chore: import upstream snapshot with attribution

.github/scripts/pr-size/compute_label.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+"""Compute a ``size/{XS,S,M,L,XL}`` label for a PR from its changed files.
+
+Reads the GitHub ``pulls/{n}/files`` JSON array on stdin (objects with
+``filename``, ``additions``, ``deletions``) and prints the size label. Lock
+and generated files are excluded so a dependency bump does not inflate the
+size. Pure stdlib so it runs without an install and is unit-tested directly.
+"""
+
+from __future__ import annotations
+
+import json
+import re
+import sys
+
+# Files whose churn should not count toward review size.
+GENERATED = (
+    re.compile(r"^uv\.lock$"),
+    re.compile(r"(^|/)package-lock\.json$"),
+    re.compile(r"(^|/)yarn\.lock$"),
+)
+
+# Upper bound (inclusive) of changed lines for each label, smallest first.
+THRESHOLDS = (
+    ("XS", 9),
+    ("S", 49),
+    ("M", 199),
+    ("L", 499),
+    ("XL", float("inf")),
+)
+
+
+def is_generated(filename: str) -> bool:
+    return any(p.search(filename) for p in GENERATED)
+
+
+def size_label(total: int) -> str:
+    for name, upper in THRESHOLDS:
+        if total <= upper:
+            return f"size/{name}"
+    raise AssertionError("THRESHOLDS must end with an unbounded bucket")
+
+
+def total_changes(files: list[dict]) -> int:
+    return sum(
+        f.get("additions", 0) + f.get("deletions", 0)
+        for f in files
+        if not is_generated(f.get("filename", ""))
+    )
+
+
+def main() -> int:
+    files = json.load(sys.stdin)
+    print(size_label(total_changes(files)))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())