Merge branch 'history_improvements' of github.com:python-cmd2/cmd2 into history_improvements

Author: kotfu

CHANGELOG.md

@@ -2,6 +2,7 @@
 * Bug Fixes
     * Fixed bug in how **history** command deals with multiline commands when output to a script
     * Fixed a bug when the ``with_argument_list`` decorator is called with the optional ``preserve_quotes`` argument
+    * Fix bug in ``perror()`` where it would try to print an exception Traceback even if none existed
 * Enhancements
     * Improvements to the **history** command
         * Simplified the display format and made it more similar to **bash**
@@ -10,6 +11,16 @@
         * Added **-v**, **--verbose** flag
             * display history and include expanded commands if they differ from the typed command
     * Added ``matches_sort_key`` to override the default way tab completion matches are sorted
+    * Added ``StdSim.pause_storage`` member which when True will cause ``StdSim`` to not save the output sent to it.
+      See documentation for ``CommandResult`` in ``pyscript_bridge.py`` for reasons pausing the storage can be useful.
+    * Added ability to disable/enable individual commands and entire categories of commands. When a command
+      is disabled, it will not show up in the help menu or tab complete. If a user tries to run the command
+      or call help on it, a command-specific message supplied by the developer will be printed. The following
+      commands were added to support this feature.
+        * ``enable_command()``
+        * ``enable_category()``
+        * ``disable_command()``
+        * ``disable_category()``
 * Potentially breaking changes
     * Made ``cmd2_app`` a positional and required argument of ``AutoCompleter`` since certain functionality now
     requires that it can't be ``None``.

cmd2/cmd2.py

@@ -37,6 +37,7 @@
 import re
 import sys
 import threading
+from collections import namedtuple
 from typing import Any, Callable, Dict, List, Mapping, Optional, Tuple, Type, Union, IO
 
 import colorama
@@ -279,6 +280,10 @@ class EmptyStatement(Exception):
     pass
 
 
+# Contains data about a disabled command which is used to restore its original functions when the command is enabled
+DisabledCommand = namedtuple('DisabledCommand', ['command_function', 'help_function'])
+
+
 class Cmd(cmd.Cmd):
     """An easy but powerful framework for writing line-oriented command interpreters.
 
@@ -521,6 +526,11 @@ def __init__(self, completekey: str = 'tab', stdin=None, stdout=None, persistent
         # being printed by a command.
         self.terminal_lock = threading.RLock()
 
+        # Commands that have been disabled from use. This is to support commands that are only available
+        # during specific states of the application. This dictionary's keys are the command names and its
+        # values are DisabledCommand objects.
+        self.disabled_commands = dict()
+
     # -----  Methods related to presenting output to the user -----
 
     @property
@@ -587,7 +597,7 @@ def perror(self, err: Union[str, Exception], traceback_war: bool = True, err_col
         :param err_color: (optional) color escape to output error with
         :param war_color: (optional) color escape to output warning with
         """
-        if self.debug:
+        if self.debug and sys.exc_info() != (None, None, None):
             import traceback
             traceback.print_exc()
 
@@ -1562,14 +1572,19 @@ def get_all_commands(self) -> List[str]:
                 if name.startswith(COMMAND_FUNC_PREFIX) and callable(getattr(self, name))]
 
     def get_visible_commands(self) -> List[str]:
-        """Returns a list of commands that have not been hidden."""
+        """Returns a list of commands that have not been hidden or disabled."""
         commands = self.get_all_commands()
 
         # Remove the hidden commands
         for name in self.hidden_commands:
             if name in commands:
                 commands.remove(name)
 
+        # Remove the disabled commands
+        for name in self.disabled_commands:
+            if name in commands:
+                commands.remove(name)
+
         return commands
 
     def get_alias_names(self) -> List[str]:
@@ -1953,7 +1968,7 @@ def cmd_func_name(self, command: str) -> str:
     def onecmd(self, statement: Union[Statement, str]) -> bool:
         """ This executes the actual do_* method for a command.
 
