Versions: always keep latest in sync with default branch/tag (#12121)

We had two ways of keeping latest in sync with the default branch chosen
by the user, one on project save and another one when syncing versions,
they are slightly different leading to some inconsistencies. We now
always use update_latest_version.

Closes #12029

Author: stsewd

readthedocs/projects/models.py

@@ -643,19 +643,7 @@ def save(self, *args, **kwargs):
             self.repo = self.remote_repository.clone_url
 
         super().save(*args, **kwargs)
-
-        try:
-            if not self.versions.filter(slug=LATEST).exists():
-                self.versions.create_latest()
-        except Exception:
-            log.exception("Error creating default branches")
-
-        # Update `Version.identifier` for `latest` with the default branch the user has selected,
-        # even if it's `None` (meaning to match the `default_branch` of the repository)
-        # NOTE: this code is required to be *after* ``create_latest()``.
-        # It has to be updated after creating LATEST originally.
-        log.debug("Updating default branch.", slug=LATEST, identifier=self.default_branch)
-        self.versions.filter(slug=LATEST, machine=True).update(identifier=self.default_branch)
+        self.update_latest_version()
 
     def delete(self, *args, **kwargs):
         from readthedocs.projects.tasks.utils import clean_project_resources

readthedocs/projects/tests/test_build_tasks.py

@@ -840,6 +840,7 @@ def test_build_commands_executed(
                     "--prune-tags",
                     "--depth",
                     "50",
+                    "refs/heads/master:refs/remotes/origin/master",
                 ),
                 mock.call(
                     "git",

readthedocs/rtd_tests/tests/test_project_forms.py

@@ -8,7 +8,7 @@
 from django.test.utils import override_settings
 from django_dynamic_fixture import get
 
-from readthedocs.builds.constants import EXTERNAL, LATEST, STABLE
+from readthedocs.builds.constants import EXTERNAL, LATEST, LATEST_VERBOSE_NAME, STABLE, TAG, BRANCH
 from readthedocs.builds.models import Version
 from readthedocs.core.forms import RichValidationError
 from readthedocs.oauth.models import RemoteRepository, RemoteRepositoryRelation
@@ -419,7 +419,10 @@ def test_set_remote_repository(self):
 
 class TestProjectAdvancedFormDefaultBranch(TestCase):
     def setUp(self):
-        self.project = get(Project)
+        self.project = get(
+            Project,
+            repo="https://github.com/readthedocs/readthedocs.org/",
+        )
         user_created_stable_version = get(
             Version,
             project=self.project,
@@ -530,6 +533,57 @@ def test_external_version_not_in_default_branch_choices(self):
             ],
         )
 
+    @mock.patch("readthedocs.projects.forms.trigger_build")
+    def test_change_default_branch_from_tag_to_branch_and_vice_versa(self, trigger_build):
+        branch = get(
+            Version,
+            project=self.project,
+            slug="branch",
+            type=BRANCH,
+            verbose_name="branch",
+            identifier="branch",
+        )
+        tag = get(
+            Version,
+            project=self.project,
+            slug="tag",
+            type=TAG,
+            verbose_name="tag",
+            identifier="1234abcd",
+        )
+
+        data = {
+            "name": self.project.name,
+            "repo": self.project.repo,
+            "repo_type": self.project.repo_type,
+            "default_version": LATEST,
+            "versioning_scheme": self.project.versioning_scheme,
+            "language": self.project.language,
+            "default_branch": branch.verbose_name,
+        }
+        form = UpdateProjectForm(data, instance=self.project)
+        assert form.is_valid()
+        form.save()
+
+        self.project.refresh_from_db()
+        latest = self.project.get_latest_version()
+        assert latest.slug == LATEST
+        assert latest.verbose_name == LATEST_VERBOSE_NAME
+        assert latest.identifier == branch.verbose_name
+        assert latest.type == BRANCH
+
+        data["default_branch"] = tag.verbose_name
+        form = UpdateProjectForm(data, instance=self.project)
+        assert form.is_valid()
+        form.save()
+
+        self.project.refresh_from_db()
+        latest = self.project.get_latest_version()
+        assert latest.slug == LATEST
+        assert latest.verbose_name == LATEST_VERBOSE_NAME
+        assert latest.identifier == tag.verbose_name
+        assert latest.type == TAG
+
 
 @override_settings(RTD_ALLOW_ORGANIZATIONS=False)
 class TestProjectPrevalidationForms(TestCase):