Bugfix in emacs key bindings. (Crash when Left/Right was pressed with a negative argument.)

2 files changed, 31 insertions, 1 deletions

diff --git a/prompt_toolkit/document.py b/prompt_toolkit/document.py
index ce34820c..6e7c8564 100644
--- a/prompt_toolkit/document.py
+++ b/prompt_toolkit/document.py
@@ -594,12 +594,18 @@ class Document(object):
         """
         Relative position for cursor left.
         """
+        if count < 0:
+            return self.get_cursor_right_position(-count)
+
         return - min(self.cursor_position_col, count)
 
     def get_cursor_right_position(self, count=1):
         """
         Relative position for cursor_right.
         """
+        if count < 0:
+            return self.get_cursor_left_position(-count)
+
         return min(count, len(self.current_line_after_cursor))
 
     def get_cursor_up_position(self, count=1, preferred_column=None):
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 1072cfa9..c4289385 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -12,8 +12,9 @@ from prompt_toolkit.eventloop.posix import PosixEventLoop
 from prompt_toolkit.history import InMemoryHistory
 from prompt_toolkit.input import PipeInput
 from prompt_toolkit.interface import CommandLineInterface
-from prompt_toolkit.output import DummyOutput
 from prompt_toolkit.key_binding.manager import KeyBindingManager
+from prompt_toolkit.output import DummyOutput
+from prompt_toolkit.terminal.vt100_input import ANSI_SEQUENCES
 from functools import partial
 import pytest
 
@@ -280,6 +281,29 @@ def test_emacs_reverse_search():
     assert result.text == 'line2 second input'
 
 
+def test_emacs_arguments():
+    """
+    Test all Emacs commands with Meta-[0-9] arguments (both positive and
+    negative). No one should crash.
+    """
+    for key in ANSI_SEQUENCES:
+        # Ignore BracketedPaste. This would hang forever, because it waits for
+        # the end sequence.
+        if key != '\x1b[200~':
+            try:
+                # Note: we add an 'X' after the key, because Ctrl-Q (quoted-insert)
+                # expects something to follow. We add an additional \n, because
+                # Ctrl-R and Ctrl-S (reverse-search) expect that.
+                result, cli = _feed_cli_with_input(
+                    'hello\x1b4' + key + 'X\n\n')
+
+                result, cli = _feed_cli_with_input(
+                    'hello\x1b-' + key + 'X\n\n')
+            except KeyboardInterrupt:
+                # This exception should only be raised for Ctrl-C
+                assert key == '\x03'
+
+
 def test_vi_cursor_movements():
     """
     Test cursor movements with Vi key bindings.