Issue #19884: readline: Disable the meta modifier key if stdout is not a

terminal to not write the ANSI sequence "\033[1034h" into stdout. This sequence
is used on some terminal (ex: TERM=xterm-256color") to enable support of 8 bit
characters.

Lib/test/test_readline.py

@@ -1,17 +1,20 @@
 """
 Very minimal unittests for parts of the readline module.
-
-These tests were added to check that the libedit emulation on OSX and
-the "real" readline have the same interface for history manipulation. That's
-why the tests cover only a small subset of the interface.
 """
+import os
 import unittest
 from test.support import run_unittest, import_module
+from test.script_helper import assert_python_ok
 
 # Skip tests if there is no readline module
 readline = import_module('readline')
 
 class TestHistoryManipulation (unittest.TestCase):
+    """
+    These tests were added to check that the libedit emulation on OSX and the
+    "real" readline have the same interface for history manipulation. That's
+    why the tests cover only a small subset of the interface.
+    """
 
     @unittest.skipIf(not hasattr(readline, 'clear_history'),
                      "The history update test cannot be run because the "
@@ -40,8 +43,18 @@ class TestHistoryManipulation (unittest.TestCase):
         self.assertEqual(readline.get_current_history_length(), 1)
 
 
+class TestReadline(unittest.TestCase):
+    def test_init(self):
+        # Issue #19884: Ensure that the ANSI sequence "\033[1034h" is not
+        # written into stdout when the readline module is imported and stdout
+        # is redirected to a pipe.
+        rc, stdout, stderr = assert_python_ok('-c', 'import readline',
+                                              TERM='xterm-256color')
+        self.assertEqual(stdout, b'')
+
+
 def test_main():
-    run_unittest(TestHistoryManipulation)
+    run_unittest(TestHistoryManipulation, TestReadline)
 
 if __name__ == "__main__":
     test_main()

Misc/NEWS

@@ -27,6 +27,11 @@ Core and Builtins
 Library
 -------
 
+- Issue #19884: readline: Disable the meta modifier key if stdout is not
+  a terminal to not write the ANSI sequence "\033[1034h" into stdout. This
+  sequence is used on some terminal (ex: TERM=xterm-256color") to enable
+  support of 8 bit characters.
+
 - Issue #21888: plistlib's load() and loads() now work if the fmt parameter is
   specified.
 

Modules/readline.c

@@ -1019,6 +1019,17 @@ setup_readline(readlinestate *mod_state)
 
     mod_state->begidx = PyLong_FromLong(0L);
     mod_state->endidx = PyLong_FromLong(0L);
+
+    if (!isatty(STDOUT_FILENO)) {
+        /* Issue #19884: stdout is no a terminal. Disable meta modifier
+           keys to not write the ANSI sequence "\033[1034h" into stdout. On
+           terminals supporting 8 bit characters like TERM=xterm-256color
+           (which is now the default Fedora since Fedora 18), the meta key is
+           used to enable support of 8 bit characters (ANSI sequence
+           "\033[1034h"). */
+        rl_variable_bind ("enable-meta-key", "off");
+    }
+
     /* Initialize (allows .inputrc to override)
      *
      * XXX: A bug in the readline-2.2 library causes a memory leak