Initial implementation of modular command loading

Issue #943

New class CommandSet can be used to tag a class as a command class. If
the constructor is simple, the object will automatically be instantiated
and loaded.
New register_command decorator to tag any arbitrary function as a
command.

2 files changed, 186 insertions, 2 deletions

diff --git a/cmd2/cmd2.py b/cmd2/cmd2.py
index 70ec508c..9a98b550 100644
--- a/cmd2/cmd2.py
+++ b/cmd2/cmd2.py
@@ -37,14 +37,17 @@ import pickle
 import re
 import sys
 import threading
+import types
 from code import InteractiveConsole
 from collections import namedtuple
 from contextlib import redirect_stdout
-from typing import Any, Callable, Dict, Iterable, List, Mapping, Optional, Tuple, Type, Union
+from typing import Any, AnyStr, Callable, Dict, Iterable, List, Mapping, Optional, Tuple, Type, Union
 
 from . import ansi, constants, plugin, utils
 from .argparse_custom import DEFAULT_ARGUMENT_PARSER, CompletionItem
 from .clipboard import can_clip, get_paste_buffer, write_to_paste_buffer
+from .command_definition import _UNBOUND_COMMANDS, CommandSet, _PartialPassthru
+from .constants import COMMAND_FUNC_PREFIX, COMPLETER_FUNC_PREFIX, HELP_FUNC_PREFIX
 from .decorators import with_argparser
 from .exceptions import Cmd2ShlexError, EmbeddedConsoleExit, EmptyStatement, RedirectionError, SkipPostcommandHooks
 from .history import History, HistoryItem
@@ -130,7 +133,8 @@ class Cmd(cmd.Cmd):
                  startup_script: str = '', use_ipython: bool = False,
                  allow_cli_args: bool = True, transcript_files: Optional[List[str]] = None,
                  allow_redirection: bool = True, multiline_commands: Optional[List[str]] = None,
-                 terminators: Optional[List[str]] = None, shortcuts: Optional[Dict[str, str]] = None) -> None:
+                 terminators: Optional[List[str]] = None, shortcuts: Optional[Dict[str, str]] = None,
+                 command_sets: Optional[Iterable[CommandSet]] = None) -> None:
         """An easy but powerful framework for writing line-oriented command
         interpreters. Extends Python's cmd package.
 
@@ -381,6 +385,64 @@ class Cmd(cmd.Cmd):
         # If False, then complete() will sort the matches using self.default_sort_key before they are displayed.
         self.matches_sorted = False
 
