hamacs/ha-programming-elisp.org

#+TITLE:  Emacs Lisp Configuration
#+AUTHOR: Howard X. Abrams
#+DATE:   2022-05-11

A literate programming file for configuring Emacs for Lisp programming.

#+begin_src emacs-lisp :exports none
  ;;; ha-lisp --- configuring Emacs for Lisp programming. -*- lexical-binding: t; -*-
  ;;
  ;; © 2022-2023 Howard X. Abrams
  ;;   Licensed under a Creative Commons Attribution 4.0 International License.
  ;;   See http://creativecommons.org/licenses/by/4.0/
  ;;
  ;; Author: Howard X. Abrams <http://gitlab.com/howardabrams>
  ;; Maintainer: Howard X. Abrams
  ;; Created: May 11, 2022
  ;;
  ;; This file is not part of GNU Emacs.
  ;;
  ;; *NB:* Do not edit this file. Instead, edit the original literate file at:
  ;;            /Users/howard.abrams/other/hamacs/ha-lisp.org
  ;;       And tangle the file to recreate this one.
  ;;
  ;;; Code:
  #+end_src
* Introduction
While I program in a lot of languages, I seem to be writing all my helper tools and scripts in … Emacs Lisp. I’m cranking this up to 11.

New, /non-literal/ source code comes from [[file:templates/emacs-lisp-mode.el][emacs-lisp-mode template]]:
#+begin_src emacs-lisp
  (ha-auto-insert-file (rx ".el" eol) "emacs-lisp-mode.el")
#+end_src

Perhaps we should have an Emacs Lisp-specific leader for advanced commands:
#+begin_src emacs-lisp
  (general-create-definer ha-elisp-leader
      :states '(normal visual motion)
      :keymaps '(emacs-lisp-mode-map lisp-mode-map)
      :prefix ","
      :global-prefix "<f17>"
      :non-normal-prefix "S-SPC")
#+end_src
* Syntax Display
** Dim those Parenthesis
The [[https://github.com/tarsius/paren-face][paren-face]] project lowers the color level of parenthesis which I find better.

#+begin_src emacs-lisp
  (use-package paren-face
    :hook (emacs-lisp-mode . paren-face-mode))
#+end_src

Show code examples with the [[https://github.com/xuchunyang/elisp-demos][elisp-demos]] package.
#+begin_src emacs-lisp
  (use-package elisp-demos
    :config
    (advice-add 'describe-function-1 :after #'elisp-demos-advice-describe-function-1))
#+end_src
** Better Function Help
Let’s take advantage of [[https://github.com/Wilfred/helpful][helpful]] package for getting more information into the =describe-function= call.
#+begin_src emacs-lisp
  (use-package helpful)
#+end_src
And we should extend it with the [[https://github.com/xuchunyang/elisp-demos][elisp-demos]] project:
#+begin_src emacs-lisp
  (use-package elisp-demos
    :after helpful
    :config
    (ha-elisp-leader
      "h a" '("add helpful demo" . elisp-demos-add-demo))

    (advice-add 'helpful-update :after #'elisp-demos-advice-helpful-update))
#+end_src
Find a function without a good demonstration? Call =elisp-demos-add-demo=.
* Navigation and Editing
** Goto Definitions
Wilfred’s [[https://github.com/Wilfred/elisp-def][elisp-def]] project does a better job at jumping to the definition of a symbol at the point, so:
#+begin_src emacs-lisp
  (use-package elisp-def
    :hook (emacs-lisp-mode . elisp-def-mode))
#+end_src
This /should work/ with [[help:evil-goto-definition][evil-goto-defintion]], as that calls this list from [[help:evil-goto-definition-functions][evil-goto-definition-functions]]:
  - [[help:evil-goto-definition-imenu][evil-goto-definition-imenu]]
  - [[help:evil-goto-definition-semantic][evil-goto-definition-semantic]]
  - [[help:evil-goto-definition-xref][evil-goto-definition-xref]] … to show what calls a function
  - [[help:evil-goto-definition-search][evil-goto-definition-search]]

