ci: refresh PR mergeability before queue decisions

scripts/ci/pr_review_merge_scheduler.py

@@ -85,6 +85,17 @@
 OPEN_PRS_PAGE_SIZE = 25
 DEFAULT_STALE_OPENCODE_MINUTES = 45
 RUNNING_CHECK_STATES = {"PENDING", "EXPECTED", "QUEUED", "IN_PROGRESS", "WAITING", "REQUESTED"}
+REST_MERGEABLE_STATE_MAP = {
+    "behind": "BEHIND",
+    "blocked": "BLOCKED",
+    "clean": "CLEAN",
+    "dirty": "DIRTY",
+    "draft": "DRAFT",
+    "has_hooks": "HAS_HOOKS",
+    "unknown": "UNKNOWN",
+    "unstable": "UNSTABLE",
+}
+REST_MERGEABLE_STATES = set(REST_MERGEABLE_STATE_MAP.values())
 
 
 @dataclass
@@ -265,9 +276,44 @@ def fetch_open_prs(repo: str, max_prs: int) -> list[dict[str, Any]]:
             break
         cursor = pr_page["pageInfo"]["endCursor"]
 
+    enrich_rest_mergeable_states(repo, prs)
     return prs
 
 
+def fetch_rest_mergeable_state(repo: str, number: int) -> str:
+    """Fetch and normalize GitHub REST mergeable_state for one pull request."""
+    raw_state = run(
+        [
+            "gh",
+            "api",
+            f"repos/{repo}/pulls/{number}",
+            "--jq",
+            ".mergeable_state // \"\"",
+        ]
+    ).strip()
+    return REST_MERGEABLE_STATE_MAP.get(raw_state.lower(), raw_state.upper())
+
+
+def enrich_rest_mergeable_states(repo: str, prs: list[dict[str, Any]]) -> None:
+    """Attach REST mergeability evidence to GraphQL pull request payloads."""
+    for pr in prs:
+        try:
+            pr["restMergeableState"] = fetch_rest_mergeable_state(repo, int(pr["number"]))
+        except RuntimeError as exc:
+            pr["restMergeableStateError"] = bounded_error_summary(str(exc))
+
+
+def effective_merge_state(pr: dict[str, Any]) -> str:
+    """Return the safest merge state from GraphQL plus REST mergeability evidence."""
+    graph_state = (pr.get("mergeStateStatus") or "").upper()
+    rest_state = (pr.get("restMergeableState") or "").upper()
+    if rest_state in REST_MERGEABLE_STATES:
+        return rest_state
+    if graph_state in {"BEHIND", "DIRTY", "CONFLICTING", "UNKNOWN"}:
+        return graph_state
+    return rest_state or graph_state
+
+
 def context_nodes(pr: dict[str, Any]) -> list[dict[str, Any]]:
     """Return status rollup context nodes for a pull request payload."""
     rollup = pr.get("statusCheckRollup") or {}
@@ -576,7 +622,17 @@ def inspect_pr(
     if head_repo != repo:
         return Decision(number, "skip", f"fork or external head repo: {head_repo}")
 
