Proxito: redirect to default version from root language (#10313)

Closes #2968

---------

Co-authored-by: Benjamin Balder Bach <[email protected]>

Author: stsewd

docs/user/user-defined-redirects.rst

@@ -84,6 +84,22 @@ For example::
 You can choose which is the :term:`default version` for Read the Docs to display.
 This usually corresponds to the most recent official release from your project.
 
+Root language redirect at ``/<lang>/``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+A link to the root language of your documentation (``<slug>.readthedocs.io/en/``)
+will redirect to the  :term:`default version` of that language.
+
+.. TODO: Remove this once the feature is default on .com
+
+This redirect is currently only active on |org_brand| (``<slug>.readthedocs.io`` and :doc:`custom domains </custom-domains>`).
+
+Root language redirects on |com_brand| can be enabled by contacting :doc:`support </support>`.
+
+For example, accessing the English language of the project will redirect you to the its version (``stable``)::
+
+   https://docs.readthedocs.io/en/ -> https://docs.readthedocs.io/en/stable/
+
 Shortlink with ``https://<slug>.rtfd.io``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

readthedocs/core/unresolver.py

@@ -60,6 +60,12 @@ def __init__(self, project, language, version_slug, filename):
         self.version_slug = version_slug
 
 
+class TranslationWithoutVersionError(UnresolverError):
+    def __init__(self, project, language):
+        self.project = project
+        self.language = language
+
+
 class InvalidPathForVersionedProjectError(UnresolverError):
     def __init__(self, project, path):
         self.project = project
@@ -272,6 +278,14 @@ def _match_multiversion_project(
                     filename=file,
                 )
 
+        # If only the language part was given,
+        # we can't resolve the version.
+        if version_slug is None:
+            raise TranslationWithoutVersionError(
+                project=project,
+                language=language,
+            )
+
         if external_version_slug and external_version_slug != version_slug:
             raise InvalidExternalVersionError(
                 project=project,

readthedocs/proxito/tests/test_redirects.py

@@ -2,6 +2,8 @@
 from django.test import override_settings
 from django_dynamic_fixture import get
 
+from readthedocs.builds.models import Version
+from readthedocs.projects.constants import PUBLIC
 from readthedocs.projects.models import Feature
 from readthedocs.proxito.constants import RedirectType
 from readthedocs.subscriptions.constants import TYPE_CNAME
@@ -11,6 +13,7 @@
 
 @override_settings(
     PUBLIC_DOMAIN='dev.readthedocs.io',
+    RTD_EXTERNAL_VERSION_DOMAIN="dev.readthedocs.build",
     PUBLIC_DOMAIN_USES_HTTPS=True,
     RTD_DEFAULT_FEATURES={
         TYPE_CNAME: 1,
@@ -412,3 +415,49 @@ def setUp(self):
             default_true=True,
             future_default_true=True,
         )
+
+    def test_redirect_from_root_language_to_default_version(self):
+        paths = [
+            "/en",
+            "/en/",
+        ]
+        for path in paths:
+            r = self.client.get(
+                path,
+                secure=True,
+                HTTP_HOST="project.dev.readthedocs.io",
+            )
+            self.assertEqual(r.status_code, 302)
+            self.assertEqual(
+                r["Location"],
+                "https://project.dev.readthedocs.io/en/latest/",
+            )
+            self.assertEqual(r.headers["CDN-Cache-Control"], "public")
+            self.assertEqual(r.headers["Cache-Tag"], "project")
+            self.assertEqual(r.headers["X-RTD-Redirect"], RedirectType.system.name)
+
+    def test_redirect_from_root_language_to_default_external_version(self):
+        get(
+            Version,
+            slug="10",
+            project=self.project,
+            privacy_level=PUBLIC,
+        )
+        paths = [
+            "/en",
+            "/en/",
+        ]
+        for path in paths:
+            r = self.client.get(
+                path,
+                secure=True,
+                HTTP_HOST="project--10.dev.readthedocs.build",
+            )
+            self.assertEqual(r.status_code, 302)
+            self.assertEqual(
+                r["Location"],
+                "https://project--10.dev.readthedocs.build/en/10/",
+            )
+            self.assertEqual(r.headers["CDN-Cache-Control"], "public")
+            self.assertEqual(r.headers["Cache-Tag"], "project")
+            self.assertEqual(r.headers["X-RTD-Redirect"], RedirectType.system.name)

