bug#18133: Suppressing asynchronous command output

[Reuben Thomas <rrt@sc3d.org>]

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On 26 December 2016 at 23:27, Juri Linkov <juri@linkov.net> wrote:

[message cut]

Thanks, Juri, for helping again with this bug.

I attach an updated version of my patch, which uses an :options setting for
display-buffer-alist so that the current behaviour remains the default, and
runs a preoutput-filter-function which calls display-buffer only when
output is added to an empty buffer.

I believe this addresses the performance and behaviour issues, without the
need for another user option.

It is also rather shorter than the previous patch.

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http://rrt.sc3d.org

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From 935d50d93d37d2d4649673a5d52ec4efe4abce7b Mon Sep 17 00:00:00 2001
From: Reuben Thomas <rrt@sc3d.org>
Date: Mon, 19 Dec 2016 15:38:36 +0000
Subject: [PATCH] Delay showing Async Shell Command buffer until output
 (Bug#18133)

* lisp/comint.el (comint-input-filter): Add process argument.
(comint-output-filter-functions): Add `comint-make-buffer-visible' to
the list, document the second argument (the process).
(comint-send-input): Call input and output filter functions with
process argument.
(comint-output-filter): Call output filter functions with process
argument.
(comint-make-buffer-visible): New hook function, to make Async Shell
Command buffer visible.
(comint-postoutput-scroll-to-bottom):
(comint-watch-for-password-prompt): Add dummy process argument.
* lisp/window.el (display-buffer-alist): Add a default entry to hide
Async Shell Command output window.
* lisp/ansi-color.el (ansi-color-process-output): Add a dummy process
argument.
---
 lisp/comint.el | 22 ++++++++++++++++------
 lisp/window.el |  5 ++++-
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/lisp/comint.el b/lisp/comint.el
index b9c65b0..6fa2fc9 100644
--- a/lisp/comint.el
+++ b/lisp/comint.el
@@ -1913,12 +1913,12 @@ comint-send-input
         ;; but that scrolled the buffer in undesirable ways.
         (run-hook-with-args 'comint-output-filter-functions "")))))
 
-(defvar comint-preoutput-filter-functions nil
+(defvar comint-preoutput-filter-functions '(comint-make-newly-written-buffer-visible)
   "List of functions to call before inserting Comint output into the buffer.
-Each function gets one argument, a string containing the text received
-from the subprocess.  It should return the string to insert, perhaps
-the same string that was received, or perhaps a modified or transformed
-string.
+Each function gets two argument, a string containing the text received
+from the subprocess, and the process.  It should return the string to
+insert, perhaps the same string that was received, or perhaps a modified or
+transformed string.
 
 The functions on the list are called sequentially, and each one is
 given the string returned by the previous one.  The string returned by
@@ -2023,7 +2023,7 @@ comint-output-filter
 		(let ((functions
                        (default-value 'comint-preoutput-filter-functions)))
 		  (while (and functions string)
-		    (setq string (funcall (car functions) string))
+		    (setq string (funcall (car functions) string process))
 		    (setq functions (cdr functions))))
 	      (setq string (funcall (car functions) string)))
 	    (setq functions (cdr functions))))
@@ -2111,6 +2111,16 @@ comint-output-filter
 	      (add-text-properties prompt-start (point) '(rear-nonsticky t)))
 	    (goto-char saved-point)))))))
 
+(defun comint-make-newly-written-buffer-visible (string process)
+  "Make the output buffer visible when output is added to an empty buffer.
+Useful in `comint-preoutput-filter-functions'."
+  (let ((buffer (process-buffer process)))
+    (when (and (= 0 (buffer-size buffer))
+               (string-match-p "\\*Async Shell Command\\*"
+                               (buffer-name buffer)))
+      (display-buffer (process-buffer process))))
+  string)
+
 (defun comint-preinput-scroll-to-bottom ()
   "Go to the end of buffer in all windows showing it.
 Movement occurs if point in the selected window is not after the process mark,
diff --git a/lisp/window.el b/lisp/window.el
index fdb67ed..a49f4a3 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -6797,7 +6797,10 @@ display-buffer-alist
 		(choice :tag "Condition"
 			regexp
 			(function :tag "Matcher function"))
-		:value-type ,display-buffer--action-custom-type)
+		:value-type ,display-buffer--action-custom-type
+		:options (("\\*Async Shell Command\\*"
+                           (cons
+                            (const display-buffer-no-window) (const nil)))))
   :risky t
   :version "24.1"
   :group 'windows)
-- 
2.7.4