Test parsing/writing of .glyphs files with glyphsLib master vs 'classtree' branch

roundtrip.py

#!/usr/bin/env python
from __future__ import print_function
import sys
import os
from fontTools.misc.py23 import open, StringIO, tounicode, tostr
import difflib

from glyphsLib import loads

try:
    # 'GlyphsWriter' is only present on 'classtree' branch
    from glyphsLib.writer import GlyphsWriter
    ON_CLASSTREE_BRANCH = True
except ImportError:
    ON_CLASSTREE_BRANCH = False


def roundtrip_master(path):
    from glyphsLib import dump

    with open(path, 'r', encoding='utf-8') as f:
        input_data = f.read()

    s = StringIO()
    dump(loads(input_data), s)
    output_data = s.getvalue()

    actual = tounicode(output_data, 'utf-8').splitlines(True)
    expected = input_data.splitlines(True)

    return expected, actual


def roundtrip_classtree(path):
    with open(path, 'r', encoding='utf-8') as f:
        input_data = f.read()

    s = StringIO()
    w = GlyphsWriter(fp=s)
    # XXX can't use `GlyphsWriter.write`  as it closes the file
    w.writeDict(loads(input_data))
    s.write(tostr("\n"))
    output_data = s.getvalue()

    actual = tounicode(output_data, 'utf-8').splitlines(True)
    expected = input_data.splitlines(True)

    return expected, actual


def diff_roundtrip(path):
    name = os.path.basename(path)

    if ON_CLASSTREE_BRANCH:
        expected, actual = roundtrip_classtree(path)
    else:
        expected, actual = roundtrip_master(path)

    if actual != expected:
        for line in difflib.unified_diff(
                expected, actual,
                fromfile="%s <input>" % name,
                tofile="%s <roundtripped>" % name):
            print(line, end="")
        return 1
    return 0


def main():
    files = sys.argv[1:]
    if not files:
        print("./roundtrip.py file [file ...]")
        return 1

    rv = 0
    for i, path in enumerate(files):
        if i > 0:
            print("\n======\n")
        rv |= diff_roundtrip(path)

    return rv


if __name__ == "__main__":
    sys.exit(main())