Add utility method for explicitly setting cache tags to cache tag class

readthedocs/api/mixins.py

@@ -17,11 +17,8 @@ class CDNCacheTagsMixin:
     """
     Add cache tags for project and version to the response of this view.
 
-    The view inheriting this mixin should implement the
-    `self._get_project` and `self._get_version` methods.
-
-    If `self._get_version` returns `None`,
-    only the project level tags are added.
+    The view inheriting this mixin can either call :py:method:`set_cache_tags` or
+    implement the ``self._get_project`` and ``self._get_version`` methods.
 
     You can add an extra per-project tag by overriding the `project_cache_tag` attribute.
     """
@@ -30,29 +27,40 @@ class CDNCacheTagsMixin:
 
     def dispatch(self, request, *args, **kwargs):
         response = super().dispatch(request, *args, **kwargs)
-        cache_tags = self._get_cache_tags()
+        cache_tags = getattr(self, "_cache_tags", self._get_cache_tags())
         if cache_tags:
             add_cache_tags(response, cache_tags)
         return response
 
-    def _get_cache_tags(self):
+    def _get_cache_tags(self, project=None, version=None):
         """
         Get cache tags for this view.
 
+        This returns an array of tag identifiers used to tag the response at CDN.
+
+        If project and version are not passed in, these values will come from the
+        methods ``_get_project()`` and ``_get_version()``.
+        If ``_get_version()`` returns ``None``, only the project level tags are added.
+
+        It's easier to use :py:method:`set_cache_tags` if project/version aren't
+        set at the instance level, or if they are passed in through a method
+        like ``get()``.
+
         .. warning::
 
            This method is run at the end of the request,
            so any exceptions like 404 should be caught.
         """
-        try:
-            project = self._get_project()
-            version = self._get_version()
-        except Exception:
-            log.warning(
-                "Error while retrieving project or version for this view.",
-                exc_info=True,
-            )
-            return []
+        if project is None and version is None:
+            try:
+                project = self._get_project()
+                version = self._get_version()
+            except Exception:
+                log.warning(
+                    "Error while retrieving project or version for this view.",
+                    exc_info=True,
+                )
+                return []
 
         tags = []
         if project:
@@ -63,6 +71,19 @@ def _get_cache_tags(self):
             tags.append(get_cache_tag(project.slug, self.project_cache_tag))
         return tags
 
+    def set_cache_tags(self, project=None, version=None):
+        """
+        Store cache tags to be added to response.
+
+        This method can be used if project/version do not exist on the view
+        instance or if they are passed into the view through a method like
+        ``get()``.
+
+        The attribute methods ``_get_project()``/``_get_version()`` aren`t used
+        in this pattern.
+        """
+        self._cache_tags = self._get_cache_tags(project, version)
+
 
 class EmbedAPIMixin:
     """

readthedocs/projects/views/public.py

@@ -23,6 +23,7 @@
 from django.views.generic import ListView
 from taggit.models import Tag
 
+from readthedocs.api.mixins import CDNCacheTagsMixin
 from readthedocs.builds.constants import BUILD_STATE_FINISHED
 from readthedocs.builds.constants import EXTERNAL
 from readthedocs.builds.constants import INTERNAL
@@ -299,7 +300,7 @@ def verify_project_token(cls, token, project_slug):
 project_badge = never_cache(ProjectBadgeView.as_view())
 
 
-class ProjectDownloadMediaBase(CDNCacheControlMixin, ServeDocsMixin, View):
+class ProjectDownloadMediaBase(CDNCacheControlMixin, CDNCacheTagsMixin, ServeDocsMixin, View):
     # Use new-style URLs (same domain as docs) or old-style URLs (dashboard URL)
     same_domain_url = False
 
@@ -382,6 +383,8 @@ def get(
                 slug=version_slug,
             )
 
+        self.set_cache_tags(project=version.project, version=version)
+
         return self._serve_dowload(
             request=request,
             project=version.project,

readthedocs/proxito/tests/test_full.py

@@ -547,6 +547,7 @@ def test_download_files_public_version(self):
                 headers={"host": "project.dev.readthedocs.io"},
             )
             self.assertEqual(resp.status_code, 200)
+            self.assertEqual(resp["Cache-Tag"], "project,project:latest")
             extension = "zip" if type_ == MEDIA_TYPE_HTMLZIP else type_
             self.assertEqual(
                 resp["X-Accel-Redirect"],
@@ -560,6 +561,7 @@ def test_download_files_public_version(self):
                 headers={"host": "project.dev.readthedocs.io"},
             )
             self.assertEqual(resp.status_code, 200)
+            self.assertEqual(resp["Cache-Tag"], "translation,translation:latest")
             extension = "zip" if type_ == MEDIA_TYPE_HTMLZIP else type_
             self.assertEqual(
                 resp["X-Accel-Redirect"],
@@ -604,6 +606,7 @@ def test_download_files_private_version(self):
                 headers={"host": "project.dev.readthedocs.io"},
             )
             self.assertEqual(resp.status_code, 200)
+            self.assertEqual(resp["Cache-Tag"], "project,project:latest")
             extension = "zip" if type_ == MEDIA_TYPE_HTMLZIP else type_
             self.assertEqual(
                 resp["X-Accel-Redirect"],