Started addressing my PR comments

Author: tleonhardt

cmd2/cmd2.py

@@ -303,21 +303,6 @@ class EmptyStatement(Exception):
 DisabledCommand = namedtuple('DisabledCommand', ['command_function', 'help_function'])
 
 
-class RedirectionSavedState(object):
-    # Created by each command to store information about their redirection
-    def __init__(self):
-        # Tells if the command is redirecting
-        self.redirecting = False
-
-        # If the command created a process to pipe to, then then is its reader
-        self.pipe_proc_reader = None
-
-        # Used to restore values after the command ends
-        self.saved_self_stdout = None
-        self.saved_sys_stdout = None
-        self.saved_pipe_proc_reader = None
-
-
 class Cmd(cmd.Cmd):
     """An easy but powerful framework for writing line-oriented command interpreters.
 
@@ -433,12 +418,11 @@ def __init__(self, completekey: str = 'tab', stdin=None, stdout=None, persistent
         # Used load command to store the current script dir as a LIFO queue to support _relative_load command
         self._script_dir = []
 
-        # A flag used to protect critical sections in the main thread from stopping due to a KeyboardInterrupt
+        # Context manager used to protect critical sections in the main thread from stopping due to a KeyboardInterrupt
         self.sigint_protection = utils.ContextFlag()
 
         # If the current command created a process to pipe to, then this will be a ProcReader object.
-        # Otherwise the value will be None. This member is used to know when a pipe process can be killed
-        # and also waited upon.
+        # Otherwise it will be None. Its used to know when a pipe process can be killed and/or waited upon.
         self.cur_pipe_proc_reader = None
 
         # Used by complete() for readline tab completion
@@ -1724,7 +1708,7 @@ def onecmd_plus_hooks(self, line: str) -> bool:
             # Keep track of whether or not we were already redirecting before this command
             already_redirecting = self.redirecting
 
-            # This will be a RedirectionSavedState object for the command
+            # This will be a utils.RedirectionSavedState object for the command
             saved_state = None
 
             try:
@@ -1900,22 +1884,19 @@ def _complete_statement(self, line: str) -> Statement:
             raise EmptyStatement()
         return statement
 
-    def _redirect_output(self, statement: Statement) -> Tuple[bool, RedirectionSavedState]:
+    def _redirect_output(self, statement: Statement) -> Tuple[bool, utils.RedirectionSavedState]:
         """Handles output redirection for >, >>, and |.
 
         :param statement: a parsed statement from the user
-        :return: A bool telling if an error occurred and a RedirectionSavedState object
+        :return: A bool telling if an error occurred and a utils.RedirectionSavedState object
         """
         import io
         import subprocess
 
         redir_error = False
 
         # Initialize the saved state
-        saved_state = RedirectionSavedState()
-        saved_state.saved_self_stdout = self.stdout
-        saved_state.saved_sys_stdout = sys.stdout
-        saved_state.saved_pipe_proc_reader = self.cur_pipe_proc_reader
+        saved_state = utils.RedirectionSavedState(self.stdout, sys.stdout, self.cur_pipe_proc_reader)
 
         if not self.allow_redirection:
             return redir_error, saved_state
@@ -1990,7 +1971,7 @@ def _redirect_output(self, statement: Statement) -> Tuple[bool, RedirectionSaved
 
         return redir_error, saved_state
 
-    def _restore_output(self, statement: Statement, saved_state: RedirectionSavedState) -> None:
+    def _restore_output(self, statement: Statement, saved_state: utils.RedirectionSavedState) -> None:
         """Handles restoring state after output redirection as well as
         the actual pipe operation if present.
 

cmd2/utils.py

@@ -342,12 +342,14 @@ def readbytes(self) -> bytes:
 
     def clear(self) -> None:
         """Clear the internal contents"""
-        self.buffer.byte_buf = b''
+        self.buffer.byte_buf = bytearray()
 
-    @staticmethod
-    def isatty() -> bool:
-        """StdSim will never be considered an interactive stream"""
-        return False
+    def isatty(self) -> bool:
+        """StdSim only be considered an interactive stream if `echo` is True and `inner_stream` is a tty."""
+        if self.echo:
+            return self.inner_stream.isatty()
+        else:
+            return False
 
     def __getattr__(self, item: str):
         if item in self.__dict__:
@@ -469,24 +471,43 @@ def _write_bytes(stream: Union[StdSim, BinaryIO, TextIO], to_write: bytes) -> No
 
 
 class ContextFlag(object):
-    """
-    A flag value that is used in a with statement.
+    """A context manager which is also used as a boolean flag value within the default sigint handler.
+
     Its main use is as a flag to prevent the SIGINT handler in cmd2 from raising a KeyboardInterrupt
     while a critical code section has set the flag to True. Because signal handling is always done on the
     main thread, this class is not thread-safe since there is no need.
     """
-    def __init__(self):
+    def __init__(self) -> None:
         # When this flag has a positive value, it is considered set.
         # When it is 0, it is not set. It should never go below 0.
         self.__count = 0
 
-    def __bool__(self):
+    def __bool__(self) -> bool:
         return self.__count > 0
 
-    def __enter__(self):
+    def __enter__(self) -> None:
         self.__count += 1
 
-    def __exit__(self, *args):
+    def __exit__(self, *args) -> None:
         self.__count -= 1
         if self.__count < 0:
             raise ValueError("count has gone below 0")
+
+
+class RedirectionSavedState(object):
+    """Created by each command to store information about their redirection."""
+
+    def __init__(self, self_stdout: Union[StdSim, BinaryIO, TextIO], sys_stdout: Union[StdSim, BinaryIO, TextIO],
+                 pipe_proc_reader: Optional[ProcReader]) -> None:
+        # Used to restore values after the command ends
+        self.saved_self_stdout = self_stdout
+        self.saved_sys_stdout = sys_stdout
+        self.saved_pipe_proc_reader = pipe_proc_reader
+
+        # Tells if the command is redirecting
+        self.redirecting = False
+
+        # If the command created a process to pipe to, then then is its reader
+        self.pipe_proc_reader = None
+
+