Project: build both default and latest version when saving the project form (#11177)

* Project: build both default and latest version when saving the project form

Closes #9685

* Lint

* Fix call to reverse

* Fix mock patch

Author: stsewd

readthedocs/projects/forms.py

@@ -63,6 +63,9 @@ class ProjectTriggerBuildMixin:
     """
     Mixin to trigger build on form save.
 
+    We trigger a build to the default branch and the LATEST version of the project,
+    since both are related, latest is an alias of the default version.
+
     This should be replaced with signals instead of calling trigger_build
     explicitly.
     """
@@ -71,7 +74,18 @@ def save(self, commit=True):
         """Trigger build on commit save."""
         project = super().save(commit)
         if commit:
-            trigger_build(project=project)
+            default_branch = project.versions.filter(
+                slug=project.get_default_branch()
+            ).first()
+            if default_branch and default_branch.active:
+                trigger_build(project=project, version=default_branch)
+            latest_version = project.get_latest_version()
+            if (
+                latest_version
+                and latest_version != default_branch
+                and latest_version.active
+            ):
+                trigger_build(project=project, version=latest_version)
         return project