Fix : Search for previous tag by Git tag, not by GitHub release

DEVGUIDE.md

@@ -1023,6 +1023,20 @@ for commit in repo.get_commits():  # Paginated API calls!
 
 ### Testing Requirements
 
+**Local development setup**:
+
+```bash
+# Create and activate a virtual environment
+python3 -m venv .venv
+source .venv/bin/activate
+
+# Install package with dependencies
+pip install .
+
+# Install dev tools
+pip install pytest pytest-cov black flake8 mypy boto3
+```
+
 **Before submitting changes**:
 
 ```bash

tagbot/action/changelog.py

@@ -4,6 +4,7 @@
 from datetime import datetime, timedelta, timezone
 from typing import TYPE_CHECKING, Dict, List, Optional, Tuple, Union
 
+from github import UnknownObjectException
 from github.GitRelease import GitRelease
 from github.Issue import Issue
 from github.NamedUser import NamedUser
@@ -49,12 +50,13 @@ def _previous_release(self, version_tag: str) -> Optional[GitRelease]:
         cur_ver = VersionInfo.parse(version_tag[i_start:])
         prev_ver = VersionInfo(0)
         prev_rel = None
-        tag_prefix = self._repo._tag_prefix()
-        for r in self._repo._repo.get_releases():
-            if not r.tag_name.startswith(tag_prefix):
+        tags = self._repo.get_all_tags()
+
+        for tag_name in tags:
+            if not tag_name.startswith(tag_prefix):
                 continue
             try:
-                ver = VersionInfo.parse(r.tag_name[i_start:])
+                ver = VersionInfo.parse(tag_name[i_start:])
             except ValueError:
                 continue
             if ver.prerelease or ver.build:
@@ -63,7 +65,17 @@ def _previous_release(self, version_tag: str) -> Optional[GitRelease]:
             # That means if we're creating a backport v1.1, an already existing v2.0,
             # despite being newer than v1.0, will not be selected.
             if ver < cur_ver and ver > prev_ver:
-                prev_rel = r
+                # Get the GitHub release for this tag if it exists
+                try:
+                    prev_rel = self._repo._repo.get_release(tag_name)
+                except UnknownObjectException:
+                    # Release doesn't exist - get commit datetime from the tag
+                    commit_time = self._repo._git.time_of_commit(tag_name)
+                    prev_rel = type(
+                        "obj",
+                        (object,),
+                        {"tag_name": tag_name, "created_at": commit_time},
+                    )()
                 prev_ver = ver
         return prev_rel
 
@@ -75,8 +87,8 @@ def _is_backport(self, version: str, tags: Optional[List[str]] = None) -> bool:
             )
 
             if tags is None:
-                # Populate the tags list with tag names from the releases
-                tags = [r.tag_name for r in self._repo._repo.get_releases()]
+                # Use Git tags instead of GitHub releases
+                tags = self._repo.get_all_tags()
 
             # Extract any package name prefix and version number from the input
             match = version_pattern.match(version)
@@ -266,7 +278,8 @@ def _collect_data(self, version_tag: str, sha: str) -> Dict[str, object]:
         prev_tag = None
         compare = None
         if previous:
-            start = previous.created_at
+            if previous.created_at:
+                start = previous.created_at
             prev_tag = previous.tag_name
             compare = f"{self._repo._repo.html_url}/compare/{prev_tag}...{version_tag}"
         # When the last commit is a PR merge, the commit happens a second or two before

tagbot/action/repo.py

@@ -700,6 +700,15 @@ def _highest_existing_version(self) -> Optional[VersionInfo]:
 
         return highest
 
+    def get_all_tags(self) -> List[str]:
+        """Get all Git tag names in the repository.
+
+        Returns a list of tag names (without 'refs/tags/' prefix).
+        Uses the tags cache to avoid repeated API calls.
+        """
+        tags_cache = self._build_tags_cache()
+        return list(tags_cache.keys())
+
     def version_with_latest_commit(self, versions: Dict[str, str]) -> Optional[str]:
         """Find the version with the most recent commit datetime.
 

test/action/test_changelog.py

@@ -42,7 +42,11 @@ def test_slug():
 def test_previous_release():
     c = _changelog()
     tags = ["ignore", "v1.2.4-ignore", "v1.2.3", "v1.2.2", "v1.0.2", "v1.0.10"]
-    c._repo._repo.get_releases = Mock(return_value=[Mock(tag_name=t) for t in tags])
+    c._repo.get_all_tags = Mock(return_value=tags)
+    # Mock get_release to return a minimal release-like object
+    c._repo._repo.get_release = Mock(
+        side_effect=lambda tag: type("obj", (object,), {"tag_name": tag})()
+    )
     assert c._previous_release("v1.0.0") is None
     assert c._previous_release("v1.0.2") is None
     rel = c._previous_release("v1.2.5")
@@ -51,6 +55,29 @@ def test_previous_release():
     assert rel and rel.tag_name == "v1.0.2"
 
 
+def test_previous_release_no_github_release():
+    """Test that _previous_release falls back to commit time when no GitHub release."""
+    from datetime import datetime
+    from github import UnknownObjectException
+
+    c = _changelog()
+    tags = ["v1.0.0", "v1.1.0"]
+    c._repo.get_all_tags = Mock(return_value=tags)
+    # Simulate no GitHub release existing for the tag
+    c._repo._repo.get_release = Mock(
+        side_effect=UnknownObjectException(404, "Not Found", {})
+    )
+    # Mock time_of_commit to return a datetime
+    mock_time = datetime(2025, 1, 1, 12, 0, 0)
+    c._repo._git.time_of_commit = Mock(return_value=mock_time)
+
+    rel = c._previous_release("v1.1.1")
+    assert rel is not None
+    assert rel.tag_name == "v1.1.0"
+    assert rel.created_at == mock_time
+    c._repo._git.time_of_commit.assert_called_with("v1.1.0")
+
+
 def test_previous_release_subdir():
     True
     c = _changelog(subdir="Foo")
@@ -67,7 +94,11 @@ def test_previous_release_subdir():
         "v2.0.1",
         "Foo-v2.0.0",
     ]
-    c._repo._repo.get_releases = Mock(return_value=[Mock(tag_name=t) for t in tags])
+    c._repo.get_all_tags = Mock(return_value=tags)
+    # Mock get_release to return a minimal release-like object
+    c._repo._repo.get_release = Mock(
+        side_effect=lambda tag: type("obj", (object,), {"tag_name": tag})()
+    )
     assert c._previous_release("Foo-v1.0.0") is None
     assert c._previous_release("Foo-v1.0.2") is None
     rel = c._previous_release("Foo-v1.2.5")