _ in guidelines1.difference(guidelines2)
    if name is not None
    ]