fix(source-control): page the merge gate's force-push read

.changes/source-control/fix-force-push-read-pages-1473d48c.md

@@ -0,0 +1,7 @@
+---
+bump: patch
+---
+
+### Fixed
+
+- The babysit merge gate reads a pull request's force pushes 100 at a time up to 1,000, so a pull request rebased more than 100 times no longer fails its risk gate with `force pushes: unread or past one page` on every run and never arms. A listing past 1,000, a missing cursor or a count the pages do not reach still raises.

plugins/source-control/skills/babysit-prs/scripts/babysit_merge.py

@@ -3337,19 +3337,26 @@ def _main_reviews(
 
 
 _FORCE_PUSHES_QUERY = (
-    "query($o:String!,$r:String!,$n:Int!){repository(owner:$o,name:$r){"
-    "pullRequest(number:$n){timelineItems(first:100,itemTypes:[HEAD_REF_FORCE_PUSHED_EVENT])"
-    "{totalCount nodes{... on HeadRefForcePushedEvent{beforeCommit{oid}}}}}}}"
+    "query($o:String!,$r:String!,$n:Int!,$c:String){repository(owner:$o,name:$r){"
+    "pullRequest(number:$n){timelineItems(first:100,after:$c,itemTypes:[HEAD_REF_FORCE_PUSHED_EVENT])"
+    "{totalCount pageInfo{hasNextPage endCursor}"
+    "nodes{... on HeadRefForcePushedEvent{beforeCommit{oid}}}}}}}"
 )
+# A pull request rebased more often than this is past what the gate reads.
+_FORCE_PUSH_PAGES = 10
 
 
 def _force_pushed_heads(repo: str, number: int) -> list[str]:
     """The heads force pushes replaced, which the commits list no longer
-    names but whose recorded counts still hold. Any doubt raises, so the
-    evidence is unbound rather than missing a count."""
+    names but whose recorded counts still hold, read a page of 100 at a time
+    up to _FORCE_PUSH_PAGES. Any doubt raises, so the evidence is unbound
+    rather than missing a count."""
     owner, name = repo.split("/", 1)
-    data = gh_json_graphql(
-        [
+    nodes: list[Any] = []
+    cursor = None
+    total = None
+    for _ in range(_FORCE_PUSH_PAGES):
+        args = [
             "api",
             "graphql",
             "-f",
@@ -3360,19 +3367,32 @@ def _force_pushed_heads(repo: str, number: int) -> list[str]:
             f"r={name}",
             "-F",
             f"n={number}",
-        ],
-        label=f"#{number} force pushes",
-    )
-    items = json_object(
-        json_object(
+        ]
+        if cursor is not None:
+            args += ["-f", f"c={cursor}"]
+        data = gh_json_graphql(args, label=f"#{number} force pushes")
+        items = json_object(
             json_object(
-                json_object(json_object(data).get("data")).get("repository")
-            ).get("pullRequest")
-        ).get("timelineItems")
-    )
-    nodes = items.get("nodes")
-    if not is_json_array(nodes) or items.get("totalCount") != len(nodes):
-        raise RuntimeError(f"#{number} force pushes: unread or past one page")
+                json_object(
+                    json_object(json_object(data).get("data")).get("repository")
+                ).get("pullRequest")
+            ).get("timelineItems")
+        )
+        page = items.get("nodes")
+        info = json_object(items.get("pageInfo"))
+        if not is_json_array(page):
+            raise RuntimeError(f"#{number} force pushes: unread")
+        total = items.get("totalCount")
+        nodes.extend(page)
+        if info.get("hasNextPage") is not True:
+            break
+        cursor = info.get("endCursor")
+        if not isinstance(cursor, str) or not cursor:
+            raise RuntimeError(f"#{number} force pushes: unread")
+    else:
+        raise RuntimeError(f"#{number} force pushes: past {_FORCE_PUSH_PAGES} pages")
+    if total != len(nodes):
+        raise RuntimeError(f"#{number} force pushes: unread or incomplete")
     heads = []
     for node in nodes:
         oid = json_object(json_object(node).get("beforeCommit")).get("oid")