-    merge_state = (pr.get("mergeStateStatus") or "").upper()
+    merge_state = effective_merge_state(pr)
+    if merge_state == "UNKNOWN":
+        if pr.get("autoMergeRequest"):
+            return disable_auto_merge_decision(
+                repo,
+                pr,
+                dry_run=dry_run,
+                reason="mergeability is still being calculated; wait for GitHub mergeability evidence before re-enabling auto-merge",
+            )
+        return Decision(number, "wait", "mergeability is still being calculated")
+
     if merge_state in {"DIRTY", "CONFLICTING"}:
         if pr.get("autoMergeRequest"):
             return disable_auto_merge_decision(
@@ -911,6 +967,7 @@ def self_test() -> None:
         "baseRefOid": "base",
         "headRefName": "feature",
         "mergeStateStatus": "CLEAN",
+        "restMergeableState": "CLEAN",
         "isDraft": False,
         "headRepository": {"nameWithOwner": "owner/repo"},
         "reviewDecision": "REVIEW_REQUIRED",
@@ -952,6 +1009,50 @@ def self_test() -> None:
         base_branch="main",
     )
     assert decision.action == "auto_merge"
+    sample["restMergeableState"] = "BEHIND"
+    decision = inspect_pr(
+        "owner/repo",
+        sample,
+        dry_run=True,
+        trigger_reviews=True,
+        enable_auto_merge_flag=True,
+        update_branches=True,
+        workflow="OpenCode Review",
+        security_workflow="Strix Security Scan",
+        base_branch="main",
+    )
+    assert decision.action == "update_branch"
+    sample["restMergeableState"] = "DIRTY"
+    sample["autoMergeRequest"] = {"enabledAt": "2026-01-01T00:02:00Z"}
+    decision = inspect_pr(
+        "owner/repo",
+        sample,
+        dry_run=True,
+        trigger_reviews=True,
+        enable_auto_merge_flag=True,
+        update_branches=True,
+        workflow="OpenCode Review",
+        security_workflow="Strix Security Scan",
+        base_branch="main",
+    )
+    assert decision.action == "disable_auto_merge"
+    assert "merge conflict: DIRTY" in decision.reason
+    sample["restMergeableState"] = "UNKNOWN"
+    sample["autoMergeRequest"] = None
+    decision = inspect_pr(
+        "owner/repo",
+        sample,
+        dry_run=True,
+        trigger_reviews=True,
+        enable_auto_merge_flag=True,
+        update_branches=True,
+        workflow="OpenCode Review",
+        security_workflow="Strix Security Scan",
+        base_branch="main",
+    )
+    assert decision.action == "wait"
+    assert "mergeability is still being calculated" in decision.reason
+    sample["restMergeableState"] = "CLEAN"
     sample["autoMergeRequest"] = {"enabledAt": "2026-01-01T00:02:00Z"}
     sample["statusCheckRollup"]["contexts"]["nodes"] = [
         {"__typename": "CheckRun", "name": "strix", "status": "COMPLETED", "conclusion": "FAILURE"}
@@ -1032,6 +1133,7 @@ def self_test() -> None:
     assert opencode_in_progress(sample)
     sample["statusCheckRollup"]["contexts"]["nodes"] = []
     sample["mergeStateStatus"] = "BEHIND"
+    sample["restMergeableState"] = ""
     sample["reviews"]["nodes"] = [
         {
             "state": "APPROVED",

tests/test_pr_review_merge_scheduler.py

@@ -14,6 +14,7 @@ def make_pr(**overrides):
         "isDraft": False,
         "mergeable": "MERGEABLE",
         "mergeStateStatus": "CLEAN",
+        "restMergeableState": "",
         "reviewDecision": "REVIEW_REQUIRED",
         "baseRefName": "main",
         "baseRefOid": "base",
@@ -163,6 +164,7 @@ def fake_graphql(query, **fields):
         return pages.pop(0)
 
     monkeypatch.setattr(sched, "gh_graphql", fake_graphql)
+    monkeypatch.setattr(sched, "enrich_rest_mergeable_states", lambda repo, prs: None)
     assert sched.fetch_open_prs("owner/repo", 3) == [{"number": 1}, {"number": 2}]
     assert seen[0]["pageSize"] == 3
     assert seen[1]["cursor"] == "cursor"
@@ -185,11 +187,38 @@ def fake_graphql(query, **fields):
         }
 
     monkeypatch.setattr(sched, "gh_graphql", fake_graphql)
+    monkeypatch.setattr(sched, "enrich_rest_mergeable_states", lambda repo, prs: None)
 
     assert sched.fetch_open_prs("owner/repo", 120) == [{"number": sched.OPEN_PRS_PAGE_SIZE}]
     assert seen[0]["pageSize"] == sched.OPEN_PRS_PAGE_SIZE
 