While I love packages that add functionality and I don’t have to learn anything, I’m running into an issue where I do a lot of my Emacs Lisp programming in org files, and would like to jump to the function definition /defined in the org file/. Since [[https://github.com/BurntSushi/ripgrep][ripgrep]] is pretty fast, I’ll call it instead of attempting to build a [[https://stackoverflow.com/questions/41933837/understanding-the-ctags-file-format][CTAGS]] table. Oooh, the =rg= takes a =—json= option, which makes it easier to parse.

#+begin_src emacs-lisp
  (defun ha-org-code-block-jump (str pos)
    "Go to a literate org file containing a symbol, STR.
  The POS is ignored."
    ;; Sometimes I wrap a function name in `=' characters, and these should be removed:
    (when (string-match (rx "=" (group (one-or-more any)) "=") str)
      (setq str (match-string 1 str)))
    (ignore-errors
      (let* ((default-directory (projectile-project-root))
             (command (format "rg --json '\\(def[^ ]+ %s ' *.org" str))
             (results (thread-last command
                                   shell-command-to-list
                                   second
                                   json-parse-string))
             (file    (thread-last results
                                   (gethash "data")
                                   (gethash "path")
                                   (gethash "text")))
             (line    (thread-last results
                                   (gethash "data")
                                   (gethash "line_number"))))
        (find-file file)
        (goto-line line))))

  (add-to-list 'evil-goto-definition-functions 'ha-org-code-block-jump)
#+end_src
** Lispy
I like the idea of [[https://github.com/abo-abo/lispy][lispy]] for making a Lisp-specific /keybinding state/ (similar to Evil).

My primary use-case is for its refactoring and other unique features. For instance, I love [[help:lispy-ace-paren][lispy-ace-paren]] that puts an /ace label/ on every parenthesis, allowing me to quickly jump to any s-expression.

#+begin_src emacs-lisp
  (use-package lispy
    :config
    (evil-define-key 'normal emacs-lisp-mode-map
      "gf" 'lispy-ace-paren
      "gF" 'lispy-ace-symbol)

    (ha-elisp-leader
      "r i" '("cond→if" . lispy-to-ifs)
      "r c" '("if→cond" . lispy-to-cond)
      "r d" '("λ→𝑓" . lispy-to-defun)
      "r l" '("𝑓→λ" . lispy-to-lambda)
      "r f" '("flatten" . lispy-flatten)
      "r b" '("bind var" . lispy-bind-variable)
      "r u" '("unbind var" . lispy-unbind-variable)

      "e d" '("edebug" . lispy-edebug)
      "e j" '("debug-step-in" . lispy-debug-step-in)
      "e R" '("eval-and-replace" . lispy-eval-and-replace)

      "h d" '("describe" . lispy-describe)
      "t t" '("ert" . lispy-ert)))
#+end_src
** Lispyville
I want an Evil version of [[Lispy]]. The [[https://github.com/noctuid/lispyville][lispyville project]] builds on it to make it Evil. From the README:
#+begin_quote
The main difference from an evil state is that lispy’s “special” is contextually based on the point (special is when the point is before an opening delimiter, after a closing delimiter, or when there is an active region).
#+end_quote

Many of the operations supplied by =lispyville= don’t require learning anything new. Similar to [[Clever Parenthesis]], we can
For instance, if our point is placed at this location in this code:
#+begin_src emacs-lisp
  (message "The answer is %d" (+ 2 (* 8 5)‸ 9 (+ 1 4)))
#+end_src
Pressing ~D~ results in:
#+begin_src emacs-lisp
  (message "The answer is %d" (+ 2 (* 8 5)‸))
#+end_src
And doesn’t delete the trailing parenthesis.