plugins/source-control/skills/babysit-prs/scripts/tests/test_babysit_merge.py

@@ -2502,7 +2502,14 @@ def collect(repo, names, workflow, branch, env):
             ),
         ):
             reviews, context = merge._main_reviews(
-                "owner/repo", 5, HEAD, changed, None, None, None, [HEAD],
+                "owner/repo",
+                5,
+                HEAD,
+                changed,
+                None,
+                None,
+                None,
+                [HEAD],
                 floor=merge.babysit_risk.floor_for(),
             )
         calls.extend(read.call_args_list)
@@ -2620,32 +2627,62 @@ def test_any_other_pull_request_lists_every_lane(self) -> None:
 
 class ForcePushedHeadsTests(unittest.TestCase):
     """The heads force pushes replaced, whose recorded review counts still
-    hold; a listing that is not whole raises."""
+    hold, read across pages; a listing that is not whole raises."""
 
-    def heads(self, total: int, oids: list[Any]) -> list[str]:
+    @staticmethod
+    def page(total: int, oids: list[Any], cursor: str | None = None) -> dict:
         nodes = [
             {"beforeCommit": None if oid is None else {"oid": oid}} for oid in oids
         ]
-        data = {
+        info = {"hasNextPage": cursor is not None, "endCursor": cursor}
+        return {
             "data": {
                 "repository": {
                     "pullRequest": {
-                        "timelineItems": {"totalCount": total, "nodes": nodes}
+                        "timelineItems": {
+                            "totalCount": total,
+                            "pageInfo": info,
+                            "nodes": nodes,
+                        }
                     }
                 }
             }
         }
-        with mock.patch.object(merge, "gh_json_graphql", return_value=data):
-            return merge._force_pushed_heads("owner/repo", 5)
+
+    def heads(self, *pages: dict) -> tuple[list[str], mock.MagicMock]:
+        with mock.patch.object(
+            merge, "gh_json_graphql", side_effect=list(pages)
+        ) as read:
+            return merge._force_pushed_heads("owner/repo", 5), read
 
     def test_names_each_replaced_head(self) -> None:
-        self.assertEqual(
-            self.heads(3, ["a" * 40, None, "b" * 40]), ["a" * 40, "b" * 40]
+        heads, _ = self.heads(self.page(3, ["a" * 40, None, "b" * 40]))
+        self.assertEqual(heads, ["a" * 40, "b" * 40])
+
+    def test_reads_every_page_by_its_cursor(self) -> None:
+        heads, read = self.heads(
+            self.page(101, ["a" * 40] * 100, cursor="next"),
+            self.page(101, ["b" * 40]),
         )
+        self.assertEqual(heads, ["a" * 40] * 100 + ["b" * 40])
+        self.assertNotIn("c=next", read.call_args_list[0].args[0])
+        self.assertIn("c=next", read.call_args_list[1].args[0])
+
+    def test_a_count_the_pages_do_not_reach_raises(self) -> None:
+        with self.assertRaises(RuntimeError):
+            self.heads(self.page(101, ["a" * 40]))
+
+    def test_a_next_page_with_no_cursor_raises(self) -> None:
+        with self.assertRaises(RuntimeError):
+            self.heads(self.page(200, ["a" * 40], cursor=""))
 
-    def test_a_listing_past_one_page_raises(self) -> None:
+    def test_a_listing_past_the_page_cap_raises(self) -> None:
+        pages = [
+            self.page(9999, ["a" * 40], cursor=f"c{i}")
+            for i in range(merge._FORCE_PUSH_PAGES)
+        ]
         with self.assertRaises(RuntimeError):
-            self.heads(101, ["a" * 40])
+            self.heads(*pages)
 
 
 if __name__ == "__main__":