readthedocs/proxito/views/serve.py

@@ -19,6 +19,7 @@
     InvalidExternalVersionError,
     InvalidPathForVersionedProjectError,
     TranslationNotFoundError,
+    TranslationWithoutVersionError,
     VersionNotFoundError,
     unresolver,
 )
@@ -357,6 +358,25 @@ def get_using_unresolver(self, request):
             # TODO: find a better way to pass this to the middleware.
             request.path_project_slug = exc.project.slug
             raise Http404
+        except TranslationWithoutVersionError as exc:
+            project = exc.project
+            # TODO: find a better way to pass this to the middleware.
+            request.path_project_slug = project.slug
+
+            if unresolved_domain.is_from_external_domain:
+                version_slug = unresolved_domain.external_version_slug
+            else:
+                version_slug = None
+            # Redirect to the default version of the current translation.
+            # This is `/en -> /en/latest/` or
+            # `/projects/subproject/en/ -> /projects/subproject/en/latest/`.
+            return self.system_redirect(
+                request=request,
+                final_project=project,
+                version_slug=version_slug,
+                filename="",
+                is_external_version=unresolved_domain.is_from_external_domain,
+            )
         except InvalidPathForVersionedProjectError as exc:
             project = exc.project
             if unresolved_domain.is_from_external_domain:
@@ -745,7 +765,9 @@ def get_using_unresolver(self, request, path):
 
         project = None
         version = None
-        filename = None
+        # If we weren't able to resolve a filename,
+        # then the path is the filename.
+        filename = path
         lang_slug = None
         version_slug = None
         # Try to map the current path to a project/version/filename.
@@ -778,6 +800,10 @@ def get_using_unresolver(self, request, path):
             version_slug = exc.version_slug
             filename = exc.filename
             contextualized_404_class = ProjectTranslationHttp404
+        except TranslationWithoutVersionError as exc:
+            project = exc.project
+            lang_slug = exc.language
+            # TODO: Use a contextualized 404
         except InvalidExternalVersionError as exc:
             project = exc.project
             # TODO: Use a contextualized 404

readthedocs/rtd_tests/tests/test_unresolver.py

@@ -12,6 +12,7 @@
     InvalidPathForVersionedProjectError,
     SuspiciousHostnameError,
     TranslationNotFoundError,
+    TranslationWithoutVersionError,
     VersionNotFoundError,
     unresolve,
 )
@@ -99,10 +100,34 @@ def test_path_no_version(self):
             "https://pip.readthedocs.io/en/",
         ]
         for url in urls:
-            with pytest.raises(VersionNotFoundError) as excinfo:
+            with pytest.raises(TranslationWithoutVersionError) as excinfo:
                 unresolve(url)
             exc = excinfo.value
             self.assertEqual(exc.project, self.pip)
+            self.assertEqual(exc.language, "en")
+
+        urls = [
+            "https://pip.readthedocs.io/ja",
+            "https://pip.readthedocs.io/ja/",
+        ]
+        for url in urls:
+            with pytest.raises(TranslationWithoutVersionError) as excinfo:
+                unresolve(url)
+            exc = excinfo.value
+            self.assertEqual(exc.project, self.translation)
+            self.assertEqual(exc.language, "ja")
+
+    def test_invalid_language_no_version(self):
+        urls = [
+            "https://pip.readthedocs.io/es",
+            "https://pip.readthedocs.io/es/",
+        ]
+        for url in urls:
+            with pytest.raises(TranslationNotFoundError) as excinfo:
+                unresolve(url)
+            exc = excinfo.value
+            self.assertEqual(exc.project, self.pip)
+            self.assertEqual(exc.language, "es")
             self.assertEqual(exc.version_slug, None)
             self.assertEqual(exc.filename, "/")