bug#20084: comint-highlight-prompt overrides ANSI colors in 24.4

[Wolfgang Jenkner <wjenkner@inode.at>]

On Wed, Mar 11 2015, Glenn Morris wrote:

> Perhaps related to http://debbugs.gnu.org/14744, which I see was applied
> 2013-08-08, without any comment being made to the associated bug report, sigh.

Another symptom of the same bug introduced there is that copious
colourful output, as produced by, say, `ls /usr/bin', will have "white
spots".

I've been using something like the following patch for some time:

-- >8 --
Subject: [PATCH] Preserve face text properties in comint prompt.

* lisp/comint.el (comint-snapshot-last-prompt): Use
font-lock-prepend-text-property for comint-highlight-prompt.
(comint-output-filter): Remove only comint-highlight-prompt.

Thus, the original face text property of a prompt "candidate" (the
last line of an output chunk not ending with a newline) is
preserved.  This amends the fixing of bug#14744.  (Bug#20084)
---
 lisp/comint.el | 38 ++++++++++++++++++++++++++++++--------
 1 file changed, 30 insertions(+), 8 deletions(-)

diff --git a/lisp/comint.el b/lisp/comint.el
index b52d7fd..65b9c3c 100644
--- a/lisp/comint.el
+++ b/lisp/comint.el
@@ -1926,10 +1926,10 @@ the start, the cdr to the end of the last prompt recognized.")
 Freezes the `font-lock-face' text property in place."
   (when comint-last-prompt
     (with-silent-modifications
-      (add-text-properties
+      (font-lock-prepend-text-property
        (car comint-last-prompt)
        (cdr comint-last-prompt)
-       '(font-lock-face comint-highlight-prompt)))
+       'font-lock-face 'comint-highlight-prompt))
     ;; Reset comint-last-prompt so later on comint-output-filter does
     ;; not remove the font-lock-face text property of the previous
     ;; (this) prompt.
@@ -2081,14 +2081,36 @@ Make backspaces delete the previous character."
 		  (add-text-properties prompt-start (point)
 				       '(read-only t front-sticky (read-only)))))
 	      (when comint-last-prompt
-		(remove-text-properties (car comint-last-prompt)
-					(cdr comint-last-prompt)
-					'(font-lock-face)))
+		(let ((start (car comint-last-prompt))
+		      (limit (cdr comint-last-prompt))
+		      face end)
+		  (with-silent-modifications
+		    (while
+			(progn
+			  (setq end
+				(next-single-property-change start
+							     'font-lock-face
+							     nil
+							     limit))
+			  (setq face (get-text-property start 'font-lock-face))
+			  (put-text-property
+			   start end 'font-lock-face
+			   (if (and (consp face)
+				    (not (or
+					  (eq (car face) 'foreground-color)
+					  (eq (car face) 'background-color)
+					  (keywordp (car face)))))
+			       (remove 'comint-highlight-prompt face)
+			     (unless (eq face 'comint-highlight-prompt)
+			       face)))
+			  (< (setq start end) limit))))))
 	      (setq comint-last-prompt
 		    (cons (copy-marker prompt-start) (point-marker)))
-	      (add-text-properties prompt-start (point)
-				   '(rear-nonsticky t
-				     font-lock-face comint-highlight-prompt)))
+	      (with-silent-modifications
+		(font-lock-prepend-text-property prompt-start (point)
+						 'font-lock-face
+						 'comint-highlight-prompt)
+		(add-text-properties prompt-start (point) '(rear-nonsticky t))))
 	    (goto-char saved-point)))))))
 
 (defun comint-preinput-scroll-to-bottom ()
-- 
2.3.0