strip unused <symbol> elements in noto-emoji svgs

remove_unused_symbols.py

import sys
import glob
from lxml import etree

svg_directory = sys.argv[1]

noid_files = set()
id_files = set()
for filename in glob.glob(f"{svg_directory}/*.svg"):
    tree = etree.parse(filename)
    svg = tree.getroot()
    for symbol in svg.xpath(
        ".//svg:symbol", namespaces={"svg": "http://www.w3.org/2000/svg"}
    ):
        if "id" not in symbol.attrib:
            symbol.getparent().remove(symbol)
            noid_files.add(filename)

            with open(filename, "wb") as fp:
                fp.write(etree.tostring(tree))
        else:
            id_files.add(filename)

print(f"Files containing <symbol> without 'id' attribute: {len(noid_files)}")
print(noid_files)
print()
print(f"Files containing <symbol> with 'id' attribute: {len(id_files)}")
print(id_files)