-        If the command provided doesn't exist, then it executes _default() instead.
+        If the command provided doesn't exist, then it executes default() instead.
 
         :param statement: intended to be a Statement instance parsed command from the input stream, alternative
                           acceptance of a str is present only for backward compatibility with cmd
@@ -1969,8 +1984,9 @@ def onecmd(self, statement: Union[Statement, str]) -> bool:
         else:
             func = self.cmd_func(statement.command)
             if func:
-                # Since we have a valid command store it in the history
-                if statement.command not in self.exclude_from_history:
+                # Check to see if this command should be stored in history
+                if statement.command not in self.exclude_from_history \
+                        and statement.command not in self.disabled_commands:
                     self.history.append(statement)
 
                 stop = func(statement)
@@ -3186,13 +3202,15 @@ def do_history(self, args: argparse.Namespace) -> None:
 
         # -v must be used alone with no other options
         if args.verbose:
-            if args.clear or args.edit or args.output_file or args.run or args.transcript or args.expanded or args.script:
+            if args.clear or args.edit or args.output_file or args.run or args.transcript \
+                    or args.expanded or args.script:
                 self.poutput("-v can not be used with any other options")
                 self.poutput(self.history_parser.format_usage())
                 return
 
         # -s and -x can only be used if none of these options are present: [-c -r -e -o -t]
-        if (args.script or args.expanded) and (args.clear or args.edit or args.output_file or args.run or args.transcript):
+        if (args.script or args.expanded) \
+                and (args.clear or args.edit or args.output_file or args.run or args.transcript):
             self.poutput("-s and -x can not be used with -c, -r, -e, -o, or -t")
             self.poutput(self.history_parser.format_usage())
             return
@@ -3605,6 +3623,95 @@ def set_window_title(self, title: str) -> None:  # pragma: no cover
         else:
             raise RuntimeError("another thread holds terminal_lock")
 
+    def enable_command(self, command: str) -> None:
+        """
+        Enable a command by restoring its functions
+        :param command: the command being enabled
+        """
+        # If the commands is already enabled, then return
+        if command not in self.disabled_commands:
+            return
+
+        help_func_name = HELP_FUNC_PREFIX + command
+
+        # Restore the command and help functions to their original values
+        dc = self.disabled_commands[command]
+        setattr(self, self.cmd_func_name(command), dc.command_function)
+
+        if dc.help_function is None:
+            delattr(self, help_func_name)
+        else:
+            setattr(self, help_func_name, dc.help_function)
+
+        # Remove the disabled command entry
+        del self.disabled_commands[command]
+
+    def enable_category(self, category: str) -> None:
+        """
+        Enable an entire category of commands
+        :param category: the category to enable
+        """
+        for cmd_name in list(self.disabled_commands):
+            dc = self.disabled_commands[cmd_name]
+            cmd_category = getattr(dc.command_function, HELP_CATEGORY, None)
+            if cmd_category is not None and cmd_category == category:
+                self.enable_command(cmd_name)
+
+    def disable_command(self, command: str, message_to_print: str) -> None:
+        """
+        Disable a command and overwrite its functions
+        :param command: the command being disabled
+        :param message_to_print: what to print when this command is run or help is called on it while disabled
+        """
+        import functools
+
+        # If the commands is already disabled, then return
+        if command in self.disabled_commands:
+            return
+
+        # Make sure this is an actual command
+        command_function = self.cmd_func(command)
+        if command_function is None:
+            raise AttributeError("{} does not refer to a command".format(command))
+
+        help_func_name = HELP_FUNC_PREFIX + command
+
+        # Add the disabled command record
+        self.disabled_commands[command] = DisabledCommand(command_function=command_function,
+                                                          help_function=getattr(self, help_func_name, None))
+
+        # Overwrite the command and help functions to print the message
+        new_func = functools.partial(self._report_disabled_command_usage, message_to_print=message_to_print)
+        setattr(self, self.cmd_func_name(command), new_func)
+        setattr(self, help_func_name, new_func)
+
+    def disable_category(self, category: str, message_to_print: str) -> None:
+        """
+        Disable an entire category of commands
+        :param category: the category to disable
+        :param message_to_print: what to print when anything in this category is run or help is called on it
+                                 while disabled
+        """
+        all_commands = self.get_all_commands()
+
+        for cmd_name in all_commands:
+            func = self.cmd_func(cmd_name)
+            cmd_category = getattr(func, HELP_CATEGORY, None)
+
+            # If this command is in the category, then disable it
+            if cmd_category is not None and cmd_category == category:
+                self.disable_command(cmd_name, message_to_print)
+
+    # noinspection PyUnusedLocal
+    def _report_disabled_command_usage(self, *args, message_to_print: str, **kwargs) -> None:
+        """
+        Report when a disabled command has been run or had help called on it
+        :param args: not used
+        :param message_to_print: the message reporting that the command is disabled
+        :param kwargs: not used
+        """
+        self.poutput(message_to_print)
+
     def cmdloop(self, intro: Optional[str] = None) -> None:
         """This is an outer wrapper around _cmdloop() which deals with extra features provided by cmd2.
 

