From 4af99998349705cc4ced90cdbf4f51455c51ec95 Mon Sep 17 00:00:00 2001
From: Bram Schoenmakers <me@bramschoenmakers.nl>
Date: Sun, 30 Jul 2023 21:27:19 +0200
Subject: [PATCH] Add gist to restrict commands to a certain major mode

---
 gists.org                               | 27 +++++++++++++++++++++++++
 gists/restrict-command-to-major-mode.el | 22 ++++++++++++++++++++
 2 files changed, 49 insertions(+)
 create mode 100644 gists/restrict-command-to-major-mode.el

diff --git a/gists.org b/gists.org
index 81126a8..f790533 100644
--- a/gists.org
+++ b/gists.org
@@ -674,6 +674,33 @@ Based on an answer at the [[https://emacs.stackexchange.com/a/77480/34645][Emacs
   - else: Non-nil means case sensitive search.
 #+end_src
 
+* Restrict symbol / command completion to a major mode :emacs:
+
+#+begin_src elisp :tangle gists/restrict-command-to-major-mode.el
+  (defun my/buffer-has-major-mode-p (major-mode _sym buffer)
+    "Return t if BUFFER has MAJOR-MODE set."
+    (eq (buffer-local-value 'major-mode buffer) major-mode))
+
+  (defun my/restrict-symbol (mode symbols)
+    "Restrict SYMBOLS to a certain major MODE.
+
+  Ideally, packages should restrict their own `interactive'
+  commands to their own mode (see the `interactive' help). However,
+  this is not common practice so this little facility makes it
+  easier to restrict symbols to a certain mode. Meaning, the
+  command will not appear in the M-x menu as a possible completion.
+
+  This may be handy if a command may be destructive for a major
+  mode it wasn't meant for.
+
+  Example:
+
+      (my/restrict-symbol 'ledger-mode '(ledger-occur))"
+    (dolist (sym symbols)
+      (put sym 'completion-predicate
+           (apply-partially #'my/buffer-has-major-mode-p mode))))
+#+end_src
+
 * Meta
 ** License
 
diff --git a/gists/restrict-command-to-major-mode.el b/gists/restrict-command-to-major-mode.el
new file mode 100644
index 0000000..da69a73
--- /dev/null
+++ b/gists/restrict-command-to-major-mode.el
@@ -0,0 +1,22 @@
+(defun my/buffer-has-major-mode-p (major-mode _sym buffer)
+  "Return t if BUFFER has MAJOR-MODE set."
+  (eq (buffer-local-value 'major-mode buffer) major-mode))
+
+(defun my/restrict-symbol (mode symbols)
+  "Restrict SYMBOLS to a certain major MODE.
+
+Ideally, packages should restrict their own `interactive'
+commands to their own mode (see the `interactive' help). However,
+this is not common practice so this little facility makes it
+easier to restrict symbols to a certain mode. Meaning, the
+command will not appear in the M-x menu as a possible completion.
+
+This may be handy if a command may be destructive for a major
+mode it wasn't meant for.
+
+Example:
+
+    (my/restrict-symbol 'ledger-mode '(ledger-occur))"
+  (dolist (sym symbols)
+    (put sym 'completion-predicate
+         (apply-partially #'my/buffer-has-major-mode-p mode))))