Update handle_error to be more useful

Now, local variables from the innermost frame (i.e. where the error was raised) are printed with the traceback, and the latter includes all of the call stack (instead of just up to the innermost error handler).

src/decorators.py

@@ -1,7 +1,9 @@
 import fnmatch
 import socket
 import traceback
+import threading
 import types
+import sys
 from collections import defaultdict
 
 from oyoyo.client import IRCClient
@@ -20,6 +22,14 @@ HOOKS = defaultdict(list)
 
 # Error handler decorators
 
+_do_nothing = lambda: None
+
+class _local(threading.local):
+    level = 0
+    frame_locals = None
+
+_local = _local()
+
 class handle_error:
 
     def __new__(cls, func):
@@ -36,25 +46,43 @@ class handle_error:
         return self
 
     def __call__(self, *args, **kwargs):
+        fn = _do_nothing
+        _local.level += 1
         try:
             return self.func(*args, **kwargs)
         except Exception:
-            traceback.print_exc() # no matter what, we want it to print
+            if _local.frame_locals is None:
-            if kwargs.get("cli"): # client
+                exc_type, exc_value, tb = sys.exc_info()
-                cli = kwargs["cli"]
+                while tb.tb_next is not None:
-            else:
+                    tb = tb.tb_next
-                for cli in args:
+                _local.frame_locals = tb.tb_frame.f_locals
-                    if isinstance(cli, IRCClient):
+
-                        break
+            if _local.level > 1:
-                else:
+                raise # the outermost caller should handle this
+
+            fn = lambda: errlog("\n" + data)
+            data = traceback.format_exc()
             cli = None
+            variables = ["\nLocal variables from innermost frame:\n"]
+            for name, value in _local.frame_locals.items():
+                if isinstance(value, IRCClient):
+                    cli = value
+
+                variables.append("{0} = {1!r}".format(name, value))
+
+            data += "\n".join(variables)
 
             if cli is not None:
                 if not botconfig.PASTEBIN_ERRORS or botconfig.CHANNEL != botconfig.DEV_CHANNEL:
                     cli.msg(botconfig.CHANNEL, messages["error_log"])
-                errlog(traceback.format_exc())
                 if botconfig.PASTEBIN_ERRORS and botconfig.DEV_CHANNEL:
-                    pastebin_tb(cli, messages["error_log"], traceback.format_exc())
+                    pastebin_tb(cli, messages["error_log"], data)
+
+        finally:
+            fn()
+            _local.level -= 1
+            if not _local.level: # outermost caller; we're done here
+                _local.frame_locals = None
 
 class cmd:
     def __init__(self, *cmds, raw_nick=False, flag=None, owner_only=False,