fix: return structured conflict-fix push assessment errors (Closes #519)

Resolve PR via pulls API before fetching lease comments so
gitea_assess_conflict_fix_push fails closed with actionable reasons
instead of surfacing HTTP 500 when Gitea returns not-found errors.

Add regression tests and document assessment-failure handoff in work-issue.

tests/test_assess_conflict_fix_push_tool.py

@@ -0,0 +1,139 @@
+"""Regression tests for gitea_assess_conflict_fix_push structured failures (#519)."""
+
+import os
+import sys
+import unittest
+from unittest.mock import patch
+
+sys.path.insert(0, str(__import__("pathlib").Path(__file__).resolve().parent.parent))
+
+from mcp_server import (  # noqa: E402
+    _fetch_pr_lease_comments_safe,
+    gitea_assess_conflict_fix_push,
+)
+
+FAKE_AUTH = "Basic dGVzdDp0ZXN0"
+AUTHOR_ENV = {
+    "GITEA_PROFILE_NAME": "prgs-author",
+    "GITEA_ALLOWED_OPERATIONS": "gitea.read,gitea.branch.push,gitea.pr.create",
+}
+
+HEAD_BEFORE = "dad1dc8d5108ab01ed83065334116d7425a4471c"
+HEAD_AFTER = "3f3d6cb35d0fe225dcb236247f2a2d0ec193fa35"
+OPEN_PR = {
+    "number": 508,
+    "state": "open",
+    "head": {"sha": HEAD_AFTER},
+}
+
+
+class TestFetchPrLeaseCommentsSafe(unittest.TestCase):
+    @patch("mcp_server.api_request")
+    @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
+    def test_pr_lookup_404_returns_structured_failure(self, _auth, mock_api):
+        mock_api.side_effect = RuntimeError(
+            'HTTP 404: {"message":"issue does not exist","index":508}'
+        )
+        result = _fetch_pr_lease_comments_safe(
+            508, remote="prgs", host=None, org=None, repo=None)
+        self.assertFalse(result["success"])
+        self.assertEqual(result["comments"], [])
+        self.assertTrue(result["reasons"])
+        self.assertIn("PR lookup failed", result["reasons"][0])
+        self.assertEqual(result["pr_lookup"], "failed")
+
+    @patch("mcp_server.api_request")
+    @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
+    def test_comment_fetch_404_after_pr_lookup(self, _auth, mock_api):
+        def _api(method, url, auth, *args, **kwargs):
+            if "/pulls/" in url:
+                return OPEN_PR
+            raise RuntimeError(
+                'HTTP 404: {"message":"issue does not exist","index":508}'
+            )
+
+        mock_api.side_effect = _api
+        result = _fetch_pr_lease_comments_safe(
+            508, remote="prgs", host=None, org=None, repo=None)
+        self.assertFalse(result["success"])
+        self.assertIn("comment fetch failed", result["reasons"][0].lower())
+        self.assertEqual(result["pr_lookup"], "ok")
+
+    @patch("mcp_server.api_request")
+    @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
+    def test_success_returns_comments_and_head_sha(self, _auth, mock_api):
+        comment = {"id": 1, "body": "<!-- mcp-conflict-fix-lease:v1 -->"}
+
+        def _api(method, url, auth, *args, **kwargs):
+            if "/pulls/" in url:
+                return OPEN_PR
+            return [comment]
+
+        mock_api.side_effect = _api
+        result = _fetch_pr_lease_comments_safe(
+            508, remote="prgs", host=None, org=None, repo=None)
+        self.assertTrue(result["success"])
+        self.assertEqual(result["comments"], [comment])
+        self.assertEqual(result["head_sha"], OPEN_PR["head"]["sha"])
+
+
+class TestAssessConflictFixPushTool(unittest.TestCase):
+    @patch("mcp_server._fetch_pr_lease_comments_safe")
+    @patch("mcp_server._profile_operation_gate", return_value=None)
+    def test_returns_structured_block_when_pr_lookup_fails(
+        self, _gate, mock_fetch,
+    ):
+        mock_fetch.return_value = {
+            "success": False,
+            "comments": [],
+            "reasons": ["PR lookup failed"],
+            "pr_lookup": "failed",
+            "resolved_repo": "Scaled-Tech-Consulting/Gitea-Tools",
+            "remote": "prgs",
+            "pr_number": 508,
+        }
+        with patch.dict(os.environ, AUTHOR_ENV, clear=True):
+            result = gitea_assess_conflict_fix_push(
+                pr_number=508,
+                branch_head_before=HEAD_BEFORE,
+                branch_head_after=HEAD_AFTER,
+                worktree_path="/proj/branches/fix-pr508",
+                push_cwd="/proj/branches/fix-pr508",
+                is_fast_forward=True,
+                remote="prgs",
+            )
+        self.assertFalse(result["push_allowed"])
+        self.assertTrue(result.get("assessment_failed"))
+        self.assertEqual(result["pr_lookup"], "failed")
+
+    @patch("mcp_server._fetch_pr_lease_comments_safe")
+    @patch("mcp_server._profile_operation_gate", return_value=None)
+    def test_valid_push_assessment_when_pr_and_comments_resolve(
+        self, _gate, mock_fetch,
+    ):
+        mock_fetch.return_value = {
+            "success": True,
+            "comments": [],
+            "reasons": [],
+            "pr_lookup": "ok",
+            "resolved_repo": "Scaled-Tech-Consulting/Gitea-Tools",
+            "remote": "prgs",
+            "pr_number": 508,
+            "head_sha": HEAD_AFTER,
+        }
+        with patch.dict(os.environ, AUTHOR_ENV, clear=True):
+            result = gitea_assess_conflict_fix_push(
+                pr_number=508,
+                branch_head_before=HEAD_BEFORE,
+                branch_head_after=HEAD_AFTER,
+                worktree_path="/proj/branches/fix-pr508",
+                push_cwd="/proj/branches/fix-pr508",
+                is_fast_forward=True,
+                remote="prgs",
+            )
+        self.assertTrue(result["push_allowed"])
+        self.assertEqual(result.get("live_pr_head_sha"), HEAD_AFTER)
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_pr_lease_comments_non_list_guard.py

