bug#59945: [PATCH] Fix empty pairs in js tree-sitter imenu alist

["Charl P. Botha" <cpbotha@vxlabs.com>]

The current js--treesit-imenu, used by the JavaScript, TypeScript and
TSX tree-sitter modes, would return empty pairs in the imenu alist if
there were none of that type of symbol.

This would break both the built in imenu and also packages like
consult-imenu.

See https://github.com/minad/consult/issues/697 for the discussion there.
---
 lisp/progmodes/js.el | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/lisp/progmodes/js.el b/lisp/progmodes/js.el
index 45dfef372cd..6ca260ad8ad 100644
--- a/lisp/progmodes/js.el
+++ b/lisp/progmodes/js.el
@@ -3732,10 +3732,17 @@ js--treesit-imenu
          (func-tree (treesit-induce-sparse-tree
                      node "function_declaration" nil 1000))
          (var-tree (treesit-induce-sparse-tree
-                    node "lexical_declaration" nil 1000)))
-    `(("Class" . ,(js--treesit-imenu-1 class-tree))
-      ("Variable" . ,(js--treesit-imenu-1 var-tree))
-      ("Function" . ,(js--treesit-imenu-1 func-tree)))))
+                    node "lexical_declaration" nil 1000))
+         (imenu-alist nil))
+    ;; when a sub-tree is empty, we should not return that pair at all
+    ;; https://github.com/minad/consult/issues/697#issuecomment-1345302734
+    (when func-tree
+      (setq imenu-alist (cons `("Function" . ,(js--treesit-imenu-1 func-tree)) imenu-alist)))
+    (when var-tree
+      (setq imenu-alist (cons `("Variable" . ,(js--treesit-imenu-1 var-tree)) imenu-alist)))
+    (when class-tree
+      (setq imenu-alist (cons `("Class" . ,(js--treesit-imenu-1 class-tree)) imenu-alist)))
+    imenu-alist))

 ;;; Main Function

--
2.25.1