bug#60407: [PATCH] Update go-ts-mode to use Imenu facility

[Evgeni Kolev <evgenysw@gmail.com>]

As I mentioned in the start of the mail thread - go-ts-mode's Imenu
puts Go interfaces and structs in the same "Type" bucket. This can be
improved in go-ts-mode.

I'm providing a second patch below which splits the interfaces and
structs into their own Imenu categories.

Please let me know if I should provide the second patch later, in a
separate thread, after the first patch is finished. I'm assuming it's
simpler to review the patches together. If it's not - I'll provide
them in a way to make the review easier, just let me know.

The second patch is below.

commit a5c4a0b25e0385516ad1f8c3444830111d467843
Author: Evgeni Kolev <evgenysw@gmail.com>
Date:   Sun Jan 1 18:57:26 2023 +0200

    Improve go-ts-mode Imenu

    go-ts-mode Imenu is improved to distinguish between Go interfaces and
    structs. Previously both were put in "Type" category. Now each has its
    own category: "Interface" and "Struct" respectively.

    * lisp/progmodes/go-ts-mode.el (go-ts-mode--interface-node-p)
    (go-ts-mode--struct-node-p): New functions.

diff --git a/lisp/progmodes/go-ts-mode.el b/lisp/progmodes/go-ts-mode.el
index c6c1c61d9f4..cb8d740727a 100644
--- a/lisp/progmodes/go-ts-mode.el
+++ b/lisp/progmodes/go-ts-mode.el
@@ -194,13 +194,14 @@ go-ts-mode
     (setq-local treesit-defun-type-regexp
                 (regexp-opt '("method_declaration"
                               "function_declaration"
-                              "type_spec")))
+                              "type_declaration")))
     (setq-local treesit-defun-name-function #'go-ts-mode--defun-name)

     ;; Imenu.
     (setq-local treesit-simple-imenu-settings
                 `(("Function" "\\`function_declaration\\'" nil nil)
-                  ("Type" "\\`type_spec\\'" nil nil)
+                  ("Interface" "\\`type_declaration\\'"
go-ts-mode--interface-node-p nil)
+                  ("Struct" "\\`type_declaration\\'"
go-ts-mode--struct-node-p nil)
                   ("Method" "\\`method_declaration\\'" nil nil)))

     ;; Indent.
@@ -223,13 +224,30 @@ go-ts-mode--defun-name
 Return nil if there is no name or if NODE is not a defun node."
   (pcase (treesit-node-type node)
     ((or "function_declaration"
-         "method_declaration"
-         "type_spec")
+         "method_declaration")
      (treesit-node-text
       (treesit-node-child-by-field-name
        node "name")
+      t))
+    ((or "type_declaration")
+     (treesit-node-text
+      (treesit-node-child-by-field-name
+       (treesit-node-child node 0 t) "name")
       t))))

+(defun go-ts-mode--interface-node-p (node)
+  "Return t if NODE is a Go interface."
+  (string-equal "interface_type"
+                (treesit-node-type
+                 (treesit-node-child-by-field-name
+                  (treesit-node-child node 0 t) "type"))))
+
+(defun go-ts-mode--struct-node-p (node)
+  "Return t if NODE is a Go struct"
+  (string-equal "struct_type" (treesit-node-type
+                               (treesit-node-child-by-field-name
+                                (treesit-node-child node 0 t) "type"))))
+
 ;; go.mod support.

