test_commit_concurrent_ref_safety.py
python
sha256:f6cd81bc71702f5c1c6890bd39aaba994fe58c75f019d7c03934724fa2739bb4
fix: carry dev changes harmony dropped in merge — detached …
Sonnet 4.6
minor
⚠ breaking
16 days ago
| 1 | """Concurrent ref-update safety for muse commit. |
| 2 | |
| 3 | Before this fix, write_branch_ref was an unconditional overwrite. |
| 4 | Two agents committing to the same branch simultaneously would silently |
| 5 | orphan one commit — the second write_branch_ref call would overwrite |
| 6 | the first with no detection, dropping a commit from the branch history. |
| 7 | |
| 8 | Fix: |
| 9 | write_branch_ref gains an optional expected_id parameter. When |
| 10 | provided, the write only proceeds if the current ref value matches. |
| 11 | If it doesn't match (another agent advanced the ref first), it raises |
| 12 | RefConflictError with a clear message. |
| 13 | |
| 14 | commit passes parent_id as expected_id so any concurrent advance of |
| 15 | the branch ref between the parent_id read and the ref write is caught |
| 16 | and reported as a retryable error rather than silently overwriting. |
| 17 | |
| 18 | Test structure: |
| 19 | Tier 1 — write_branch_ref CAS unit tests |
| 20 | Tier 2 — commit detects branch-moved condition |
| 21 | Tier 3 — concurrent commit threads: only one succeeds per slot |
| 22 | """ |
| 23 | |
| 24 | from __future__ import annotations |
| 25 | |
| 26 | import pathlib |
| 27 | import threading |
| 28 | from typing import TYPE_CHECKING |
| 29 | |
| 30 | import pytest |
| 31 | |
| 32 | from muse.core.refs import write_branch_ref |
| 33 | from muse.core.types import fake_id |
| 34 | from muse.core.paths import heads_dir, muse_dir |
| 35 | from tests.cli_test_helper import CliRunner, InvokeResult |
| 36 | |
| 37 | if TYPE_CHECKING: |
| 38 | pass |
| 39 | |
| 40 | runner = CliRunner() |
| 41 | |
| 42 | |
| 43 | def _run(repo: pathlib.Path, *args: str) -> None: |
| 44 | r = runner.invoke(None, list(args), cwd=repo) |
| 45 | assert r.exit_code == 0, f"muse {' '.join(args)} failed:\n{r.output}" |
| 46 | |
| 47 | |
| 48 | def _try(repo: pathlib.Path, *args: str) -> InvokeResult: |
| 49 | return runner.invoke(None, list(args), cwd=repo) |
| 50 | |
| 51 | |
| 52 | def _make_bare_refs(tmp_path: pathlib.Path) -> pathlib.Path: |
| 53 | """Minimal .muse/refs/heads/ tree — enough for write_branch_ref.""" |
| 54 | import json |
| 55 | muse = muse_dir(tmp_path) |
| 56 | for d in ("objects", "commits", "snapshots", "refs/heads"): |
| 57 | (muse / d).mkdir(parents=True, exist_ok=True) |
| 58 | (muse / "repo.json").write_text(json.dumps({"repo_id": "test-repo"})) |
| 59 | (muse / "HEAD").write_text("ref: refs/heads/main\n") |
| 60 | return tmp_path |
| 61 | |
| 62 | |
| 63 | # --------------------------------------------------------------------------- |
| 64 | # Tier 1 — write_branch_ref CAS unit tests |
| 65 | # --------------------------------------------------------------------------- |
| 66 | |
| 67 | |
| 68 | class TestWriteBranchRefCAS: |
| 69 | def test_unconditional_write_succeeds(self, tmp_path: pathlib.Path) -> None: |
| 70 | repo = _make_bare_refs(tmp_path) |
| 71 | id_a = fake_id("a") |
