Add imenu support

This is clashes with lsp-imenu if lsp is used,
which can be disabled with (setq lsp-enable-imenu nil)

Author: dgud

erlang-ts-imenu.el

@@ -0,0 +1,83 @@
+;;; erlang-ts-imenu.el --- imenu helpers -*- lexical-binding: t; -*-
+;; %CopyrightBegin%
+;;
+;; Copyright Ericsson AB 2024-2025. All Rights Reserved.
+;;
+;; Licensed under the Apache License, Version 2.0 (the "License");
+;; you may not use this file except in compliance with the License.
+;; You may obtain a copy of the License at
+;;
+;;     http://www.apache.org/licenses/LICENSE-2.0
+;;
+;; Unless required by applicable law or agreed to in writing, software
+;; distributed under the License is distributed on an "AS IS" BASIS,
+;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;; See the License for the specific language governing permissions and
+;; limitations under the License.
+;;
+;; %CopyrightEnd%
+;;
+
+;;; Commentary:
+;; Imenu functionality using treesitter
+;; Conflicts with lsp-imenu functionality if lsp is used
+;; lsp's imenu functionality can be disabled with:
+;; `(setq lsp-enable-imenu nil)`
+
+(require 'treesit)
+
+;;; Code:
+
+(defun erlang-ts-imenu-node-func-p (node)
+  "Check if NODE is the first function clause is the first."
+  (if (equal (treesit-node-type node) "fun_decl")
+      (when-let ((prev (treesit-node-prev-sibling node))
+                 (name (erlang-ts-imenu-func-name node)))
+        (not (and (equal (treesit-node-type prev) "fun_decl")
+                  (equal (erlang-ts-imenu-func-name prev) name))))
+    nil))
+
+(defun erlang-ts-imenu-func-name (node)
+  "Fetch function name at NODE."
+  (let ((clause (treesit-node-child-by-field-name node "clause")))
+    (concat (treesit-node-text (treesit-node-child-by-field-name clause "name"))
+            "/"
+            (number-to-string
+             (treesit-node-child-count
+              (treesit-node-child-by-field-name clause "args")
+              "args")))))
+
+(defun erlang-ts-imenu-pp-name (node)
+  "Fetch macro name at NODE."
+    (let ((lhs (treesit-node-child-by-field-name node "lhs")))
+      (let ((name (treesit-node-text (treesit-node-child-by-field-name lhs "name"))))
+        (if-let* ((args (treesit-node-child-by-field-name lhs "args")))
+            (concat name "/" (number-to-string (treesit-node-child-count args "args")))
+          name))))
+
+(defun erlang-ts-imenu-record-name (node)
+  "Fetch record name at NODE."
+  (let ((name (treesit-node-text (treesit-node-child-by-field-name node "name"))))
+    (concat "#" name "{}")))
+
+(defun erlang-ts-imenu-type-name (node)
+  "Fetch type name at NODE."
+  (let ((name (treesit-node-text
+               (treesit-node-child-by-field-name
+                (treesit-node-child-by-field-name node "name") "name"))))
+    name))
+
+(defun erlang-ts-imenu-setup ()
+  "Setup imenu functions."
+  (setq-local
+   treesit-simple-imenu-settings
+   '(
+     ("macros" "\\`pp_define\\'" nil erlang-ts-imenu-pp-name)
+     ("records" "\\`record_decl\\'" nil erlang-ts-imenu-record-name)
+     ("types" "\\`type_alias\\'" nil erlang-ts-imenu-type-name)
+     ("functions" "\\`fun_decl\\'" erlang-ts-imenu-node-func-p erlang-ts-imenu-func-name)
+     )))
+
+(provide 'erlang-ts-imenu)
+
+;;; erlang-ts-imenu.el ends here

erlang-ts.el

@@ -66,6 +66,7 @@
 
 (require 'treesit)
 (require 'erlang)
+(require 'erlang-ts-imenu)
 
 ;; Override erlang font-lock functions
 ;; So the menus (and functions) work as expected
@@ -441,6 +442,10 @@ NODE is the treesit node to process."
   (advice-add #'erlang-font-lock-level-3 :around #'erlang-ts--font-lock-level-3)
   (advice-add #'erlang-font-lock-level-4 :around #'erlang-ts--font-lock-level-4)
 
+  ;; This figths with lsp's imenu functionality if lsp is used
+  ;; Use (setq lsp-enable-imenu nil) to disable lsp-imenu
+  (erlang-ts-imenu-setup)
+
   (treesit-major-mode-setup)
   (setq-local syntax-propertize-function #'erlang-ts--syntax-propertize))