As Martin Hosken reported in https://github.com/fonttools/fonttools/pull/1096,
feaLib currently incorrectly handles the case where a marked input
glyph sequence in a contextual chaining sub/pos rule is split into
multiple runs, rather than being a single continuous run of ' marked
glyphs.
The consensus there was to raise a syntax error like makeotf instead of
second-guessing and silently fixing it like fontforge does.
... instead of a glyphMap dict.
The parser does not actually need a reverse glyph order mapping as
it is not interested in knowing the glyphID from the glyph name,
but only whether a glyph is in the font or not.
This makes it easier for client code (e.g. ufo2ft feature compiler)
to use the feaLib Parser, without having to first construct and pass
it a glyphMap argument.
Before this change, the following glyph class:
@Vowels = [@Vowels.lc @Vowels.uc y Y];
Would be written back as:
@Vowels = [@Vowels.lc = [a e i o u]; @Vowels.uc = [A E I O U]; y Y];
Which is clearly invalid. It seems for GlyphClass.asFea() to work
correctly here we should be using GlyphClassName not GlyphClass
for the nested classes (similar to the code at the beginning of
parse_glyphclass_()).
The syntax tree representation now reflects the syntax of feature files.
Before this change, FeatureNames did not have their own `ast.Block`,
which had made the code quite messy.
Before this change, some table statements would allow empty statements
(just a semicolon) while others would not allow them. After this change,
we're more consistent.
We now correctly handle nameid statements with surrogate pairs and
old-style macOS-encoded names (provided that fonttools supports the
specified encoding).
Resolves https://github.com/fonttools/fonttools/issues/842.