 (defvar go-mod-ts-mode--syntax-table

On Sun, Jan 1, 2023 at 3:05 PM Evgeni Kolev <evgenysw@gmail.com> wrote:
>
> To illustrate the change, here's a comparison before VS after (VS eglot).
>
> I'm using a sample .go file (at the bottom of this mail).
>
> Before:
>      4 candidates:
>          Function: measure
>          Type: geometry
>          Type: rect
>          Type: circle
>
> After:
>      8 candidates:
>          Function: measure
>          Type: geometry
>          Type: rect
>          Type: circle
>          Method: area
>          Method: perim
>          Method: area
>          Method: perim
>
> For comparison, here's eglot's Imenu (using Go's gopls language server):
>      13 candidates:
>          Interface: geometry
>          Struct: rect
>          Struct: circle
>          Field.rect: width
>          Field.rect: height
>          Field.circle: radius
>          Method.geometry: area
>          Method.geometry: perim
>          Method: (rect).area
>          Method: (rect).perim
>          Method: (circle).area
>          Method: (circle).perim
>          Function: measure
>
> Sample .go file:
>
> > type geometry interface {
> >     area() float64
> >     perim() float64
> > }
> >
> > type rect struct {
> >     width, height float64
> > }
> >
> > type circle struct {
> >     radius float64
> > }
> >
> > func (r rect) area() float64 {
> >     return r.width * r.height
> > }
> >
> > func (r rect) perim() float64 {
> >     return 2*r.width + 2*r.height
> > }
> >
> > func (c circle) area() float64 {
> >     return math.Pi * c.radius * c.radius
> > }
> >
> > func (c circle) perim() float64 {
> >     return 2 * math.Pi * c.radius
> > }
> >
> > func measure(g geometry) {
> >     fmt.Println(g)
> >     fmt.Println(g.area())
> >     fmt.Println(g.perim())
> > }
>
> On Sun, Jan 1, 2023 at 11:07 AM Eli Zaretskii <eliz@gnu.org> wrote:
> >
> > > From: Evgeni Kolev <evgenysw@gmail.com>
> > > Date: Thu, 29 Dec 2022 18:05:49 +0200
> > >
> > > This patch updates go-ts-mode to use Imenu facility added in
> > > https://git.savannah.gnu.org/cgit/emacs.git/commit/?h=emacs-29&id=b39dc7ab27a696a8607ab859aeff3c71509231f5
> > >
> > > The Imenu items are extended to support "Method", in addition to
> > > "Function" and "Type".
> > >
> > > The current Imenu approach uses "type_spec" to identify "Type" which
> > > acts as a catch-all for many Go constructs, for example struct and
> > > interface definitions. This catch-all approach is not optimal because
> > > structs and interfaces are put in the same "Type" bucket. In a
> > > follow-up patch I'll try to change the approach and have separate
> > > "Interface" and "Struct" types.
> > >
> > > The patch is below.
> >
> > Randy, Yuan, are you looking into this?
> >
> > > commit 71ff7b21fe92167313bd1761b68b6e6fd879b09f
> > > Author: Evgeni Kolev <evgenysw@gmail.com>
> > > Date:   Thu Dec 29 17:49:40 2022 +0200
> > >
> > >     Update go-ts-mode to use Imenu facility
> > >
> > >     go-ts-mode is updated to use the Imenu facility added in commit
> > >     b39dc7ab27a696a8607ab859aeff3c71509231f5.
> > >
> > >     The Imenu items are extended to support "Method", in addition to
> > >     "Function" and "Type".
> > >
> > >     * lisp/progmodes/go-ts-mode.el (go-ts-mode--imenu-1) (go-ts-mode--imenu):
> > >     Remove functions.
> > >     (go-ts-mode--defun-name): New function.
> > >
> > > diff --git a/lisp/progmodes/go-ts-mode.el b/lisp/progmodes/go-ts-mode.el
> > > index 124d9b044a2..c6c1c61d9f4 100644
> > > --- a/lisp/progmodes/go-ts-mode.el
> > > +++ b/lisp/progmodes/go-ts-mode.el
> > > @@ -173,44 +173,6 @@ go-ts-mode--font-lock-settings
> > >     '((ERROR) @font-lock-warning-face))
> > >    "Tree-sitter font-lock settings for `go-ts-mode'.")
> > >
> > > -(defun go-ts-mode--imenu ()
> > > -  "Return Imenu alist for the current buffer."
> > > -  (let* ((node (treesit-buffer-root-node))
> > > -         (func-tree (treesit-induce-sparse-tree
> > > -                     node "function_declaration" nil 1000))
> > > -         (type-tree (treesit-induce-sparse-tree
> > > -                     node "type_spec" nil 1000))
> > > -         (func-index (go-ts-mode--imenu-1 func-tree))
> > > -         (type-index (go-ts-mode--imenu-1 type-tree)))
> > > -    (append
> > > -     (when func-index `(("Function" . ,func-index)))
> > > -     (when type-index `(("Type" . ,type-index))))))
> > > -
> > > -(defun go-ts-mode--imenu-1 (node)
> > > -  "Helper for `go-ts-mode--imenu'.
> > > -Find string representation for NODE and set marker, then recurse
> > > -the subtrees."
> > > -  (let* ((ts-node (car node))
> > > -         (children (cdr node))
> > > -         (subtrees (mapcan #'go-ts-mode--imenu-1
> > > -                           children))
> > > -         (name (when ts-node
> > > -                 (treesit-node-text
> > > -                  (pcase (treesit-node-type ts-node)
> > > -                    ("function_declaration"
> > > -                     (treesit-node-child-by-field-name ts-node "name"))
> > > -                    ("type_spec"
> > > -                     (treesit-node-child-by-field-name ts-node "name"))))))
> > > -         (marker (when ts-node
> > > -                   (set-marker (make-marker)
> > > -                               (treesit-node-start ts-node)))))
> > > -    (cond
> > > -     ((or (null ts-node) (null name)) subtrees)
> > > -     (subtrees
> > > -      `((,name ,(cons name marker) ,@subtrees)))
> > > -     (t
> > > -      `((,name . ,marker))))))
> > > -
> > >  ;;;###autoload
> > >  (add-to-list 'auto-mode-alist '("\\.go\\'" . go-ts-mode))
> > >
> > > @@ -228,9 +190,18 @@ go-ts-mode
> > >      (setq-local comment-end "")
> > >      (setq-local comment-start-skip (rx "//" (* (syntax whitespace))))
> > >
> > > +    ;; Navigation.
> > > +    (setq-local treesit-defun-type-regexp
> > > +                (regexp-opt '("method_declaration"
> > > +                              "function_declaration"
> > > +                              "type_spec")))
> > > +    (setq-local treesit-defun-name-function #'go-ts-mode--defun-name)
> > > +
> > >      ;; Imenu.
> > > -    (setq-local imenu-create-index-function #'go-ts-mode--imenu)
> > > -    (setq-local which-func-functions nil)
> > > +    (setq-local treesit-simple-imenu-settings
> > > +                `(("Function" "\\`function_declaration\\'" nil nil)
> > > +                  ("Type" "\\`type_spec\\'" nil nil)
> > > +                  ("Method" "\\`method_declaration\\'" nil nil)))
> > >
> > >      ;; Indent.
> > >      (setq-local indent-tabs-mode t
> > > @@ -247,6 +218,18 @@ go-ts-mode
> > >
> > >      (treesit-major-mode-setup)))
> > >
> > > +(defun go-ts-mode--defun-name (node)
> > > +  "Return the defun name of NODE.
> > > +Return nil if there is no name or if NODE is not a defun node."
> > > +  (pcase (treesit-node-type node)
> > > +    ((or "function_declaration"
> > > +         "method_declaration"
> > > +         "type_spec")
> > > +     (treesit-node-text
> > > +      (treesit-node-child-by-field-name
> > > +       node "name")
> > > +      t))))
> > > +
> > >  ;; go.mod support.
> > >
> > >  (defvar go-mod-ts-mode--syntax-table
> > >
> > >
> > >
> > >