+        # Load modular commands
+        self._command_sets = command_sets if command_sets is not None else []
+        self._load_modular_commands()
+
+    def _load_modular_commands(self) -> None:
+        """
+        Load modular command definitions.
+        :return: None
+        """
+
+        # start by loading registered functions as commands
+        for cmd_name, cmd_func, cmd_completer, cmd_help in _UNBOUND_COMMANDS:
+            assert getattr(self, cmd_func.__name__, None) is None, 'Duplicate command function registered: ' + cmd_name
+            setattr(self, cmd_func.__name__, types.MethodType(cmd_func, self))
+            if cmd_completer is not None:
+                assert getattr(self, cmd_completer.__name__, None) is None, \
+                    'Duplicate command completer registered: ' + cmd_completer.__name__
+                setattr(self, cmd_completer.__name__, types.MethodType(cmd_completer, self))
+            if cmd_help is not None:
+                assert getattr(self, cmd_help.__name__, None) is None, \
+                    'Duplicate command help registered: ' + cmd_help.__name__
+                setattr(self, cmd_help.__name__, types.MethodType(cmd_help, self))
+
+        # Search for all subclasses of CommandSet, instantiate them if they weren't provided in the constructor
+        all_commandset_defs = CommandSet.__subclasses__()
+        existing_commandset_types = [type(command_set) for command_set in self._command_sets]
+        for cmdset_type in all_commandset_defs:
+            init_sig = inspect.signature(cmdset_type.__init__)
+            if cmdset_type in existing_commandset_types or len(init_sig.parameters) != 1 or 'self' not in init_sig.parameters:
+                continue
+            cmdset = cmdset_type()
+            self._command_sets.append(cmdset)
+
+        # initialize each CommandSet and register all matching functions as command, helper, completer functions
+        for cmdset in self._command_sets:
+            cmdset.on_register(self)
+            methods = inspect.getmembers(cmdset, predicate=lambda meth: inspect.ismethod(
+                meth) and meth.__name__.startswith(COMMAND_FUNC_PREFIX))
+
+            for method in methods:
+                assert getattr(self, method[0], None) is None, \
+                    'In {}: Duplicate command function: {}'.format(cmdset_type.__name__, method[0])
+
+                command_wrapper = _PartialPassthru(method[1], self)
+                setattr(self, method[0], command_wrapper)
+
+                command = method[0][len(COMMAND_FUNC_PREFIX):]
+
+                completer_func_name = COMPLETER_FUNC_PREFIX + command
+                cmd_completer = getattr(cmdset, completer_func_name, None)
+                if cmd_completer and not getattr(self, completer_func_name, None):
+                    completer_wrapper = _PartialPassthru(cmd_completer, self)
+                    setattr(self, completer_func_name, completer_wrapper)
+                cmd_help = getattr(cmdset, HELP_FUNC_PREFIX + command, None)
+                if cmd_help and not getattr(self, HELP_FUNC_PREFIX + command, None):
+                    help_wrapper = _PartialPassthru(cmd_help, self)
+                    setattr(self, HELP_FUNC_PREFIX + command, help_wrapper)
+
     def add_settable(self, settable: Settable) -> None:
         """
         Convenience method to add a settable parameter to ``self.settables``
diff --git a/cmd2/command_definition.py b/cmd2/command_definition.py
new file mode 100644
index 00000000..f08040bb
--- /dev/null
+++ b/cmd2/command_definition.py
@@ -0,0 +1,122 @@
+# coding=utf-8
+"""
+Supports the definition of commands in separate classes to be composed into cmd2.Cmd
+"""
+import functools
+from typing import (
+    Callable,
+    Iterable,
+    List,
+    Optional,
+    Tuple,
+    Type,
+    Union,
+)
+from .constants import COMMAND_FUNC_PREFIX, HELP_FUNC_PREFIX, COMPLETER_FUNC_PREFIX
+
+# Allows IDEs to resolve types without impacting imports at runtime, breaking circular dependency issues
+try:
+    from typing import TYPE_CHECKING
+    if TYPE_CHECKING:
+        from .cmd2 import Cmd, Statement
+        import argparse
+except ImportError:
+    pass
+
+_UNBOUND_COMMANDS = []  # type: List[Tuple[str, Callable, Optional[Callable], Optional[Callable]]]
+"""
+Registered command tuples. (command, do_ function, complete_ function, help_ function
+"""
+
+
+class _PartialPassthru(functools.partial):
+    """
+    Wrapper around partial function that passes through getattr, setattr, and dir to the wrapped function.
+    This allows for CommandSet functions to be wrapped while maintaining the decorated properties
+    """
+    def __getattr__(self, item):
+        return getattr(self.func, item)
+
+    def __setattr__(self, key, value):
+        return setattr(self.func, key, value)
+
+    def __dir__(self) -> Iterable[str]:
+        return dir(self.func)
+
+
+def register_command(cmd_func: Callable[['Cmd', Union['Statement', 'argparse.Namespace']], None]):
+    """
+    Decorator that allows an arbitrary function to be automatically registered as a command.
+    If there is a help_ or complete_ function that matches this command, that will also be registered.
+
+    :param cmd_func: Function to register as a cmd2 command
+    :return:
+    """
+    assert cmd_func.__name__.startswith(COMMAND_FUNC_PREFIX), 'Command functions must start with `do_`'
+
+    import inspect
+
+    cmd_name = cmd_func.__name__[len(COMMAND_FUNC_PREFIX):]
+    cmd_completer = None
+    cmd_help = None
+
+    module = inspect.getmodule(cmd_func)
+
+    module_funcs = [mf for mf in inspect.getmembers(module) if inspect.isfunction(mf[1])]
+    for mf in module_funcs:
+        if mf[0] == COMPLETER_FUNC_PREFIX + cmd_name:
+            cmd_completer = mf[1]
+        elif mf[0] == HELP_FUNC_PREFIX + cmd_name:
+            cmd_help = mf[1]
+        if cmd_completer is not None and cmd_help is not None:
+            break
+
+    _UNBOUND_COMMANDS.append((cmd_name, cmd_func, cmd_completer, cmd_help))
+
+
+def with_default_category(category: str):
+    """
+    Decorator that applies a category to all ``do_*`` command methods in a class that do not already
+    have a category specified.
+
+    :param category: category to put all uncategorized commands in
+    :return: decorator function
+    """
+
+    def decorate_class(cls: Type[CommandSet]):
+        from .constants import CMD_ATTR_HELP_CATEGORY
+        import inspect
+        from .decorators import with_category
+        methods = inspect.getmembers(
+            cls,
+            predicate=lambda meth: inspect.isfunction(meth) and meth.__name__.startswith(COMMAND_FUNC_PREFIX))
+        category_decorator = with_category(category)
+        for method in methods:
+            if not hasattr(method[1], CMD_ATTR_HELP_CATEGORY):
+                setattr(cls, method[0], category_decorator(method[1]))
+        return cls
+    return decorate_class
+
+
+class CommandSet(object):
+    """
+    Base class for defining sets of commands to load in cmd2.
+
+    ``with_default_category`` can be used to apply a default category to all commands in the CommandSet.
+
+    ``do_``, ``help_``, and ``complete_`` functions differ only in that they're now required to accept
+    a reference to ``cmd2.Cmd`` as the first argument after self.
+    """
+
+    def __init__(self):
+        self._cmd = None  # type: Optional[Cmd]
+
+    def on_register(self, cmd: 'Cmd'):
+        """
+        Called by cmd2.Cmd when a CommandSet is registered. Subclasses can override this
+        to perform an initialization requiring access to the Cmd object.
+
+        :param cmd: The cmd2 main application
+        :return: None
+        """
+        self._cmd = cmd