Subject: bug#71407: 30.0.50; Support arrays in json-ts-mode's imenu support

From: Tassilo Horn <[email-masked]>
Date: Fri, 07 Jun 2024 09:16:34 +0200

json-ts-mode adds imenu support for JSON files which is quite handy.
However, it doesn't support arrays (e.g., [...]) which reduces its
utility quite a bit.

Here is an example JSON file with an array:

--8<---------------cut here---------------start------------->8---
{
  "root": [
    {
      "foo": 1,
      "bar": "test1"
    },
    {
      "foo": 2,
      "bar": "test2"
    }
  ]
}
--8<---------------cut here---------------end--------------->8---

The Imenu *Completions* buffer with imenu-flatten set to t is:

--8<---------------cut here---------------start------------->8---
Click or type M-RET on a completion to select it.
Type M-<down> or M-<up> to move point between completions.

6 possible completions:
*Rescan* 	root:. 	root:bar
root:foo
--8<---------------cut here---------------end--------------->8---

Aha aha, 6 completions but only 4 are displayed because root:foo and
root:bar are basically there twice:

--8<---------------cut here---------------start------------->8---
imenu--index-alist is a variable defined in ‘imenu.el’.

Its value is
(("root" (" " . #<marker at 5 in test.json>)
  ("foo" . #<marker at 27 in test.json>)
  ("bar" . #<marker at 43 in test.json>)
  ("foo" . #<marker at 77 in test.json>)
  ("bar" . #<marker at 93 in test.json>)))
Local in buffer test.json; global value is nil
--8<---------------cut here---------------end--------------->8---

Well, but even if they were displayed twice, I wouldn't be able to know
which leads to the first and which to the second object's foo or bar.

In an ideal world, arrays would produce numerically indexed intermediate
nodes, e.g., I would have

  root:[0]:foo
  root:[0]:bar
  root:[1]:foo
  root:[1]:bar

Is that feasible?  AFAICS, the only Imenu thing json-ts-mode does is
defining

    ;; Imenu.
    (setq-local treesit-simple-imenu-settings
                '((nil "\\`pair\\'" nil nil)))

In GNU Emacs 30.0.50 (build 17, x86_64-pc-linux-gnu, GTK+ Version
 3.24.42, cairo version 1.18.0) of 2024-06-07 built on thinkpad-t440p
Repository revision: 6906ed28f1b4ac0cf0a2a725e7402290f33c26e2
Repository branch: master
System Description: Arch Linux

Configured using:
 'configure --with-tree-sitter --with-pgtk --with-modules'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
LCMS2 LIBOTF LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY
PDUMPER PGTK PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XIM GTK3 ZLIB

Important settings:
  value of $LC_MONETARY: de_DE.utf8
  value of $LC_NUMERIC: de_DE.utf8
  value of $LC_TIME: de_DE.utf8
  value of $LANG: en_US.UTF-8
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Major mode: ELisp/l

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  auto-composition-mode: t
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  auto-compression-mode: t

Load-path shadows:
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~/Repos/el/mu/mu4e/mu4e-mime-parts hides ~/Repos/el/mu/build/mu4e/mu4e-mime-parts
/home/horn/.emacs.d/elpa/ef-themes-1.7.0/theme-loaddefs hides /home/horn/Repos/el/emacs/lisp/theme-loaddefs
/home/horn/.emacs.d/elpa/transient-20240603.2200/transient hides /home/horn/Repos/el/emacs/lisp/transient

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