@@ -16,13 +16,23 @@ AUTHOR_ENV = {
     "GITEA_PROFILE_NAME": "gitea-author",
     "GITEA_ALLOWED_OPERATIONS": "gitea.read,gitea.issue.comment",
 }
+OPEN_PR = {"number": 12, "state": "open", "head": {"sha": "abc123"}}
+
+
+def _pr_then_comments(mock_api, comments_payload):
+    def _api(method, url, auth, *args, **kwargs):
+        if "/pulls/" in url:
+            return OPEN_PR
+        return comments_payload
+
+    mock_api.side_effect = _api
 
 
 class TestPrLeaseCommentsNonListGuard(unittest.TestCase):
     @patch("mcp_server.api_request")
     @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
     def test_list_pr_lease_comments_non_list_payload_returns_empty(self, _auth, mock_api):
-        mock_api.return_value = {"message": "Unauthorized"}
+        _pr_then_comments(mock_api, {"message": "Unauthorized"})
         result = _list_pr_lease_comments(
             12, remote="prgs", host=None, org=None, repo=None)
         self.assertEqual(result, [])
@@ -30,7 +40,7 @@ class TestPrLeaseCommentsNonListGuard(unittest.TestCase):
     @patch("mcp_server.api_request")
     @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
     def test_list_pr_lease_comments_none_returns_empty(self, _auth, mock_api):
-        mock_api.return_value = None
+        _pr_then_comments(mock_api, None)
         result = _list_pr_lease_comments(
             12, remote="prgs", host=None, org=None, repo=None)
         self.assertEqual(result, [])
@@ -39,7 +49,7 @@ class TestPrLeaseCommentsNonListGuard(unittest.TestCase):
     @patch("mcp_server.get_auth_header", return_value=FAKE_AUTH)
     def test_list_pr_lease_comments_list_payload_unchanged(self, _auth, mock_api):
         comment = {"id": 7, "body": "<!-- mcp-review-lease:v1 -->"}
-        mock_api.return_value = [comment]
+        _pr_then_comments(mock_api, [comment])
         result = _list_pr_lease_comments(
             12, remote="prgs", host=None, org=None, repo=None, limit=5)
         self.assertEqual(result, [comment])