[RFC] Allow to configure exception formatter

loguru/_handler.py

@@ -93,12 +93,12 @@ def emit(self, record, level_color, ansi_message, raw):
 
             formatter_record = record.copy()
 
-            if not record["exception"]:
-                error = ""
-            else:
+            if record["exception"] and self._exception_formatter:
                 type_, value, tb = record["exception"]
                 lines = self._exception_formatter.format_exception(type_, value, tb)
                 error = "".join(lines)
+            else:
+                error = ""
 
             formatter_record["exception"] = error
 

loguru/_logger.py

@@ -32,6 +32,8 @@
 
 start_time = now()
 
+UNSET = object()
+
 
 class Logger:
     """An object to dispatch logging messages to configured handlers.
@@ -163,6 +165,7 @@ def add(
         diagnose=_defaults.LOGURU_DIAGNOSE,
         enqueue=_defaults.LOGURU_ENQUEUE,
         catch=_defaults.LOGURU_CATCH,
+        exception_formatter=UNSET,
         **kwargs
     ):
         r"""Add a handler sending log messages to a sink adequately configured.
@@ -201,6 +204,8 @@ def add(
             Whether or not errors occurring while sink handles logs messages should be caught or
             not. If ``True``, an exception message is displayed on |sys.stderr| but the exception is
             not propagated to the caller, preventing your app to crash.
+        exception_formatter : |ExceptionFormatter|, optional
+            By default ``loguru._better_exceptions.ExceptionFormatter`` is used.
         **kwargs
             Additional parameters that will be passed to the sink while creating it or while
             logging messages (the exact behavior depends on the sink type).
@@ -738,18 +743,6 @@ def filter_func(r):
                 "Invalid level value, it should be a positive integer, not: %d" % levelno
             )
 
-        if isinstance(format, str):
-            formatter = format + "\n{exception}"
-            is_formatter_dynamic = False
-        elif callable(format):
-            formatter = format
-            is_formatter_dynamic = True
-        else:
-            raise ValueError(
-                "Invalid format, it should be a string or a function, not: '%s'"
-                % type(format).__name__
-            )
-
         try:
             encoding = sink.encoding
         except AttributeError:
@@ -758,10 +751,7 @@ def filter_func(r):
         if not encoding:
             encoding = "ascii"
 
-        with self._lock:
-            handler_id = next(self._handlers_count)
-            colors = [lvl.color for lvl in self._levels.values()] + [""]
-
+        if exception_formatter is UNSET:
             exception_formatter = ExceptionFormatter(
                 colorize=colorize,
                 encoding=encoding,
@@ -770,6 +760,24 @@ def filter_func(r):
                 hidden_frames_filename=self.catch.__code__.co_filename,
             )
 
+        if isinstance(format, str):
+            formatter = format
+            if exception_formatter:
+                formatter += "\n{exception}"
+            is_formatter_dynamic = False
+        elif callable(format):
+            formatter = format
+            is_formatter_dynamic = True
+        else:
+            raise ValueError(
+                "Invalid format, it should be a string or a function, not: '%s'"
+                % type(format).__name__
+            )
+
+        with self._lock:
+            handler_id = next(self._handlers_count)
+            colors = [lvl.color for lvl in self._levels.values()] + [""]
+
             handler = Handler(
                 writer=writer,
                 stopper=stopper,

tests/test_formatting.py

@@ -121,3 +121,20 @@ def test_extra_formatting(writer):
 def test_invalid_color_markup(writer):
     with pytest.raises(AnsiMarkupError):
         logger.add(writer, format="<red>Not closed tag", colorize=True)
+
+
+def test_handler_with_no_exception_formatter():
+    class Handler:
+        def write(self, message):
+            assert message == "got_exception"
+            self.passed_write = True
+
+    handler = Handler()
+    logger.add(handler, format="{message}", catch=False, exception_formatter=None)
+    assert [x._exception_formatter for x in logger._handlers.values()] == [None]
+    try:
+        raise ValueError
+    except Exception:
+        logger.exception("got_exception")
+
+    assert handler.passed_write is True