Add proper error handling. Closes #151

All exceptions, if not caught, are unconditionally sent to `sys.stderr`.
We only need to use our own custom class with some modifications and we
can intercept all errors, even those in threads (which #151 was about).
The only real downside from this practice is that `cli` is not
accessible to us when the errors happen, so I used a hack to set it on
an instance variable. If anyone can find a better solution, please step
forward. For the time being, this will have to do.

If for some obscure reason this class breaks, `sys.__stderr__` holds the
original `sys.stderr`

src/__init__.py

@@ -1,6 +1,10 @@
+import traceback
 import argparse
 import datetime
+import socket
 import time
+import sys
+import io
 
 import botconfig
 import src.settings as var
@@ -104,3 +108,55 @@ def stream(output, level="normal"):
         stream_handler(output)
     elif level == "warning":
         stream_handler(output)
+
+# Error handler
+
+buffer = io.BufferedWriter(io.FileIO(file=sys.stderr.fileno(), mode="wb", closefd=False))
+
+class ErrorHandler(io.TextIOWrapper):
+    """Handle tracebacks sent to sys.stderr."""
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.cli = None
+        self.target_logger = None
+        self.data = []
+
+    def write(self, data):
+        assert not (self.cli is None or self.target_logger is None)
+        if self.closed:
+            raise ValueError("write to closed file")
+        if not isinstance(data, str):
+            raise ValueError("can't write %s to text stream" % data.__class__.__name__)
+        length = len(data)
+        b = data.encode("utf-8", "replace")
+        self.buffer.write(b)
+        self.data.append(data)
+        if data and not data.startswith(("Traceback", " ", "Exception in thread")):
+            self.flush()
+        return length
+
+    def flush(self):
+        self.buffer.flush()
+
+        msg = "An error has occurred and has been logged."
+        if not botconfig.PASTEBIN_ERRORS or botconfig.CHANNEL != botconfig.DEV_CHANNEL:
+            self.cli.msg(botconfig.CHANNEL, msg)
+        if botconfig.PASTEBIN_ERRORS and botconfig.DEV_CHANNEL:
+            try:
+                with socket.socket() as sock:
+                    sock.connect(("termbin.com", 9999))
+                    sock.send(b"".join(s.encode("utf-8", "replace") for s in self.data) + b"\n")
+                    url = sock.recv(1024).decode("utf-8")
+            except socket.error:
+                self.target_logger("".join(self.data), display=False)
+            else:
+                self.cli.msg(botconfig.DEV_CHANNEL, " ".join((msg, url)))
+        del self.data[:]
+        if var.PHASE in ("join", "day", "night"):
+            from src.decorators import COMMANDS
+            for cmd in COMMANDS["fstop"]:
+                cmd.func(self.cli, "<stderr>", "", "")
+
+sys.stderr = ErrorHandler(buffer=buffer, encoding=sys.stderr.encoding,
+             errors=sys.stderr.errors, line_buffering=sys.stderr.line_buffering)

src/handler.py

@@ -1,9 +1,9 @@
 # The bot commands implemented in here are present no matter which module is loaded
 
-import base64
-import imp
-import socket
 import traceback
+import base64
+import socket
+import sys
 
 from oyoyo.parse import parse_nick
 
@@ -14,31 +14,10 @@ from src import decorators, logger, wolfgame
 log = logger("errors.log")
 alog = logger(None)
 
+sys.stderr.target_logger = log
+
 hook = decorators.hook
 
-def notify_error(cli, chan, target_logger):
-    msg = "An error has occurred and has been logged."
-
-    tb = traceback.format_exc()
-
-    target_logger(tb)
-
-    if (not botconfig.PASTEBIN_ERRORS) or (chan != botconfig.DEV_CHANNEL):
-        # Don't send a duplicate message if DEV_CHANNEL is the current channel.
-        cli.msg(chan, msg)
-
-    if botconfig.PASTEBIN_ERRORS and botconfig.DEV_CHANNEL:
-        try:
-            with socket.socket() as sock:
-                sock.connect(("termbin.com", 9999))
-                sock.send(tb.encode("utf-8", "replace") + b"\n")
-                url = sock.recv(1024).decode("utf-8")
-        except socket.error:
-            target_logger(traceback.format_exc())
-        else:
-            cli.msg(botconfig.DEV_CHANNEL, " ".join((msg, url)))
-
-
 def on_privmsg(cli, rawnick, chan, msg, notice = False):
 
