fix: replace invisible control characters in keys with "_"

Fixes: #54

Author: spaceone

src/logfmter/formatter.py

@@ -40,6 +40,9 @@
 )
 REPLACEMENTS = {chr(c): f"\\u{c:04x}" for c in list(range(0x20)) + [0x7F]}
 REPLACEMENTS.update({"\n": "\\n", "\t": "\\t", "\r": "\\r"})
+KEY_REPLACEMENTS = str.maketrans(
+    {chr(c): "_" for c in list(range(0x21)) + [0x7F]} | {"\n": "\\n"}
+)
 
 
 class _DefaultFormatter(logging.Formatter):
@@ -124,7 +127,7 @@ def normalize_key(cls, key: str) -> str:
         if not key:
             return "_"
 
-        return key.replace(" ", "_").replace("\n", "\\n")
+        return key.translate(KEY_REPLACEMENTS)
 
     @classmethod
     def get_extra(cls, record: logging.LogRecord) -> dict:

tests/test_formatter.py

@@ -111,6 +111,10 @@ def test_format_params(value, expected):
         ("first name", "first_name"),
         ("", "_"),
         ("first\nname", "first\\nname"),
+        (
+            "".join(map(chr, range(128))),
+            "__________\\n______________________!\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~_",
+        ),
     ],
 )
 def test_normalize_key(value, expected):