Adds an example pattern for canonical URLs.

Author: benjaoming

.readthedocs.yaml

@@ -11,16 +11,6 @@ version: 2
 #   tools:
 #     python: "3.10"
 
-# This pattern will be supported by a better environment variable, proposed
-# here: TBD
-build:
-  os: ubuntu-22.04
-  tools:
-    python: "3.10"
-  jobs:
-    pre_build:
-      - export "MKDOCS_SITE_URL=$READTHEDOCS_PROJECT"
-  
 mkdocs:
   configuration: mkdocs.yml
   fail_on_warning: true

mkdocs.yml

@@ -1,5 +1,9 @@
 site_name: Basic MkDocs Example Project
-site_url: !ENV MKDOCS_SITE_URL
+# Until https://github.com/readthedocs/readthedocs.org/issues/9781 is fixed, you need to
+# define CUSTOM_CANONICAL_URL yourself as a workaround.
+# (don't expose it to PRs, they build on different URLs)
+# For instance, define it as https://SLUG.readthedocs.io/en/stable/
+site_url: !ENV [READTHEDOCS_CANONICAL_URL, CUSTOM_CANONICAL_URL, ""]
 theme:
   name: readthedocs
   highlightjs: true