WebKitLibraries/AvailabilityOverlay/generate-overlay.py

#!/usr/bin/env python3
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"""Generate a clang VFS overlay YAML that swaps the SDK's
<os/availability.h> and <Availability.h> for WebKit-supplied stubs that
defuse availability checks.
"""

import argparse
import json
import sys
from pathlib import Path

ap = argparse.ArgumentParser(description=__doc__)
ap.add_argument("--sdk", type=Path, required=True)
ap.add_argument("--stubs", type=Path, required=True)
ap.add_argument("--out", type=Path, required=True)
args = ap.parse_args()

HEADERS = ("usr/include/os/availability.h", "usr/include/Availability.h")

content = json.dumps({
    "version": 0,
    "case-sensitive": False,
    "roots": [
        {"name": str(args.sdk / rel),
         "type": "file",
         "external-contents": str(args.stubs / rel)}
        for rel in HEADERS
    ],
}, indent=2) + "\n"

# Skip the write when content is unchanged to preserve mtime and avoid
# spurious downstream rebuilds. Writing directly (rather than temp+rename)
# is required for Xcode's user-script sandbox, which only permits writes
# to declared outputPaths.
if args.out.is_file() and args.out.read_text() == content:
    sys.exit(0)
args.out.write_text(content)