Align t-string/bytes mix error with CPython 3.14 - #27766

import ast
import itertools
import os
import pathlib
import subprocess

RUFF = pathlib.Path(os.environ("RUFF_REPO")) / "/target/debug/ruff"

KINDS = {
    "S": "'{}'",
    "B": "b'{}'",
    "F": "f'{}'",
    "T": "t'{}'",
}


def build_source(combo):
    parts = [KINDS[k].format(chr(ord("a") + i)) for i, k in enumerate(combo)]
    return " ".join(parts)


def cpython_classify(source):
    try:
        ast.parse(source)
        return "ok"
    except SyntaxError as e:
        msg = str(e.msg)
        if "bytes and nonbytes" in msg:
            return "bytes"
        if "t-string" in msg:
            return "tstring"
        return f"other:{msg}"


def ruff_classify(source):
    proc = subprocess.run(
        [RUFF, "check", "--target-version", "py314", "--no-cache", "--isolated", "-"],
        input=source,
        capture_output=True,
        text=True,
    )
    out = proc.stdout + proc.stderr
    has_bytes = "Bytes literal cannot be mixed" in out
    has_tstring = "Cannot mix t-string literals" in out
    if has_bytes and has_tstring:
        return "both!"
    if has_bytes:
        return "bytes"
    if has_tstring:
        return "tstring"
    # Ignore unrelated diagnostics (e.g. B018/B021 lint noise) - we only care
    # about whether the two string-mixing syntax errors are reported correctly.
    return "ok"


def main():
    mismatches = []
    total = 0
    for length in (2, 3, 4, 5):
        for combo in itertools.product("SBFT", repeat=length):
            total += 1
            source = build_source(combo)
            cpy = cpython_classify(source)
            ruf = ruff_classify(source)
            if cpy != ruf:
                mismatches.append((combo, source, cpy, ruf))

    print(f"Checked {total} combinations (lengths 2-4 over S/B/F/T)")
    print(f"Mismatches: {len(mismatches)}")
    for combo, source, cpy, ruf in mismatches:
        print(f"  {''.join(combo):6} {source!r:45} cpython={cpy!r:12} ruff={ruf!r}")


if __name__ == "__main__":
    main()