bug#19650:

[Carlos Pita <carlosjosepita@gmail.com>]

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I've been doing my homework:

1) Changing insert for insert-before-markers is problematic because it
somehow wreaks havoc with font locking. I guess some other markers are
being moved around besides he-string-end, maybe the one pointing to
the end of the prompt or something like that (since everything gets
colored the same the prompt is). Moreover, the he-string-beg marker
would still point to the wrong place no matter what its type were.

2) This will work for the end marker: (set-marker-insertion-type
he-string-end t), but it's too invasive regarding hippie-expand. Also,
it assumes the user is indeed using hippie-expand. But maybe changing
the insertion type of he-string-end just around the
delete-region/insert and just in case hippie-expand is currently
provided will do the dirty job. Again, this doesn't fix the
he-string-beg marker at all.

3) Same as (2) above, but saving/restoring the *positions*  of both
he-string-beg and he-string-end. This is the best solution I could
figure out till now. Take a look at the attached patch, please.

What do you think?

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--- py1.el	2015-01-22 13:34:02.863974265 -0300
+++ py2.el	2015-01-22 13:34:18.143826873 -0300
@@ -16,21 +16,28 @@
             (buffer-undo-list t))
         ;; When input hasn't changed, do nothing.
         (when (not (string= input old-input))
-          (delete-region (cdr (python-util-comint-last-prompt)) (point-max))
-          (insert
-           (python-shell-font-lock-with-font-lock-buffer
-             (delete-region (line-beginning-position)
-                            (line-end-position))
-             (insert input)
-             ;; Ensure buffer is fontified, keeping it
-             ;; compatible with Emacs < 24.4.
-             (if (fboundp 'font-lock-ensure)
-                 (funcall 'font-lock-ensure)
-               (font-lock-default-fontify-buffer))
-             ;; Replace FACE text properties with FONT-LOCK-FACE so
-             ;; they are not overwritten by comint buffer's font lock.
-             (python-util-text-properties-replace-name
-              'face 'font-lock-face)
-             (buffer-substring (line-beginning-position)
-                               (line-end-position))))
-          (goto-char current-point))))))
+          (let ((beg) (end))
+            (when (featurep 'hippie-exp)
+              (setq beg (marker-position he-string-beg)
+                    end (marker-position he-string-end)))
+            (delete-region (cdr (python-util-comint-last-prompt)) (point-max))
+            (insert
+             (python-shell-font-lock-with-font-lock-buffer
+               (delete-region (line-beginning-position)
+                              (line-end-position))
+               (insert input)
+               ;; Ensure buffer is fontified, keeping it
+               ;; compatible with Emacs < 24.4.
+               (if (fboundp 'font-lock-ensure)
+                   (funcall 'font-lock-ensure)
+                 (font-lock-default-fontify-buffer))
+               ;; Replace FACE text properties with FONT-LOCK-FACE so
+               ;; they are not overwritten by comint buffer's font lock.
+               (python-util-text-properties-replace-name
+                'face 'font-lock-face)
+               (buffer-substring (line-beginning-position)
+                                 (line-end-position))))
+            (when (featurep 'hippie-exp)
+              (set-marker he-string-beg beg)
+              (set-marker he-string-end end))
+            (goto-char current-point)))))))