Fix possible exception while formatting non-string message (#331)

CHANGELOG.rst

@@ -1,3 +1,9 @@
+`Unreleased`_
+=============
+
+- Fix possible exception during formatting of non-string messages (`#331 <https://github.com/Delgan/loguru/issues/331>`_).
+
+
 `0.5.2`_ (2020-09-06)
 =====================
 

loguru/_logger.py

@@ -1914,7 +1914,7 @@ def _log(self, level_id, static_level_no, from_decorator, options, message, args
             "function": code.co_name,
             "level": RecordLevel(level_name, level_no, level_icon),
             "line": frame.f_lineno,
-            "message": message,
+            "message": str(message),
             "module": splitext(file_name)[0],
             "name": name,
             "process": RecordProcess(process.ident, process.name),
@@ -1941,7 +1941,7 @@ def _log(self, level_id, static_level_no, from_decorator, options, message, args
             if args or kwargs:
                 colored_message = Colorizer.prepare_message(message, args, kwargs)
             else:
-                colored_message = Colorizer.prepare_simple_message(message)
+                colored_message = Colorizer.prepare_simple_message(str(message))
             log_record["message"] = colored_message.stripped
         elif args or kwargs:
             colored_message = None

tests/test_formatting.py

@@ -164,6 +164,64 @@ def sink(message):
     ]
 
 
+def test_non_string_message(writer):
+    logger.add(writer, format="{message}")
+
+    logger.info(1)
+    logger.info({})
+    logger.info(b"test")
+
+    assert writer.read() == "1\n{}\nb'test'\n"
+
+
+@pytest.mark.parametrize("colors", [True, False])
+def test_non_string_message_is_str_in_record(writer, colors):
+    output = ""
+
+    def sink(message):
+        nonlocal output
+        assert isinstance(message.record["message"], str)
+        output += message
+
+    def format(record):
+        assert isinstance(record["message"], str)
+        return "[{message}]\n"
+
+    logger.add(sink, format=format, catch=False)
+    logger.opt(colors=colors).info(123)
+    assert output == "[123]\n"
+
+
+@pytest.mark.parametrize("colors", [True, False])
+def test_missing_positional_field_during_formatting(writer, colors):
+    logger.add(writer)
+
+    with pytest.raises(IndexError):
+        logger.opt(colors=colors).info("Foo {} {}", 123)
+
+
+@pytest.mark.parametrize("colors", [True, False])
+def test_missing_named_field_during_formatting(writer, colors):
+    logger.add(writer)
+
+    with pytest.raises(KeyError):
+        logger.opt(colors=colors).info("Foo {bar}", baz=123)
+
+
+def test_not_formattable_message(writer):
+    logger.add(writer)
+
+    with pytest.raises(AttributeError):
+        logger.info(123, baz=456)
+
+
+def test_not_formattable_message_with_colors(writer):
+    logger.add(writer)
+
+    with pytest.raises(TypeError):
+        logger.opt(colors=True).info(123, baz=456)
+
+
 def test_invalid_color_markup(writer):
     with pytest.raises(ValueError):
         logger.add(writer, format="<red>Not closed tag", colorize=True)