 
+def test_rest_mergeable_state_helpers(monkeypatch):
+    calls = []
+
+    def fake_run(args, stdin=None):
+        calls.append(args)
+        return "dirty\n"
+
+    monkeypatch.setattr(sched, "run", fake_run)
+
+    assert sched.fetch_rest_mergeable_state("owner/repo", 7) == "DIRTY"
+    assert calls == [["gh", "api", "repos/owner/repo/pulls/7", "--jq", ".mergeable_state // \"\""]]
+
+    prs = [{"number": 8}]
+    monkeypatch.setattr(sched, "fetch_rest_mergeable_state", lambda repo, number: f"{repo}:{number}")
+    sched.enrich_rest_mergeable_states("owner/repo", prs)
+    assert prs == [{"number": 8, "restMergeableState": "owner/repo:8"}]
+
+    def raise_lookup_error(repo, number):
+        raise RuntimeError("transient REST failure")
+
+    prs = [{"number": 9}]
+    monkeypatch.setattr(sched, "fetch_rest_mergeable_state", raise_lookup_error)
+    sched.enrich_rest_mergeable_states("owner/repo", prs)
+    assert prs == [{"number": 9, "restMergeableStateError": "transient REST failure"}]
+
+
 def test_context_review_and_check_helpers():
     assert sched.context_nodes({}) == []
     assert sched.context_nodes(make_pr()) == []
@@ -511,6 +540,35 @@ def test_inspect_pr_blocks_and_waits_for_policy_states(monkeypatch):
     conflicting = inspect(make_pr(mergeStateStatus="CONFLICTING"))
     assert conflicting.action == "block"
     assert "merge conflict: CONFLICTING" in conflicting.reason
+    rest_conflict = inspect(
+        make_pr(
+            mergeStateStatus="CLEAN",
+            restMergeableState="DIRTY",
+            autoMergeRequest={"enabledAt": "now"},
+        )
+    )
+    assert rest_conflict.action == "disable_auto_merge"
+    assert "merge conflict: DIRTY" in rest_conflict.reason
+    unknown_mergeability = inspect(make_pr(mergeStateStatus="CLEAN", restMergeableState="UNKNOWN"))
+    assert unknown_mergeability.action == "wait"
+    assert unknown_mergeability.reason == "mergeability is still being calculated"
+    unknown_auto_merge = inspect(
+        make_pr(
+            mergeStateStatus="CLEAN",
+            restMergeableState="UNKNOWN",
+            autoMergeRequest={"enabledAt": "now"},
+        )
+    )
+    assert unknown_auto_merge.action == "disable_auto_merge"
+    assert "mergeability is still being calculated" in unknown_auto_merge.reason
+    rest_clean = inspect(
+        make_pr(
+            mergeStateStatus="BEHIND",
+            restMergeableState="CLEAN",
+            reviews={"nodes": [opencode_review("APPROVED", "head")]},
+        )
+    )
+    assert rest_clean.action == "auto_merge"
     assert inspect(make_pr(reviewThreads={"nodes": [{"isResolved": False}]})).reason == "1 unresolved review thread(s)"
     unresolved_auto = inspect(
         make_pr(
@@ -567,6 +625,17 @@ def test_inspect_pr_blocks_and_waits_for_policy_states(monkeypatch):
     )
     assert inspect(behind_auto_merge_enabled).action == "update_branch"
     assert called == [("owner/repo", 1, True)]
+    called.clear()
+    rest_behind = make_pr(
+        mergeStateStatus="CLEAN",
+        restMergeableState="BEHIND",
+        reviews={"nodes": [opencode_review("APPROVED", "head")]},
+        autoMergeRequest={"enabledAt": "now"},
+    )
+    rest_behind_decision = inspect(rest_behind)
+    assert rest_behind_decision.action == "update_branch"
+    assert "github-actions[bot]" in rest_behind_decision.reason
+    assert called == [("owner/repo", 1, True)]
 
 
 def test_inspect_pr_handles_approved_reviews_and_dispatch(monkeypatch):