1 files changed, 30 insertions, 0 deletions
diff --git a/docs/extensions/canonical_fix.py b/docs/extensions/canonical_fix.py
new file mode 100644
index 0000000..509a546
--- /dev/null
+++ b/docs/extensions/canonical_fix.py
@@ -0,0 +1,30 @@
+from sphinx.application import Sphinx
+from sphinx.builders.dirhtml import DirectoryHTMLBuilder
+
+
+def setup(app: Sphinx):
+    app.connect("html-page-context", canonical_url)
+
+
+def canonical_url(app: Sphinx, pagename, templatename, context, doctree):
+    """Sphinx 1.8 builds a canonical URL if ``html_baseurl`` config is
+    set. However, it builds a URL ending with ".html" when using the
+    dirhtml builder, which is incorrect. Detect this and generate the
+    correct URL for each page.
+    Also accepts the custom, deprecated ``canonical_url`` config as the
+    base URL. This will be removed in version 2.1.
+    """
+    base = app.config.html_baseurl
+
+    if (
+        not base
+        or not isinstance(app.builder, DirectoryHTMLBuilder)
+        or not context["pageurl"]
+        or not context["pageurl"].endswith(".html")
+    ):
+        return
+
+    # Fix pageurl for dirhtml builder if this version of Sphinx still
+    # generates .html URLs.
+    target = app.builder.get_target_uri(pagename)
+    context["pageurl"] = base + target