1 files changed, 63 insertions, 3 deletions
diff --git a/cmd2/cmd2.py b/cmd2/cmd2.py
index ce19cda8..045e6a1b 100644
--- a/cmd2/cmd2.py
+++ b/cmd2/cmd2.py
@@ -408,6 +408,10 @@ class Cmd(cmd.Cmd):
             import atexit
             atexit.register(readline.write_history_file, persistent_history_file)
 
+        # initialize plugin system
+        # needs to be done before we call __init__(0)
+        self._initialize_plugin_system()
+
         # Call super class constructor
         super().__init__(completekey=completekey, stdin=stdin, stdout=stdout)
 
@@ -1670,7 +1674,7 @@ class Cmd(cmd.Cmd):
         statement = self.statement_parser.parse_command_only(line)
         return statement.command, statement.args, statement.command_and_args
 
-    def onecmd_plus_hooks(self, line):
+    def onecmd_plus_hooks(self, line: str) -> bool:
         """Top-level function called by cmdloop() to handle parsing a line and running the command and all of its hooks.
 
         :param line: str - line of text read from input
@@ -1680,9 +1684,17 @@ class Cmd(cmd.Cmd):
         stop = False
         try:
             statement = self._complete_statement(line)
-            (stop, statement) = self.postparsing_precmd(statement)
+            # call the postparsing hooks
+            for func in self._postparsing_hooks:
+                (stop, statement) = func(statement)
+                if stop:
+                    break
+            if not stop:
+                (stop, statement) = self.postparsing_precmd(statement)
             if stop:
-                return self.postparsing_postcmd(stop)
+                # we need to not run the command, but
+                # we need to run the finalization hooks
+                raise EmptyStatement
 
             try:
                 if self.allow_redirection:
@@ -1690,9 +1702,20 @@ class Cmd(cmd.Cmd):
                 timestart = datetime.datetime.now()
                 if self._in_py:
                     self._last_result = None
+
+                # precommand hooks
+                for func in self._precmd_hooks:
+                    statement = func(statement)
                 statement = self.precmd(statement)
+
+                # go run the command function
                 stop = self.onecmd(statement)
+
+                # postcommand hooks
+                for func in self._postcmd_hooks:
+                    stop = func(stop, statement)
                 stop = self.postcmd(stop, statement)
+
                 if self.timing:
                     self.pfeedback('Elapsed: %s' % str(datetime.datetime.now() - timestart))
             finally:
@@ -3047,6 +3070,8 @@ Script should contain one command per line, just like command would be typed in
                 self.cmdqueue.extend(callargs)
 
         # Always run the preloop first
+        for func in self._preloop_hooks:
+            func()
         self.preloop()
 
         # If transcript-based regression testing was requested, then do that instead of the main loop
@@ -3065,8 +3090,43 @@ Script should contain one command per line, just like command would be typed in
             self._cmdloop()
 
         # Run the postloop() no matter what
+        for func in self._postloop_hooks:
+            func()
         self.postloop()
 
+    ###
+    #
+    # plugin related functions
+    #
+    ###
+    def _initialize_plugin_system(self):
+        """Initialize the plugin system"""
+        self._preloop_hooks = []
+        self._postloop_hooks = []
+        self._postparsing_hooks = []
+        self._precmd_hooks = []
+        self._postcmd_hooks = []
+
+    def register_preloop_hook(self, func):
+        """Register a function to be called at the beginning of the command loop."""
+        self._preloop_hooks.append(func)
+
+    def register_postloop_hook(self, func):
+        """Register a function to be called at the end of the command loop."""
+        self._postloop_hooks.append(func)
+
+    def register_postparsing_hook(self, func):
+        """Register a function to be called after parsing user input but before running the command"""
+        self._postparsing_hooks.append(func)
+
+    def register_precmd_hook(self, func):
+        """Register a function to be called before the command function."""
+        self._precmd_hooks.append(func)
+
+    def register_postcmd_hook(self, func):
+        """Register a function to be called after the command function."""
+        self._postcmd_hooks.append(func)
+
 
 class HistoryItem(str):
     """Class used to represent an item in the History list.