cmd2/pyscript_bridge.py

@@ -25,9 +25,27 @@ class CommandResult(namedtuple_with_defaults('CommandResult', ['stdout', 'stderr
     Named tuple attributes
     ----------------------
     stdout: str - Output captured from stdout while this command is executing
-    stderr: str - Output captured from stderr while this command is executing. None if no error captured
+    stderr: str - Output captured from stderr while this command is executing. None if no error captured.
     data - Data returned by the command.
 
+    Any combination of these fields can be used when developing a scripting API for a given command.
+    By default stdout and stderr will be captured for you. If there is additional command specific data,
+    then write that to cmd2's _last_result member. That becomes the data member of this tuple.
+
+    In some cases, the data member may contain everything needed for a command and storing stdout
+    and stderr might just be a duplication of data that wastes memory. In that case, the StdSim can
+    be told not to store output with its pause_storage member. While this member is True, any output
+    sent to StdSim won't be saved in its buffer.
+
+    The code would look like this:
+        if isinstance(self.stdout, StdSim):
+            self.stdout.pause_storage = True
+
+        if isinstance(sys.stderr, StdSim):
+            sys.stderr.pause_storage = True
+
+    See StdSim class in utils.py for more information
+
     NOTE: Named tuples are immutable.  So the contents are there for access, not for modification.
     """
     def __bool__(self) -> bool:
@@ -67,25 +85,25 @@ def __call__(self, command: str, echo: Optional[bool] = None) -> CommandResult:
         if echo is None:
             echo = self.cmd_echo
 
-        copy_stdout = StdSim(sys.stdout, echo)
-        copy_stderr = StdSim(sys.stderr, echo)
-
+        # This will be used to capture _cmd2_app.stdout and sys.stdout
         copy_cmd_stdout = StdSim(self._cmd2_app.stdout, echo)
 
+        # This will be used to capture sys.stderr
+        copy_stderr = StdSim(sys.stderr, echo)
+
         self._cmd2_app._last_result = None
 
         try:
             self._cmd2_app.stdout = copy_cmd_stdout
-            with redirect_stdout(copy_stdout):
+            with redirect_stdout(copy_cmd_stdout):
                 with redirect_stderr(copy_stderr):
                     # Include a newline in case it's a multiline command
                     self._cmd2_app.onecmd_plus_hooks(command + '\n')
         finally:
             self._cmd2_app.stdout = copy_cmd_stdout.inner_stream
 
