bug#30775: 27.0.50; term.el regression handling zsh prompt - extra "%"

[Noam Postavsky]

tags 30775 + patch
quit

> Patch to follow.

>From 8b6f574ec8959891f388ca77abed908e7637a881 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Sun, 11 Mar 2018 20:47:12 -0400
Subject: [PATCH v1] Fix line-wrapping for term.el (Bug#30775)

* lisp/term.el (term-emulate-terminal): Leave line-wrapping state if
point was moved after we entered it.
* test/lisp/term-tests.el (term-line-wrapping-then-motion): New test.
---
 lisp/term.el            | 11 ++++++++---
 test/lisp/term-tests.el | 12 ++++++++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/lisp/term.el b/lisp/term.el
index cf7699abc9..a458cc4fe4 100644
--- a/lisp/term.el
+++ b/lisp/term.el
@@ -2891,9 +2891,11 @@ term-emulate-terminal
                 ;; If the last char was written in last column,
                 ;; back up one column, but remember we did so.
                 ;; Thus we emulate xterm/vt100-style line-wrapping.
-                (cond ((eq (term-current-column) term-width)
-                       (term-move-columns -1)
-                       (setq term-do-line-wrapping t)))
+                (when (eq (term-current-column) term-width)
+                  (term-move-columns -1)
+                  ;; We check after ctrl sequence handling if point
+                  ;; was moved (and leave line-wrapping state if so).
+                  (setq term-do-line-wrapping (point)))
                 (setq term-current-column nil)
                 (setq i funny))
               (pcase-exhaustive (and (<= ctl-end str-length) (aref str i))
@@ -2993,6 +2995,9 @@ term-emulate-terminal
                      (substring str i ctl-end)))))
                 ;; Ignore NUL, Shift Out, Shift In.
                 ((or ?\0 #xE #xF 'nil) nil))
+              ;; Leave line-wrapping state if point was moved.
+              (unless (eq term-do-line-wrapping (point))
+                (setq term-do-line-wrapping nil))
               (if (term-handling-pager)
                   (progn
                     ;; Finish stuff to get ready to handle PAGER.
diff --git a/test/lisp/term-tests.el b/test/lisp/term-tests.el
index 234dfa1f0d..8aaa61a210 100644
--- a/test/lisp/term-tests.el
+++ b/test/lisp/term-tests.el
@@ -124,6 +124,18 @@ term-test-screen-from-input
                     40 12 (list "\eAnSiTc /f" "oo/\n") 'default-directory)
                    "/foo/"))))
 
+(ert-deftest term-line-wrapping-then-motion ()
+  "Make sure we reset the line-wrapping state after moving cursor.
+A real-life example is the default zsh prompt which writes spaces
+to the end of line (triggering line-wrapping state), and then
+sends a carriage return followed by another space to overwrite
+the first character of the line."
+  (let* ((width 10)
+         (strs (list "x" (make-string (1- width) ?_)
+                     "\r_")))
+    (should (equal (term-test-screen-from-input width 12 strs)
+                   (make-string width ?_)))))
+
 (provide 'term-tests)
 
 ;;; term-tests.el ends here
-- 
2.11.0