The /trick/ to being effective with the [[https://www.emacswiki.org/emacs/ParEdit][paredit-family]] of extensions is learning the keys. The killer “app” is the slurp/barf sequence. Use the ~<~ key, in normal mode, to barf (or jettison)… in other words, /move/ the paren closer to the point. For instance:
#+begin_src emacs-lisp :tangle no
  (+ 41 (* ‸1 3))  ⟹  (+ 41 (* ‸1) 3)
#+end_src
Use the ~>~ key to /slurp/ in outside objects into the current expression… in other words, move the paren away from the point. For instance:
#+begin_src emacs-lisp :tangle no
  (+ 41 (* ‸1) 3)  ⟹  (+ 41 (* ‸1 3))
#+end_src

*Note:* I used to use the [[https://github.com/luxbock/evil-cleverparens][evil-cleverparens]] project to have similar keybindings but in all programming languages. I found that =lispyville= is a little more reliable, and that I don’t really use these types of code manipulation in my day-job programming languages of Python and YAML.

#+begin_src emacs-lisp
  (use-package lispyville
    :after lispy
    :hook ((emacs-lisp-mode-hook lisp-mode-hook) . lispyville-mode)

    :config
    (lispyville-set-key-theme '(operators atom-movement
                                commentary slurp/barf-lispy additional-wrap
                                additional additional-insert))

    (evil-define-key '(normal insert emacs) lispyville-mode-map
      (kbd "M-h") 'lispyville-beginning-of-defun
      (kbd "M-l") 'lispyville-beginning-of-next-defun
      (kbd "M-i") 'lispyville-insert-at-beginning-of-list ; These are useful
      (kbd "M-a") 'lispyville-insert-at-end-of-list       ; and I want to use
      (kbd "M-o") 'lispyville-open-below-list             ; these in insert
      (kbd "M-O") 'lispyville-open-above-list             ; or Emacs state.

      ;; The c-w theme is VI-specific. I still use Emacs' M-Delete:
      (kbd "M-DEL")  'lispyville-delete-backward-word)

    ;; Sentence and paragraph movement doesn't make sense in a Lisp world,
    ;; so I redefine these based on my own personal expectations:
    (evil-define-key 'normal lispyville-mode-map
      "H" 'lispyville-backward-sexp-begin
      (kbd "M-H") 'lispyville-backward-sexp-end
      "L" 'lispyville-forward-sexp-begin
      (kbd "M-L") 'lispyville-forward-sexp-end
      "(" 'lispyville-previous-opening
      ")" 'lispyville-next-closing
      "{" 'lispyville-backward-up-list
      "}" 'lispyville-next-opening)

    ;; Visually high-light a region, just hit `(' to wrap it in parens.
    ;; Without smartparens, we need to insert a pair of delimiters:
    (evil-define-key '(visual insert emacs) lispyville-mode-map "(" 'lispy-parens)
    (evil-define-key '(visual insert emacs) lispyville-mode-map "[" 'lispy-brackets)
    (evil-define-key '(visual insert emacs) lispyville-mode-map "{" 'lispy-braces))
#+end_src

Instead of converting /all keybindings/, the project supplies /key themes/ to grab specific keybinding groups.
  - =operators= :: basic VI operators that keep stuff balanced
  - =c-w= :: replaces the ~C-w~, but since that is VI-specific, I rebind this to ~M-Delete~
  - =text-objects= :: Add more text-objects, I wrote my [[file:ha-config.org::*Better Parenthesis with Text Object][own version]] for s-expressions, but I might try these
  - =atom-movement= :: The ~e~ / ~w~ and ~b~ keys will move by /symbols/ instead of /words/.
  - =additional-movement= :: Adds new movement keys, ~H~ / ~L~ for s-expr and the ~(~ / ~)~ for getting to closest expressions. This doesn’t work well, but is easy to re-implement.
  - =commentary= :: Replace ~gc~ for un/commenting Lisp elements.
  - =slurp/bar-lispy= :: always allow ~<~ / ~>~ to slurp/barf even /inside/ an s-expression.
  - =additional= :: New ~M-~ bindings for manipulating s-expressions. ~M-J~ is very cool.
  - =additional-insert= :: ~M-i~ insert at beginning, and ~M-a~ to insert at the end of a list.
  - =wrap= :: like [[file:ha-config.org::*Evil Surround][Evil Surround]] but with one less keystroke. ~M-( M-(~ wraps the entire line.
  - =additional-wrap= :: is another version of the =wrap= that automatically wraps current symbol, and then you can slurp in the rest.
  - =mark= :: The ~v~ will highlight current symbol, and ~V~ will highlight current s-expression. Continues to work with [[file:ha-config.org::*Expand Region][Expand Region]].