| 72 | write_branch_ref(repo, "main", id_a) |
| 73 | ref = (heads_dir(repo) / "main").read_text().strip() |
| 74 | assert ref == id_a |
| 75 | |
| 76 | def test_cas_succeeds_when_expected_matches(self, tmp_path: pathlib.Path) -> None: |
| 77 | repo = _make_bare_refs(tmp_path) |
| 78 | id_a = fake_id("a") |
| 79 | id_b = fake_id("b") |
| 80 | write_branch_ref(repo, "main", id_a) |
| 81 | write_branch_ref(repo, "main", id_b, expected_id=id_a) |
| 82 | ref = (heads_dir(repo) / "main").read_text().strip() |
| 83 | assert ref == id_b |
| 84 | |
| 85 | def test_cas_fails_when_expected_does_not_match(self, tmp_path: pathlib.Path) -> None: |
| 86 | from muse.core.refs import RefConflictError |
| 87 | repo = _make_bare_refs(tmp_path) |
| 88 | id_a = fake_id("a") |
| 89 | id_b = fake_id("b") |
| 90 | id_c = fake_id("c") |
| 91 | write_branch_ref(repo, "main", id_a) |
| 92 | with pytest.raises(RefConflictError): |
| 93 | write_branch_ref(repo, "main", id_c, expected_id=id_b) |
| 94 | # ref must be unchanged |
| 95 | ref = (heads_dir(repo) / "main").read_text().strip() |
| 96 | assert ref == id_a |
| 97 | |
| 98 | def test_cas_fails_when_ref_is_missing_and_expected_is_set(self, tmp_path: pathlib.Path) -> None: |
| 99 | from muse.core.refs import RefConflictError |
| 100 | repo = _make_bare_refs(tmp_path) |
| 101 | id_a = fake_id("a") |
| 102 | id_b = fake_id("b") |
| 103 | # No ref written yet — expected_id=id_a should fail (ref is None, not id_a) |
| 104 | with pytest.raises(RefConflictError): |
| 105 | write_branch_ref(repo, "main", id_b, expected_id=id_a) |
| 106 | |
| 107 | def test_cas_succeeds_on_first_write_when_expected_is_none(self, tmp_path: pathlib.Path) -> None: |
| 108 | repo = _make_bare_refs(tmp_path) |
| 109 | id_a = fake_id("a") |
| 110 | # expected_id=None means "no prior value" — valid for first commit on a branch |
| 111 | write_branch_ref(repo, "main", id_a, expected_id=None) |
| 112 | ref = (heads_dir(repo) / "main").read_text().strip() |
| 113 | assert ref == id_a |
| 114 | |
| 115 | def test_error_contains_branch_name_and_ids(self, tmp_path: pathlib.Path) -> None: |
| 116 | from muse.core.refs import RefConflictError |
| 117 | repo = _make_bare_refs(tmp_path) |
| 118 | id_a = fake_id("a") |
| 119 | id_b = fake_id("b") |
| 120 | id_c = fake_id("c") |
| 121 | write_branch_ref(repo, "dev", id_a) |
| 122 | with pytest.raises(RefConflictError, match="dev"): |
| 123 | write_branch_ref(repo, "dev", id_c, expected_id=id_b) |
| 124 | |
| 125 | |
| 126 | # --------------------------------------------------------------------------- |
| 127 | # Tier 2 — commit detects branch-moved condition |
| 128 | # |
| 129 | # The race window is between get_head_commit_id (parent read) and |
| 130 | # write_branch_ref (ref advance). We simulate it by patching |
| 131 | # get_head_commit_id to return a stale ID while the branch ref has already |
| 132 | # been advanced to a different commit by a "concurrent" agent. |
| 133 | # --------------------------------------------------------------------------- |
| 134 | |
| 135 | |
| 136 | class TestCommitDetectsBranchMoved: |
| 137 | def test_commit_fails_when_branch_advanced_concurrently( |
| 138 | self, muse_repo: pathlib.Path |
