Ensure to define functions before calling them

README.org

@@ -196,8 +196,9 @@ that *Emacs is a self-documenting editor.*
 :CUSTOM_ID: sec:init-file-header
 :END:
 
-The =user-init-file= header requires =cl-lib= and customizes Emacs variables.
-It consists of four parts in listing [[lst:1st-custom-set-variables-call]],
+The =user-init-file= header requires =cl-lib=, backports new functions in
+Emacs-29.1 to Emacs-28.2, and customizes Emacs variables.  It consists of five
+parts in listing [[lst:backport-header]], [[lst:1st-custom-set-variables-call]],
 [[lst:2nd-custom-set-variables-call]], [[lst:3rd-custom-set-variables-call]], and
 [[lst:4th-custom-set-variables-call]] in order to limit the length of the listings
 for exporting to LaTeX.
@@ -213,15 +214,49 @@ example]].
 The [[info:emacs#Init File][init file (info)]] does not load the ~custom-file~ as [[info:emacs#Saving Customizations][saving customizations
 (info)]] recommends because of the ~custom-set-variables~ function calls.
 
-#+caption[Customize the first set of Emacs variables]:
-#+caption: Customize the first set of Emacs variables.
-#+name: lst:1st-custom-set-variables-call
+#+caption[Header with backport of Emacs-29.1 functionality]:
+#+caption: Header with backport of Emacs-29.1 functionality.
+#+name: lst:backport-header
 #+begin_src emacs-lisp
 ;;; init.el --- user init file                    -*- lexical-binding: t -*-
 ;;; Commentary:
 ;;; Code:
 (require 'cl-lib)
 
+(when (version< emacs-version "29.0.0")
+  (defmacro setopt (&rest pairs)
+    "Set VARIABLE/VALUE pairs, and return the final VALUE.
+This is like `setq', but is meant for user options instead of
+plain variables.  This means that `setopt' will execute any
+`custom-set' form associated with VARIABLE.
+
+\(fn [VARIABLE VALUE]...)"
+    (declare (debug setq))
+    (unless (zerop (mod (length pairs) 2))
+      (error "PAIRS must have an even number of variable/value members"))
+    (let ((expr nil))
+      (while pairs
+        (unless (symbolp (car pairs))
+          (error "Attempting to set a non-symbol: %s" (car pairs)))
+        (push `(setopt--set ',(car pairs) ,(cadr pairs))
+              expr)
+        (setq pairs (cddr pairs)))
+      (macroexp-progn (nreverse expr))))
+
+  (defun setopt--set (variable value)
+    (custom-load-symbol variable)
+    ;; Check that the type is correct.
+    (when-let ((type (get variable 'custom-type)))
+      (unless (widget-apply (widget-convert type) :match value)
+        (warn "Value `%S' does not match type %s" value type)))
+    (put variable 'custom-check-value (list value))
+    (funcall (or (get variable 'custom-set) #'set-default) variable value)))
+#+end_src
+
+#+caption[Customize the first set of Emacs variables]:
+#+caption: Customize the first set of Emacs variables.
+#+name: lst:1st-custom-set-variables-call
+#+begin_src emacs-lisp
 (custom-set-variables
  '(after-save-hook #'executable-make-buffer-file-executable-if-script-p)
  '(column-number-mode t)
@@ -259,7 +294,7 @@ The [[info:emacs#Init File][init file (info)]] does not load the ~custom-file~ a
    `,(delq nil `((auctex . "gnu")
                  (compat . "gnu")
                  (consult . "gnu-devel")
-                 ,(when (version< emacs-version "28.9.9")
+                 ,(when (version< emacs-version "29.0.0")
                     '(eglot . "gnu-devel"))
                  (embark . "gnu-devel")
                  (embark-consult . "gnu-devel")
@@ -365,9 +400,6 @@ the contents of packages and allows to update packages to the latest version.
         (package-install desc 'dont-select)))
     ;; Shadow built-in `org' by installing `org'.
     (shadow-builtin-by-install 'org)
-    ;; Shadow built-in `python' by installing `python'.
-    (when (version< emacs-version "28.9.9")
-      (shadow-builtin-by-install 'python))
     ;; Install the selected packages.
     (package-install-selected-packages)))
 
