fixing dirhtml builds

sphinx_book_theme/__init__.py

@@ -86,12 +86,17 @@ def find_url_relative_to_root(pagename, relative_page, path_docs_source):
 
     # Convert everything to paths for use later
     path_rel = Path(relative_page).with_suffix("")
-    path_parent = Path(pagename)  # pagename is relative to docs root
+    if relative_page.endswith(".html"):
+        # HTML file Sphinx builder
+        path_parent = Path(pagename).parent  # pagename is .html relative to docs root
+
+    else:
+        # DirHTML Sphinx builder.
+        path_parent = Path(pagename)  # pagename is the parent folder if dirhtml builder
+
     source_dir = Path(path_docs_source)
     # This should be the path to `relative_page`, relative to `pagename`
-    path_rel_from_page_dir = source_dir.joinpath(
-        path_parent.parent.joinpath(path_rel.parent)
-    )
+    path_rel_from_page_dir = source_dir.joinpath(path_parent.joinpath(path_rel.parent))
     path_from_page_dir = Path(os.path.abspath(path_rel_from_page_dir))
     page_rel_root = path_from_page_dir.relative_to(source_dir).joinpath(path_rel.name)
     return page_rel_root

tests/test_build.py

@@ -270,3 +270,11 @@ def test_missing_title(sphinx_build_factory):
     """Test building with a book w/ no title on the master page."""
     with pytest.raises(ThemeError, match="Landing page missing a title: index"):
         sphinx_build_factory("notitle").build()
+
+
+def test_docs_dirhtml(sphinx_build_factory):
+    """Test that builds with dirhtml pass without error."""
+    sphinx_build = sphinx_build_factory("base", buildername="dirhtml").build(
+        assert_pass=True
+    )
+    assert (sphinx_build.outdir / "index.html").exists(), sphinx_build.outdir.glob("*")