| 139 | ) -> None: |
| 140 | """If the branch ref advances between parent-read and ref-write, commit |
| 141 | must fail with a clear error rather than silently orphaning a commit.""" |
| 142 | from unittest.mock import patch |
| 143 | import json as _json |
| 144 | |
| 145 | f = muse_repo / "a.py" |
| 146 | f.write_text("v1\n") |
| 147 | _run(muse_repo, "code", "add", "a.py") |
| 148 | _run(muse_repo, "commit", "-m", "first") |
| 149 | |
| 150 | # Capture the real HEAD after the first commit |
| 151 | head_r = runner.invoke(None, ["rev-parse", "HEAD", "--json"], cwd=muse_repo) |
| 152 | real_parent = _json.loads(head_r.output)["commit_id"] |
| 153 | |
| 154 | branch_r = runner.invoke(None, ["rev-parse", "--abbrev-ref", "HEAD", "--json"], cwd=muse_repo) |
| 155 | branch = _json.loads(branch_r.output)["branch"] |
| 156 | |
| 157 | # Stage a change for the second commit |
| 158 | f.write_text("v2\n") |
| 159 | _run(muse_repo, "code", "add", "a.py") |
| 160 | |
| 161 | # Advance the branch ref to simulate another agent committing first |
| 162 | other_id = fake_id("other") |
| 163 | write_branch_ref(muse_repo, branch, other_id) |
| 164 | |
| 165 | # Patch get_head_commit_id so commit sees the STALE parent (real_parent), |
| 166 | # while the branch ref on disk is already at other_id. |
| 167 | # This exactly reproduces the race: parent_id read → branch advances → write fails. |
| 168 | with patch( |
| 169 | "muse.cli.commands.commit.get_head_commit_id", |
| 170 | return_value=real_parent, |
| 171 | ): |
| 172 | result = _try(muse_repo, "commit", "-m", "ours — should fail") |
| 173 | |
| 174 | assert result.exit_code != 0, ( |
| 175 | "commit succeeded despite branch moving concurrently — " |
| 176 | "this would have orphaned the concurrent commit" |
| 177 | ) |
| 178 | |
| 179 | def test_commit_succeeds_when_branch_has_not_moved( |
| 180 | self, muse_repo: pathlib.Path |
| 181 | ) -> None: |
| 182 | """Normal single-agent commit still works after the CAS fix.""" |
| 183 | f = muse_repo / "b.py" |
| 184 | f.write_text("hello\n") |
| 185 | _run(muse_repo, "code", "add", "b.py") |
| 186 | r = _try(muse_repo, "commit", "-m", "normal commit") |
| 187 | assert r.exit_code == 0, r.output |
| 188 | |
| 189 | def test_commit_error_message_is_actionable( |
| 190 | self, muse_repo: pathlib.Path |
| 191 | ) -> None: |
| 192 | """The error surfaced to the user must tell them to pull/retry.""" |
| 193 | from unittest.mock import patch |
| 194 | import json as _json |
| 195 | |
| 196 | f = muse_repo / "c.py" |
| 197 | f.write_text("v1\n") |
| 198 | _run(muse_repo, "code", "add", "c.py") |
| 199 | _run(muse_repo, "commit", "-m", "first") |
| 200 | |
| 201 | head_r = runner.invoke(None, ["rev-parse", "HEAD", "--json"], cwd=muse_repo) |
| 202 | real_parent = _json.loads(head_r.output)["commit_id"] |
| 203 | |
| 204 | branch_r = runner.invoke(None, ["rev-parse", "--abbrev-ref", "HEAD", "--json"], cwd=muse_repo) |
| 205 | branch = _json.loads(branch_r.output)["branch"] |
| 206 | |
| 207 | f.write_text("v2\n") |
| 208 | _run(muse_repo, "code", "add", "c.py") |
| 209 | |
| 210 | write_branch_ref(muse_repo, branch, fake_id("concurrent")) |
| 211 | |