New bindings to remember:
  - ~>~ :: slurp
  - ~<~ :: barf

  - ~H~ :: backward s-expression
  - ~L~ :: forward s-expression
  - ~M-h~ :: beginning of defun
  - ~M-l~ :: end of defun

  - ~M-i~ :: insert at beginning of list
  - ~M-a~ :: insert at end of list
  - ~M-o~ :: open below list … never worry about inserting into a bunch of closing parens.
  - ~M-O~ :: open above list

  - ~M-j~ :: drag forward
  - ~M-k~ :: drag backward
  - ~M-J~ :: join
  - ~M-s~ :: splice … I could use specific examples for these operations so I would know when to use them.
  - ~M-S~ :: split
  - ~M-r~ :: raise s-expression
  - ~M-R~ :: raise list
  - ~M-t~ :: transpose s-expressions
  - ~M-v~ :: convolute s-expression

These are all good, but the primary keys I need to figure out, are the s-expression movement keys:
  - ~{~ :: backward up list … nice to hit once (maybe twice), but isn’t something to use to navigate
  - ~}~ :: next opening parenthesis
  - ~(~ :: previous opening paren
  - ~)~ :: next closing parenthesis
** Eval Current Expression
The [[https://github.com/xiongtx/eros][eros]] package stands for Evaluation Result OverlayS for Emacs Lisp, and basically shows what each s-expression is near the cursor position instead of in the mini-buffer at the bottom of the window.
#+begin_src emacs-lisp
  (use-package eros
    :hook (emacs-lisp-mode . eros-mode))
#+end_src

A feature I enjoyed from Spacemacs is the ability to evaluate the s-expression currently containing the point. Not sure how they made it, but [[help:evil-cp-next-closing ][evil-cp-next-closing]] from cleverparens can help:

#+begin_src emacs-lisp
  (defun ha-eval-current-expression ()
    "Evaluates the expression the point is currently 'in'.
  It does this, by jumping to the end of the current
  expression (using evil-cleverparens), and evaluating what it
  finds at that point."
    (interactive)
    (save-excursion
      (unless (looking-at (rx (any ")" "]")))
        (lispyville-next-closing))
      (call-interactively 'eval-last-sexp)))
#+end_src

And we just need to bind it.
#+begin_src emacs-lisp
  (ha-prog-leader
    "e c" '("current" . ha-eval-current-expression))
#+end_src
* Technical Artifacts                                :noexport:
Let's =provide= a name so we can =require= this file:

#+begin_src emacs-lisp :exports none
  (provide 'ha-programming-elisp)
  ;;; ha-programming-elisp.el ends here
  #+end_src

#+DESCRIPTION: configuring Emacs for Lisp programming.

#+PROPERTY:    header-args:sh :tangle no
#+PROPERTY:    header-args:emacs-lisp  :tangle yes
#+PROPERTY:    header-args    :results none :eval no-export :comments no mkdirp yes

#+OPTIONS:     num:nil toc:nil todo:nil tasks:nil tags:nil date:nil
#+OPTIONS:     skip:nil author:nil email:nil creator:nil timestamp:nil
#+INFOJS_OPT:  view:nil toc:nil ltoc:t mouse:underline buttons:0 path:http://orgmode.org/org-info.js