Rename glyph names in OpenType feature files

rename_fea_glyphs.py

from functools import singledispatch
from io import StringIO

from fontTools.feaLib import ast
from fontTools.feaLib.error import FeatureLibError
from fontTools.feaLib.parser import Parser


def renameGlyphs(feaSource, renameFunc, glyphNames=()):
    features = Parser(StringIO(feaSource), glyphNames=glyphNames).parse()

    renameStatement(features, renameFunc)

    return features.asFea()


@singledispatch
def renameStatement(statement, renameFunc):
    if not hasattr(statement, "__dict__"):
        return

    for value in statement.__dict__.values():
        renameStatement(value, renameFunc)


@renameStatement.register
def _(statement: list | tuple, renameFunc):
    for st in statement:
        renameStatement(st, renameFunc)


@renameStatement.register
def _(
    statement: ast.LanguageSystemStatement | ast.Comment | ast.FeatureLibLocation,
    renameFunc,
):
    pass


@renameStatement.register
def _(statement: ast.GlyphClass, renameFunc):
    if hasattr(statement, "_has_been_renamed"):
        return
    statement._has_been_renamed = True
    statement.glyphs = [renameFunc(g) for g in statement.glyphs]
    statement.original = [
        (renameFunc(start), renameFunc(end)) for start, end in statement.original
    ]


@renameStatement.register
def _(statement: ast.GlyphName, renameFunc):
    if hasattr(statement, "_has_been_renamed"):
        return
    statement._has_been_renamed = True
    statement.glyph = renameFunc(statement.glyph)


@renameStatement.register
def _(statement: ast.LigatureSubstStatement, renameFunc):
    if hasattr(statement, "_has_been_renamed"):
        return
    statement._has_been_renamed = True
    renameStatement(statement.prefix, renameFunc)
    renameStatement(statement.glyphs, renameFunc)
    renameStatement(statement.suffix, renameFunc)
    if isinstance(statement.replacement, str):
        statement.replacement = renameFunc(statement.replacement)
    else:
        renameStatement(statement.replacement, renameFunc)


@renameStatement.register
def _(statement: ast.MarkClass, renameFunc):
    # Skip, MarkClassDefinition deals with this?
    # Else we'll get RecursionError: maximum recursion depth exceeded
    pass


if __name__ == "__main__":
    import sys

    def renameFunc(gn):
        assert not gn.endswith(".XXX"), gn
        return gn + ".XXX"

    for p in sys.argv[1:]:
        print("#", p)

        with open(p) as f:
            feaSource = f.read()

        try:
            newFea = renameGlyphs(feaSource, renameFunc)
        except FeatureLibError as e:
            print("**************** FeatureLibError", e)

        print(newFea)