From b16f9bbd223f92b5a928a28d7bbf9b6dd925d9e3 Mon Sep 17 00:00:00 2001
From: Maciej Szlosarczyk <maciej@sosek.net>
Date: Thu, 11 Jul 2019 23:20:16 +0300
Subject: [PATCH] Automatically run ctags command on save

---
 08ctags.el  | 41 ++++++++++++++++++++++++++++++-----------
 20clang.el  |  2 +-
 20erlang.el |  7 +++++--
 20ruby.el   |  8 ++++++--
 4 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/08ctags.el b/08ctags.el
index 8535c9a..3b7407a 100644
--- a/08ctags.el
+++ b/08ctags.el
@@ -1,9 +1,14 @@
 ;; Do not mix ctags between folders
+(provide 'my-ctags-config)
+
 (setq tags-add-tables nil)
+(setq ctags/refresh-command
+      (format "ctags -e -R -f %sTAGS %s."
+              default-directory default-directory))
 
 ;; Sentinel function for capturing ctags
-(defun ctags-process-callback (process event)
-  "Show status of asynchronous ctags-process after it finishes."
+(defun ctags/process-callback (process event)
+  "Show status of asynchronous ctags/process after it finishes."
   (cond
    ((string-equal event "finished\n")
     (message "Creating tag files...completed")
@@ -14,17 +19,31 @@
     (pop-to-buffer (get-buffer "*ctags*"))
     )))
 
-(setq ctags-refresh-command
-      (format "ctags -e -R -f %sTAGS %s."
-              default-directory default-directory))
-
-(defun refresh-ctags ()
+(cl-defun ctags/refresh-ctags (&key silent)
   "Refresh ctags according to currently set command."
   (interactive)
 
-  (message "Starting ctags process")
-  (start-process-shell-command "ctags" "*ctags*" ctags-refresh-command)
-  (set-process-sentinel (get-process "ctags") 'ctags-process-callback))
+  ;; Print message if not silent
+  (when (not silent) (message "Starting ctags process..."))
+
+  ;; Return if a version of the process is already running
+  (when (not (get-process "ctags"))
+    (start-process-shell-command "ctags" "*ctags*" ctags/refresh-command)
+    (set-process-sentinel (get-process "ctags") 'ctags/process-callback)))
 
 ;; Ctags bindings
-(define-key prog-mode-map (kbd "C-c E") 'refresh-ctags)
+(define-key prog-mode-map (kbd "C-c E") 'ctags/refresh-ctags)
+
+;; Automatically update tags on save, but be silent about it.
+(setq ctags/major-modes-to-update-on-save '())
+(defun ctags/update-tags-on-save ()
+  "Update tags if current major mode is part of the list."
+  (interactive)
+  (when (member major-mode ctags/major-modes-to-update-on-save)
+    (ctags/refresh-ctags :silent t)))
+
+(defun ctags/update-this-mode-on-save (mode)
+  "Update MODE on save."
+  (add-to-list (make-local-variable 'ctags/major-modes-to-update-on-save) mode))
+
+(add-hook 'after-save-hook 'ctags/update-tags-on-save)
diff --git a/20clang.el b/20clang.el
index 9c0a972..2ab385f 100644
--- a/20clang.el
+++ b/20clang.el
@@ -7,7 +7,7 @@
                '(company-etags company-yasnippet))
 
   (setq-local
-   ctags-refresh-command
+   ctags/refresh-command
    (format
     "ctags -e -R --languages=C -f %sTAGS %s."
     (projectile-project-root) (projectile-project-root)
diff --git a/20erlang.el b/20erlang.el
index c8c2ac2..a5cb68e 100644
--- a/20erlang.el
+++ b/20erlang.el
@@ -27,7 +27,7 @@
 
   ;; Set specific ctags command
   (setq-local
-   ctags-refresh-command
+   ctags/refresh-command
    (format
     "ctags -e -R --languages=erlang -f %sTAGS %s. %slib/stdlib-* %slib/kernel-*"
     (projectile-project-root) (projectile-project-root)
@@ -44,4 +44,7 @@
 
   (activate-erlang-mode)
   ;; Enable flycheck
-  (flycheck-select-checker 'erlang-otp))
+  (flycheck-select-checker 'erlang-otp)
+
+    ;; Automatically update tags on save
+  (ctags/update-this-mode-on-save 'erlang-mode))
diff --git a/20ruby.el b/20ruby.el
index 1f2f402..7da8e77 100644
--- a/20ruby.el
+++ b/20ruby.el
@@ -26,10 +26,14 @@
   (setq ruby-insert-encoding-magic-comment nil)
 
   ;; Company list override
-  (add-to-list (make-local-variable 'company-backends) '(company-etags company-yasnippet))
+  (add-to-list (make-local-variable 'company-backends)
+               '(company-etags company-yasnippet))
+
+  ;; Automatically update tags on save
+  (ctags/update-this-mode-on-save 'enh-ruby-mode)
 
   ;; Set specific ctags command
-  (setq-local ctags-refresh-command
+  (setq-local ctags/refresh-command
               (format "ctags -e -R --languages=ruby -f %sTAGS %s. $(bundle list --paths)"
                       (projectile-project-root) (projectile-project-root))))