Addons + Proxito: return X-RTD-Resolver-Filename and inject via CF

Return `X-RTD-Resolver-Filename` from El Proxito and inject it as HTML `meta`
tag from Cloudflare Worker.

Required by readthedocs/addons#211

dockerfiles/force-readthedocs-addons.js

@@ -70,6 +70,7 @@ async function handleRequest(request) {
   // get project/version slug from headers inject by El Proxito
   const projectSlug = originalResponse.headers.get("x-rtd-project") || "";
   const versionSlug = originalResponse.headers.get("x-rtd-version") || "";
+  const resolverFilename = originalResponse.headers.get("x-rtd-resolver-filename") || "";
 
   // check to decide whether or not inject the new beta addons:
   //
@@ -103,7 +104,7 @@ async function handleRequest(request) {
           // .on(readthedocsDataParse, new removeElement())
           // .on(readthedocsData, new removeElement())
           .on("head", new addPreloads())
-          .on("head", new addProjectVersionSlug(projectSlug, versionSlug))
+          .on("head", new addMetaTags(projectSlug, versionSlug, resolverFilename))
           .transform(originalResponse)
       );
     }
@@ -116,7 +117,7 @@ async function handleRequest(request) {
     if (forceAddons === "false" && injectHostingIntegrations === "true") {
       return new HTMLRewriter()
         .on("head", new addPreloads())
-        .on("head", new addProjectVersionSlug(projectSlug, versionSlug))
+        .on("head", new addMetaTags(projectSlug, versionSlug, resolverFilename))
         .transform(originalResponse);
     }
   }
@@ -155,22 +156,25 @@ class addPreloads {
   }
 }
 
-class addProjectVersionSlug {
-  constructor(projectSlug, versionSlug) {
+class addMetaTags {
+  constructor(projectSlug, versionSlug, resolverFilename) {
     this.projectSlug = projectSlug;
     this.versionSlug = versionSlug;
+    this.resolverFilename = resolverFilename;
   }
 
   element(element) {
     console.log(
-      `addProjectVersionSlug. projectSlug=${this.projectSlug} versionSlug=${this.versionSlug}`,
+      `addMetaTags. projectSlug=${this.projectSlug} versionSlug=${this.versionSlug} resolverFilename=${this.resolverFilename}`,
     );
     if (this.projectSlug && this.versionSlug) {
       const metaProject = `<meta name="readthedocs-project-slug" content="${this.projectSlug}" />`;
       const metaVersion = `<meta name="readthedocs-version-slug" content="${this.versionSlug}" />`;
+      const metaResolverFilename = `<meta name="readthedocs-resolver-filename" content="${this.resolverFilename}" />`;
 
       element.append(metaProject, { html: true });
       element.append(metaVersion, { html: true });
+      element.append(metaResolverFilename, { html: true });
     }
   }
 }

dockerfiles/nginx/proxito.conf.template

@@ -75,6 +75,8 @@ server {
         add_header X-RTD-Project-Method $rtd_project_method always;
         set $rtd_redirect $upstream_http_x_rtd_redirect;
         add_header X-RTD-Redirect $rtd_redirect always;
+        set $rtd_resolver_filename $upstream_http_x_rtd_resolver_filename;
+        add_header X-RTD-Resolver-Filename $rtd_resolver_filename always;
         set $cdn_cache_control $upstream_http_cdn_cache_control;
         add_header CDN-Cache-Control $cdn_cache_control always;
         set $cache_tag $upstream_http_cache_tag;

readthedocs/proxito/middleware.py

@@ -23,9 +23,11 @@
 from readthedocs.core.unresolver import (
     InvalidCustomDomainError,
     InvalidExternalDomainError,
+    InvalidPathForVersionedProjectError,
     InvalidSubdomainError,
     InvalidXRTDSlugHeaderError,
     SuspiciousHostnameError,
+    unresolve,
     unresolver,
 )
 from readthedocs.core.utils import get_cache_tag
@@ -187,17 +189,19 @@ def add_cache_headers(self, request, response):
         else:
             cache_response(response, force=False)
 
-    def _set_request_attributes(self, request, unresolved_domain):
+    def _set_request_attributes(self, request, unresolved_domain, unresolved_url):
         """
         Set attributes in the request from the unresolved domain.
 
         - Set ``request.unresolved_domain`` to the unresolved domain.
         """
         request.unresolved_domain = unresolved_domain
+        request.unresolved_url = unresolved_url
 
     def process_request(self, request):  # noqa
         # Initialize our custom request attributes.
         request.unresolved_domain = None
+        request.unresolved_url = None
 
         skip = any(request.path.startswith(reverse(view)) for view in self.skip_views)
         if skip:
@@ -229,7 +233,12 @@ def process_request(self, request):  # noqa
         except InvalidXRTDSlugHeaderError as exc:
             raise SuspiciousOperation("Invalid X-RTD-Slug header.") from exc
 
-        self._set_request_attributes(request, unresolved_domain)
+        try:
+            unresolved_url = unresolve(request.build_absolute_uri())
+        except InvalidPathForVersionedProjectError:
+            unresolved_url = None
+
+        self._set_request_attributes(request, unresolved_domain, unresolved_url)
 
         response = self._get_https_redirect(request)
         if response:
@@ -367,11 +376,20 @@ def _get_https_redirect(self, request):
 
         return None
 
+    def add_resolver_headers(self, request, response):
+        # TODO: find a better way to re-use the unresolved URL so we don't
+        # query the db multiple times on the same request.
+        # https://github.com/readthedocs/readthedocs.org/issues/10456
+        if request.unresolved_url is not None:
+            # TODO: add more ``X-RTD-Resolver-*`` headers
+            response["X-RTD-Resolver-Filename"] = request.unresolved_url.filename
+
     def process_response(self, request, response):  # noqa
         self.add_proxito_headers(request, response)
         self.add_cache_headers(request, response)
         self.add_hsts_headers(request, response)
         self.add_user_headers(request, response)
         self.add_hosting_integrations_headers(request, response)
+        self.add_resolver_headers(request, response)
         self.add_cors_headers(request, response)
         return response