     try:
@@ -63,7 +42,7 @@ def on_privmsg(cli, rawnick, chan, msg, notice = False):
             if botconfig.DEBUG_MODE:
                 raise
             else:
-                notify_error(cli, chan, log)
+                traceback.print_exc()
 
 
     for x in decorators.COMMANDS:
@@ -83,7 +62,7 @@ def on_privmsg(cli, rawnick, chan, msg, notice = False):
                     if botconfig.DEBUG_MODE:
                         raise
                     else:
-                        notify_error(cli, chan, log)
+                        traceback.print_exc()
 
 
 def unhandled(cli, prefix, cmd, *args):
@@ -94,11 +73,11 @@ def unhandled(cli, prefix, cmd, *args):
         for fn in decorators.HOOKS.get(cmd, []):
             try:
                 fn.func(cli, prefix, *largs)
-            except Exception as e:
+            except Exception:
                 if botconfig.DEBUG_MODE:
-                    raise e
+                    raise
                 else:
-                    notify_error(cli, botconfig.CHANNEL, log)
+                    traceback.print_exc()
 
 def connect_callback(cli):
     @hook("endofmotd", hookid=294)
@@ -184,6 +163,8 @@ def connect_callback(cli):
             # capability but now claims otherwise.
             alog("Server refused capabilities: {0}".format(" ".join(caps)))
 
+    if sys.stderr.cli is None:
+        sys.stderr.cli = cli # first connection
 
     if botconfig.SASL_AUTHENTICATION:
         @hook("authenticate")

src/wolfgame.py

@@ -494,17 +494,17 @@ def forced_exit(cli, nick, chan, rest):
         try:
             stop_game(cli)
         except Exception:
-            notify_error(cli, chan, errlog)
+            traceback.print_exc()
 
     try:
         reset_modes_timers(cli)
     except Exception:
-        notify_error(cli, chan, errlog)
+        traceback.print_exc()
 
     try:
         reset()
     except Exception:
-        notify_error(cli, chan, errlog)
+        traceback.print_exc()
 
     msg = "{0} quit from {1}"
 
@@ -516,7 +516,7 @@ def forced_exit(cli, nick, chan, rest):
                             nick,
                             rest.strip()))
     except Exception:
-        notify_error(cli, chan, errlog)
+        traceback.print_exc()
         sys.exit()
 
 
@@ -540,12 +540,12 @@ def restart_program(cli, nick, chan, rest):
         try:
             stop_game(cli)
         except Exception:
-            notify_error(cli, chan, errlog)
+            traceback.print_exc()
 
     try:
         reset_modes_timers(cli)
     except Exception:
-        notify_error(cli, chan, errlog)
+        traceback.print_exc()
 
     try:
         with sqlite3.connect("data.sqlite3", check_same_thread=False) as conn:
@@ -554,12 +554,12 @@ def restart_program(cli, nick, chan, rest):
             if players:
                 c.execute("UPDATE pre_restart_state SET players = ?", (" ".join(players),))
     except Exception:
-        notify_error(cli, chan, errlog)
+        traceback.print_exc()
 
     try:
         reset()
     except Exception:
-        notify_error(cli, chan, errlog)
+        traceback.print_exc()
 
     msg = "{0} restart from {1}".format(
         "Scheduled" if restart_program.aftergame else "Forced", nick)
@@ -596,7 +596,7 @@ def restart_program(cli, nick, chan, rest):
     try:
         cli.quit(msg.format(nick, rest.strip()))
     except Exception:
-        notify_error(cli, chan, errlog)
+        traceback.print_exc()
 
     @hook("quit")
     def restart_buffer(cli, raw_nick, reason):
@@ -7508,6 +7508,9 @@ def fwait(cli, nick, chan, rest):
 @cmd("fstop", admin_only=True, phases=("join", "day", "night"))
 def reset_game(cli, nick, chan, rest):
     """Forces the game to stop."""
+    if nick == "<stderr>":
+        cli.msg(botconfig.CHANNEL, "Game stopped due to error.")
+    else:
         cli.msg(botconfig.CHANNEL, "\u0002{0}\u0002 has forced the game to stop.".format(nick))
     if var.PHASE != "join":
         stop_game(cli)