Merge pull request #396 from python-cmd2/readline_warning_py2

Readline warning py2

Author: tleonhardt

cmd2.py

@@ -155,15 +155,21 @@ class RlType(Enum):
     orig_pyreadline_display = readline.rl.mode._display_completions
 
 elif 'gnureadline' in sys.modules or 'readline' in sys.modules:
-    rl_type = RlType.GNU
+    # We don't support libedit
+    if 'libedit' not in readline.__doc__:
+        rl_type = RlType.GNU
 
-    # We need wcswidth to calculate display width of tab completions
-    from wcwidth import wcswidth
+        # We need wcswidth to calculate display width of tab completions
+        from wcwidth import wcswidth
 
-    # Load the readline lib so we can make changes to it
-    import ctypes
-    readline_lib = ctypes.CDLL(readline.__file__)
+        # Load the readline lib so we can make changes to it
+        import ctypes
+        readline_lib = ctypes.CDLL(readline.__file__)
 
+if rl_type == RlType.NONE:
+    rl_err_msg = "Tab completion has been disabled since no supported version of readline was found\n"
+    rl_err_msg += "To resolve this, install pyreadline on Windows or gnureadline on Mac\n"
+    sys.stderr.write(rl_err_msg)
 
 # BrokenPipeError and FileNotFoundError exist only in Python 3. Use IOError for Python 2.
 if six.PY3:
@@ -690,6 +696,9 @@ def strip_ansi(text):
 def _pop_readline_history(clear_history=True):
     """Returns a copy of readline's history and optionally clears it (default)"""
     # noinspection PyArgumentList
+    if rl_type == RlType.NONE:
+        return []
+
     history = [
         readline.get_history_item(i)
         for i in range(1, 1 + readline.get_current_history_length())
@@ -701,10 +710,11 @@ def _pop_readline_history(clear_history=True):
 
 def _push_readline_history(history, clear_history=True):
     """Restores readline's history and optionally clears it first (default)"""
-    if clear_history:
-        readline.clear_history()
-    for line in history:
-        readline.add_history(line)
+    if rl_type != RlType.NONE:
+        if clear_history:
+            readline.clear_history()
+        for line in history:
+            readline.add_history(line)
 
 
 def _complete_from_cmd(cmd_obj, text, line, begidx, endidx):
@@ -838,7 +848,7 @@ def enter_submenu(parent_cmd, line):
             original_attributes = self._get_original_attributes()
             history = _pop_readline_history()
 
-            if self.persistent_history_file:
+            if self.persistent_history_file and rl_type != RlType.NONE:
                 try:
                     readline.read_history_file(self.persistent_history_file)
                 except FILE_NOT_FOUND_ERROR:
@@ -871,7 +881,7 @@ def enter_submenu(parent_cmd, line):
                 self._copy_out_shared_attrs(parent_cmd, original_attributes)
 
                 # write submenu history
-                if self.persistent_history_file:
+                if self.persistent_history_file and rl_type != RlType.NONE:
                     readline.write_history_file(self.persistent_history_file)
                 # reset main app history before exit
                 _push_readline_history(history)
@@ -1030,7 +1040,7 @@ def __init__(self, completekey='tab', stdin=None, stdout=None, persistent_histor
                 pass
 
         # If persistent readline history is enabled, then read history from file and register to write to file at exit
-        if persistent_history_file:
+        if persistent_history_file and rl_type != RlType.NONE:
             persistent_history_file = os.path.expanduser(persistent_history_file)
             try:
                 readline.read_history_file(persistent_history_file)
@@ -1972,7 +1982,7 @@ def complete(self, text, state):
         :param text: str - the current word that user is typing
         :param state: int - non-negative integer
         """
-        if state == 0:
+        if state == 0 and rl_type != RlType.NONE:
             unclosed_quote = ''
             self.set_completion_defaults()
 
@@ -3061,9 +3071,12 @@ def select(self, opts, prompt='Your choice? '):
             self.poutput('  %2d. %s\n' % (idx + 1, text))
         while True:
             response = sm.input(prompt)
-            hlen = readline.get_current_history_length()
-            if hlen >= 1 and response != '':
-                readline.remove_history_item(hlen - 1)
+
+            if rl_type != RlType.NONE:
+                hlen = readline.get_current_history_length()
+                if hlen >= 1 and response != '':
+                    readline.remove_history_item(hlen - 1)
+
             try:
                 response = int(response)
                 result = fulloptions[response - 1][0]