Add script to shrink all formatter errors (#5943)

**Summary** Add script to shrink all formatter errors: This started as a
fun idea and turned out really useful: This script gives us a single
Python file with all formatter stability errors. I want to keep it
around to occasionally update #5828 so I added it to the git.

**Test Plan** None, this is a helper script

crates/ruff_python_formatter/shrink_formatter_errors.py

@@ -0,0 +1,75 @@
+"""Take `format-dev --stability-check` output and shrink all stability errors into a
+single Python file. Used to update https://github.com/astral-sh/ruff/issues/5828 ."""
+
+from __future__ import annotations
+
+import json
+import os
+from concurrent.futures import ThreadPoolExecutor, as_completed
+from pathlib import Path
+from subprocess import check_output
+from tempfile import NamedTemporaryFile
+
+from tqdm import tqdm
+
+root = Path(
+ check_output(["git", "rev-parse", "--show-toplevel"], text=True).strip(),
+)
+target = root.joinpath("target")
+
+error_report = target.joinpath("formatter-ecosystem-errors.txt")
+error_lines_prefix = "Unstable formatting "
+
+
+def get_filenames() -> list[str]:
+ files = []
+ for line in error_report.read_text().splitlines():
+ if not line.startswith(error_lines_prefix):
+ continue
+ files.append(line.removeprefix(error_lines_prefix))
+ return files
+
+
+def shrink_file(file: str) -> tuple[str, str]:
+ """Returns filename and minimization"""
+ with NamedTemporaryFile(suffix=".py") as temp_file:
+ print(f"Starting {file}")
+ ruff_dev = target.joinpath("release").joinpath("ruff_dev")
+ check_output(
+ [
+ target.joinpath("release").joinpath("ruff_shrinking"),
+ file,
+ temp_file.name,
+ "Unstable formatting",
+ f"{ruff_dev} format-dev --stability-check {temp_file.name}",
+ ],
+ )
+ print(f"Finished {file}")
+ return file, Path(temp_file.name).read_text()
+
+
+def main():
+ storage = target.joinpath("minimizations.json")
+ output_file = target.joinpath("minimizations.py")
+ if storage.is_file():
+ outputs = json.loads(storage.read_text())
+ else:
+ outputs = {}
+ files = sorted(set(get_filenames()) - set(outputs))
+ # Each process will saturate one core
+ with ThreadPoolExecutor(max_workers=os.cpu_count()) as executor:
+ tasks = [executor.submit(shrink_file, file) for file in files]
+ for future in tqdm(as_completed(tasks), total=len(files)):
+ file, output = future.result()
+ outputs[file] = output
+ storage.write_text(json.dumps(outputs, indent=4))
+
+ # Write to one shareable python file
+ with output_file.open("w") as formatted:
+ for file, code in sorted(json.loads(storage.read_text()).items()):
+ file = file.split("/target/checkouts/")[1]
+ formatted.write(f"# {file}\n{code}\n")
+
+
+if __name__ == "__main__":
+ main()