-        # if stderr is empty, set it to None
-        stderr = copy_stderr.getvalue() if copy_stderr.getvalue() else None
-
-        outbuf = copy_cmd_stdout.getvalue() if copy_cmd_stdout.getvalue() else copy_stdout.getvalue()
-        result = CommandResult(stdout=outbuf, stderr=stderr, data=self._cmd2_app._last_result)
+        # Save the output. If stderr is empty, set it to None.
+        result = CommandResult(stdout=copy_cmd_stdout.getvalue(),
+                               stderr=copy_stderr.getvalue() if copy_stderr.getvalue() else None,
+                               data=self._cmd2_app._last_result)
         return result

cmd2/utils.py

@@ -261,28 +261,10 @@ def natural_sort(list_to_sort: Iterable[str]) -> List[str]:
 
 
 class StdSim(object):
-    """Class to simulate behavior of sys.stdout or sys.stderr.
-
+    """
+    Class to simulate behavior of sys.stdout or sys.stderr.
     Stores contents in internal buffer and optionally echos to the inner stream it is simulating.
     """
-    class ByteBuf(object):
-        """Inner class which stores an actual bytes buffer and does the actual output if echo is enabled."""
-        def __init__(self, inner_stream, echo: bool = False,
-                     encoding: str = 'utf-8', errors: str = 'replace') -> None:
-            self.byte_buf = b''
-            self.inner_stream = inner_stream
-            self.echo = echo
-            self.encoding = encoding
-            self.errors = errors
-
-        def write(self, b: bytes) -> None:
-            """Add bytes to internal bytes buffer and if echo is True, echo contents to inner stream."""
-            if not isinstance(b, bytes):
-                raise TypeError('a bytes-like object is required, not {}'.format(type(b)))
-            self.byte_buf += b
-            if self.echo:
-                self.inner_stream.buffer.write(b)
-
     def __init__(self, inner_stream, echo: bool = False,
                  encoding: str = 'utf-8', errors: str = 'replace') -> None:
         """
@@ -292,17 +274,20 @@ def __init__(self, inner_stream, echo: bool = False,
         :param encoding: codec for encoding/decoding strings (defaults to utf-8)
         :param errors: how to handle encoding/decoding errors (defaults to replace)
         """
-        self.buffer = self.ByteBuf(inner_stream, echo)
         self.inner_stream = inner_stream
         self.echo = echo
         self.encoding = encoding
         self.errors = errors
+        self.pause_storage = False
+        self.buffer = ByteBuf(self)
 
     def write(self, s: str) -> None:
         """Add str to internal bytes buffer and if echo is True, echo contents to inner stream"""
         if not isinstance(s, str):
             raise TypeError('write() argument must be str, not {}'.format(type(s)))
-        self.buffer.byte_buf += s.encode(encoding=self.encoding, errors=self.errors)
+
+        if not self.pause_storage:
+            self.buffer.byte_buf += s.encode(encoding=self.encoding, errors=self.errors)
         if self.echo:
             self.inner_stream.write(s)
 
@@ -337,6 +322,24 @@ def __getattr__(self, item: str):
             return getattr(self.inner_stream, item)
 
 
+class ByteBuf(object):
+    """
+    Used by StdSim to write binary data and stores the actual bytes written
+    """
+    def __init__(self, std_sim_instance: StdSim) -> None:
+        self.byte_buf = b''
+        self.std_sim_instance = std_sim_instance
+
+    def write(self, b: bytes) -> None:
+        """Add bytes to internal bytes buffer and if echo is True, echo contents to inner stream."""
+        if not isinstance(b, bytes):
+            raise TypeError('a bytes-like object is required, not {}'.format(type(b)))
+        if not self.std_sim_instance.pause_storage:
+            self.byte_buf += b
+        if self.std_sim_instance.echo:
+            self.std_sim_instance.inner_stream.buffer.write(b)
+
+
 def unquote_redirection_tokens(args: List[str]) -> None:
     """
     Unquote redirection tokens in a list of command-line arguments