@@ -1438,7 +1470,6 @@ function [[info:elisp#Minibuffer Completion][completing-read]].  Listing [[lst:c
 |-----------------------------+----------------------+---------------------|
 | command                     | key map              | keys                |
 |-----------------------------+----------------------+---------------------|
-| consult-apropos             | help-map             | {{{kbd(<help> a)}}} |
 | consult-bookmark            | ctl-x-r-keymap       | {{{kbd(C-x r b)}}}  |
 | consult-buffer-other-frame  | ctl-x-5-keymap       | {{{kbd(C-x 5 b)}}}  |
 | consult-buffer-other-window | ctl-x-4-keymap       | {{{kbd(C-x 4 b)}}}  |
@@ -2095,7 +2126,10 @@ follows a list detailing and motivating each listing:
                  ,(when (fboundp 'maxima-mode) '(maxima . t))
                  (org . t)
                  (perl . t)
-                 (python . t)
+                 ;; The next two functions are not bound during bootstrap.
+                 ,(when (and (fboundp 'choose-common-python-interpreter)
+                             (fboundp 'choose-common-python-linter))
+                    '(python . t))
                  (shell . t))))
    '(org-export-backends '(ascii beamer html icalendar latex odt texinfo))
    '(org-file-apps '((auto-mode . emacs)
@@ -2346,7 +2380,7 @@ else:
   unicode=true,
   urlcolor=blue,
 }\n")
-   `,(if (version< emacs-version "28.9.9")
+   `,(if (version< emacs-version "29.0.0")
          '(org-latex-listings 'minted)
        '(org-latex-src-block-backend 'minted))
    '(org-latex-minted-langs '((cc "c++")
@@ -3947,7 +3981,7 @@ mode independent [[https://github.com/joaotavora/eglot][Eglot]] configuration:
 #+name: lst:minimal-eglot-setup
 #+begin_src emacs-lisp
 (with-eval-after-load 'emacs
-  (when (version< emacs-version "28.9.9")
+  (when (version< emacs-version "29.0.0")
     (ensure-package-installation 'eglot))
 
   ;; Replace `nil' with `t' for debugging.
@@ -4297,10 +4331,7 @@ src_emacs-lisp{(describe-function 'inferior-emacs-lisp-mode)}.
 #+name: lst:setup-ielm
 #+begin_src emacs-lisp
 (with-eval-after-load 'ielm
-  (if (version< "29.0.0" emacs-version)
-      (setopt ielm-dynamic-return nil)
-    (custom-set-variables
-     '(ielm-dynamic-return nil))))
+  (setopt ielm-dynamic-return nil))
 #+end_src
 
 ** [[https://fennel-lang.org/][Fennel Programming]]
@@ -4463,18 +4494,6 @@ rules which make [[https://flake8.pycqa.org/en/latest/][flake8]] or [[https://py
 Finally, listing [[lst:flake8-nocolor][flake8-nocolor]] and [[lst:ruff-nocolor][ruff-nocolor]] pipe the =stdout= output of the
 [[https://pypi.org/project/flake8/][flake8]] and [[https://pypi.org/project/ruff/][ruff]] executables through =cat= to remove escape sequences.
 
-#+caption[Setup Python mode]:
-#+caption: Setup Python mode.
-#+name: lst:setup-python-mode
-#+begin_src emacs-lisp
-(with-eval-after-load 'python
-  (custom-set-variables
-   '(python-indent-guess-indent-offset nil)
-   '(python-shell-completion-native-disabled-interpreters '("ipython3" "pypy")))
-  (choose-common-python-interpreter 'python)
-  (choose-common-python-linter 'ruff-nocolor))
-#+end_src
-
 #+caption[Choose a common Python interpreter]:
 #+caption: Choose a common Python interpreter for =ob-python= and =python-mode=.
 #+name: lst:choose-common-python-interpreter
@@ -4556,6 +4575,18 @@ Finally, listing [[lst:flake8-nocolor][flake8-nocolor]] and [[lst:ruff-nocolor][
                python-check-command python-flymake-command))))
 #+end_src
 
+#+caption[Setup Python mode]:
+#+caption: Setup Python mode.
+#+name: lst:setup-python-mode
+#+begin_src emacs-lisp
+(with-eval-after-load 'python
+  (custom-set-variables
+   '(python-indent-guess-indent-offset nil)
+   '(python-shell-completion-native-disabled-interpreters '("ipython3" "pypy")))
+  (choose-common-python-interpreter 'python)
+  (choose-common-python-linter 'ruff-nocolor))
+#+end_src
+
 #+caption[Access =pyenv=]:
 #+caption: Access =pyenv=.
 #+name: lst:access-pyenv