The filter manual is the docs tree's first FOLDER-index page: it serves
at /docs/user/filters while its nav entry carries /index
(/docs/user/filters/index). The sidebar's two checks — group expansion
(containsURL) and active-link styling (docsNavClass) — compared URLs
EXACTLY, so the folder URL matched neither: no submenu expansion, no
highlight (2026-11-01 user report: "the left sidebar should open to
the submenu and highlight the page").
Fix is structural, not per-page: both checks normalize folder-index
URLs (a trailing /index is the same page as its directory), so EVERY
folder-index page — current and future — expands and highlights like
a file page. No per-page registration exists anywhere in the docs
system to redo: the sidebar derives from the docs tree, and this was
the one URL shape its equality rule missed.
Pins: navigation (section + group expand for the folder URL, group
present) and docsNavClass (folder URL highlights the Overview item,
normalization symmetric, file pages keep their highlight, no
cross-highlighting).
John O'Keefe
0d613ba0e3