From f054c4983f9a90d8bf411f6d06c327a3fa382f4b Mon Sep 17 00:00:00 2001
From: Philip K <philip@warpmail.net>
Date: Mon, 20 Jul 2020 21:20:34 +0200
Subject: [PATCH] Add project-kill-buffer-conditions

This replaces its negation, project-kill-buffers-ignores, from the
previous version.
---
 lisp/progmodes/project.el | 102 +++++++++++++++++++++++++++++++-------
 1 file changed, 83 insertions(+), 19 deletions(-)

diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 67ce3dc7d9..50c164ebc7 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -843,16 +843,52 @@ project-switch-to-buffer
       nil
       predicate))))
 
-(defcustom project-kill-buffers-ignores
-  '("\\*Help\\*")
-  "Conditions for buffers `project-kill-buffers' should not kill.
-Each condition is either a regular expression matching a buffer
-name, or a predicate function that takes a buffer object as
-argument and returns non-nil if it matches.  Buffers that match
-any of the conditions will not be killed."
-  :type '(repeat (choice regexp function))
+(defcustom project-kill-buffer-conditions
+  '(buffer-file-name    ; All file-visiting buffers are included.
+    ;; Most of the temp buffers in the background:
+    (major-mode . fundamental-mode)
+    ;; non-text buffer such as xref, occur, vc, log, ...
+    (and (derived-mode . special-mode)
+         (not (major-mode . help-mode)))
+    (derived-mode . compilation-mode)
+    (derived-mode . dired-mode)
+    (derived-mode . diff-mode))
+  "Conditions for buffers `project-kill-buffers' should kill.
+Each condition is either:
+- a regular expression, to match a buffer name,
+- a predicate function that takes a buffer object as argument
+  and returns non-nil if the buffer should be killed,
+- a symbol, denoting a buffer local variable, where the buffer
+  is killed if it's value is non-nil. If the symbol also has a
+  function slot, it will be interpreted as a function first.
+- a cons-cell, where the car describes how to interpret the cdr.
+  The car can be one of the following:
+  * `major-mode': the buffer is killed if the buffers major
+    mode is eq to the cons-cell's cdr
+  * `defived-mode': the buffer is killed if the buffers major
+    mode is derived from the major mode denoted by the cons-cell's
+    cdr
+  * `not': the cdr is interpreted as a negation of a condition.
+  * `and': the cdr is a list of recursive conditions, that all have
+    to be met.
+  * `or': the cdr is a list of recursive conditions, of which at
+    least one has to be met.
+
+Buffers that match any of the conditions will not be killed."
+  :type '(repeat (choice regexp function symbol
+                         (cons :tag "Major mode"
+                               (const major-mode) symbol)
+                         (cons :tag "Derived mode"
+                               (const derived-mode) symbol)
+                         (cons :tag "Negation"
+                               (const not) sexp)
+                         (cons :tag "Conjunction"
+                               (const and) sexp)
+                         (cons :tag "Disjunction"
+                               (const or) sexp)))
   :version "28.1"
-  :package-version '(project . "0.5.0"))
+  :group 'project
+  :package-version '(project . "0.6.0"))
 
 (defun project--buffer-list (pr)
   "Return the list of all buffers in project PR."
@@ -864,6 +900,38 @@ project--buffer-list
         (push buf bufs)))
     (nreverse bufs)))
 
+(defun project--kill-buffer-check (buf conds)
+  "Return non-nil, if buffer BUF matches any CONDS.
+CONDS is a list of conditions. See
+`project-kill-buffer-conditions' for more details."
+  (catch 'kill
+    (dolist (c conds)
+      (when (cond
+             ((stringp c)
+              (string-match-p c (buffer-name buf)))
+             ((symbolp c)
+              (funcall c buf))
+             ((eq (car-safe c) 'major-mode)
+              (eq (buffer-local-value 'major-mode buf)
+                  (cdr c)))
+             ((eq (car-safe c) 'derived-mode)
+              (provided-mode-derived-p
+               (buffer-local-value 'major-mode buf)
+               (cdr c)))
+             ((eq (car-safe c) 'not)
+              (not (project--kill-buffer-check buf (cdr c))))
+             ((eq (car-safe c) 'and)
+              (seq-every-p
+               (apply-partially #'project--kill-buffer-check
+                                buf)
+               (cdr c)))
+             ((eq (car-safe c) 'or)
+              (seq-some
+               (apply-partially #'project--kill-buffer-check
+                                buf)
+               (cdr c))))
+        (throw 'kill t)))))
+
 ;;;###autoload
 (defun project-kill-buffers ()
   "Kill all live buffers belonging to the current project.
@@ -873,17 +941,13 @@ project-kill-buffers
   (interactive)
   (let ((pr (project-current t)) bufs)
     (dolist (buf (project--buffer-list pr))
-      (unless (seq-some
-               (lambda (c)
-                 (cond ((stringp c)
-                        (string-match-p c (buffer-name buf)))
-                       ((functionp c)
-                        (funcall c buf))))
-               project-kill-buffers-ignores)
+      (when (project--kill-buffer-check buf project-kill-buffer-conditions)
         (push buf bufs)))
-    (when (yes-or-no-p (format "Kill %d buffers in %s? "
-                               (length bufs) (project-root pr)))
-      (mapc #'kill-buffer bufs))))
+    (if (null bufs)
+        (message "No buffers to kill")
+      (when (yes-or-no-p (format "Kill %d buffers in %s? "
+                                 (length bufs) (project-root pr)))
+        (mapc #'kill-buffer bufs)))))
 
 
 ;;; Project list
-- 
2.20.1