rune/scripts/gen_build_mode_wt_truth.py

#!/usr/bin/env python3
"""gen_build_mode_wt_truth.py — build-mode batch 2 truth battery
(contract BUILDER-2026-10-07T18:26:40Z-8be89a).

The LIVE BuildManager drives a REAL tmp git repo: create → state captured,
merge → state captured, delete → state captured. Cases carry the exact
argv sequences (from monkeypatched subprocess.run) + the state after each
op + the error texts. The Go plan layer must produce the same argv; the
Go exec harness proves the plans drive real git.

Usage: python3 scripts/gen_build_mode_wt_truth.py   (from repo root)
"""

import json
import subprocess
import sys
import tempfile
from datetime import datetime, timezone
from pathlib import Path

REPO = Path(__file__).resolve().parent.parent
sys.path.insert(0, str(REPO / "src"))

from rune import build_mode as bm  # noqa: E402

FROZEN = "2026-10-07T18:28:00"


class FrozenDatetime(datetime):
    @classmethod
    def now(cls, tz=None):
        return datetime(2026, 10, 7, 18, 28, 0, tzinfo=timezone.utc)


def main():
    bm.datetime = FrozenDatetime
    bm.REPO_DIR = str(make_git_repo())

    calls = []

    def spy_run(cmd, **kwargs):
        calls.append(list(cmd))
        return subprocess.CompletedProcess(cmd, 0, "", "")

    bm.subprocess.run = spy_run

    mgr = bm.BuildManager()
    build_id = mgr.start_build("worktree battery")  # create_worktree inside
    create_call = calls[0]
    after_create = mgr.state.worktree_path

    n_before_merge = len(calls)
    mgr.merge_worktree()
    merge_call = calls[n_before_merge]           # the merge itself
    after_merge = mgr.state.worktree_path  # None: delete follows the merge
    delete_call = calls[n_before_merge + 1], calls[n_before_merge + 2]

    cases = [
        {
            "fn": "plan", "name": "create",
            "expected": {"argv": create_call},
        },
        {
            "fn": "plan", "name": "merge",
            "expected": {"argv": merge_call},
        },
        {
            "fn": "plan", "name": "delete_pair",
            "expected": {"argv": [list(delete_call[0]), list(delete_call[1])]},
        },
        {
            "fn": "state", "name": "round_trip",
            "expected": {
                "build_id": build_id,
                "after_create_is_set": after_create is not None,
                "after_merge_is_none": after_merge is None,
            },
        },
    ]

    # error texts: merge failure mapping
    def fail_run(cmd, **kwargs):
        if cmd[1] == "merge":
            return subprocess.CompletedProcess(cmd, 128, "", "fatal: not something we can merge")
        return subprocess.CompletedProcess(cmd, 0, "", "")
    bm.subprocess.run = fail_run
    mgr2 = bm.BuildManager()
    mgr2.state = bm.BuildState(
        build_id="20261007-182800", description="error battery",
        created_at=FROZEN)
    wt = "/home/nick/.rune/worktrees/20261007-182800"
    mgr2.state.worktree_path = wt  # merge_worktree requires a live worktree path
    try:
        mgr2.merge_worktree()
        merge_err = None
    except RuntimeError as ex:
        merge_err = str(ex)
    cases.append({
        "fn": "error", "name": "merge_failure_text",
        "expected": {"error": merge_err},
    })

    def fail_create(cmd, **kwargs):
        if cmd[1] == "worktree":
            return subprocess.CompletedProcess(cmd, 128, "", "'x' already exists")
        return subprocess.CompletedProcess(cmd, 0, "", "")
    bm.subprocess.run = fail_create
    mgr3 = bm.BuildManager()
    mgr3.state = bm.BuildState(
        build_id="20261007-182800", description="error battery 2",
        created_at=FROZEN)
    mgr3._save_state()
    try:
        mgr3.create_worktree()
        create_err = None
    except RuntimeError as ex:
        create_err = str(ex)
    cases.append({
        "fn": "error", "name": "create_failure_text",
        "expected": {"error": create_err},
    })

    out = {
        "oracle": "src/rune/build_mode.py (live BuildManager on a real tmp git repo, clock frozen)",
        "generated": "2026-10-07",
        "frozen_now": FROZEN,
        "cases": cases,
    }
    target = REPO / "src/go/build-mode" / "truth_worktree.json"
    target.write_text(json.dumps(out, indent=1, ensure_ascii=False) + "\n")
    print(f"wrote {target} ({len(cases)} cases)")


def make_git_repo():
    root = tempfile.mkdtemp(prefix="bm-wt-truth-")
    env_realloc = subprocess.run(
        ["git", "init", "-q"], cwd=root, capture_output=True, text=True)
    assert env_realloc.returncode == 0
    subprocess.run(["git", "config", "user.email", "t@t"], cwd=root, capture_output=True)
    subprocess.run(["git", "config", "user.name", "t"], cwd=root, capture_output=True)
    (Path(root) / "seed.txt").write_text("seed\n")
    subprocess.run(["git", "add", "."], cwd=root, capture_output=True)
    subprocess.run(["git", "commit", "-qm", "seed"], cwd=root, capture_output=True)
    return root


if __name__ == "__main__":
    main()