| 212 | with patch( |
| 213 | "muse.cli.commands.commit.get_head_commit_id", |
| 214 | return_value=real_parent, |
| 215 | ): |
| 216 | result = _try(muse_repo, "commit", "-m", "should fail") |
| 217 | |
| 218 | combined = result.output + (result.stderr or "") |
| 219 | assert any( |
| 220 | kw in combined.lower() |
| 221 | for kw in ("conflict", "moved", "concurrent", "retry", "pull", "changed") |
| 222 | ), f"error output gave no actionable guidance:\n{combined}" |
| 223 | |
| 224 | |
| 225 | # --------------------------------------------------------------------------- |
| 226 | # Tier 3 — concurrent commit threads: only one succeeds per slot |
| 227 | # |
| 228 | # Two threads both read parent_id = A, both build a commit, both try to |
| 229 | # write the branch ref with expected_id=A. The first rename wins; the |
| 230 | # second finds current != A and raises RefConflictError. |
| 231 | # --------------------------------------------------------------------------- |
| 232 | |
| 233 | |
| 234 | class TestConcurrentCommitThreads: |
| 235 | def test_only_one_of_two_concurrent_commits_wins( |
| 236 | self, muse_repo: pathlib.Path |
| 237 | ) -> None: |
| 238 | """Two threads racing on write_branch_ref with the same expected_id: |
| 239 | exactly one must succeed and one must raise RefConflictError.""" |
| 240 | from muse.core.refs import RefConflictError |
| 241 | |
| 242 | (muse_repo / "base.py").write_text("base\n") |
| 243 | _run(muse_repo, "code", "add", "base.py") |
| 244 | _run(muse_repo, "commit", "-m", "base") |
| 245 | |
| 246 | import json as _json |
| 247 | head_r = runner.invoke(None, ["rev-parse", "HEAD", "--json"], cwd=muse_repo) |
| 248 | current = _json.loads(head_r.output)["commit_id"] |
| 249 | branch_r = runner.invoke(None, ["rev-parse", "--abbrev-ref", "HEAD", "--json"], cwd=muse_repo) |
| 250 | branch = _json.loads(branch_r.output)["branch"] |
| 251 | |
| 252 | id_a = fake_id("commit-a") |
| 253 | id_b = fake_id("commit-b") |
| 254 | |
| 255 | results: list[bool] = [] # True = success, False = RefConflictError |
| 256 | lock = threading.Lock() |
| 257 | barrier = threading.Barrier(2) |
| 258 | |
| 259 | def do_cas(new_id: str) -> None: |
| 260 | barrier.wait() # both threads start the CAS at the same moment |
| 261 | try: |
| 262 | write_branch_ref(muse_repo, branch, new_id, expected_id=current) |
| 263 | with lock: |
| 264 | results.append(True) |
| 265 | except RefConflictError: |
| 266 | with lock: |
| 267 | results.append(False) |
| 268 | |
| 269 | t1 = threading.Thread(target=do_cas, args=(id_a,)) |
| 270 | t2 = threading.Thread(target=do_cas, args=(id_b,)) |
| 271 | t1.start() |
| 272 | t2.start() |
| 273 | t1.join() |
| 274 | t2.join() |
| 275 | |
| 276 | successes = results.count(True) |
| 277 | assert successes == 1, ( |
| 278 | f"expected exactly 1 CAS success, got {successes}. results: {results}" |
| 279 | ) |
| 280 | assert results.count(False) == 1 |
File History
2 commits
sha256:43c82f6d4fa2e85dd9ed9dd1a31199ec6b481191517aba66dfa9da275dbfa1af
Merge branch 'dev' into main
Human
2 days ago
sha256:fb67fed5a4d3e40de84bdd163de94ef1386570bef1dd1a020a732c8a038962ce
Merge branch 'dev' into main
Human
21 days ago