fix: fix quoting for backslash escaping

Author: spaceone

src/logfmter/formatter.py

@@ -60,13 +60,14 @@ def format_string(cls, value: str) -> str:
         """
         needs_dquote_escaping = '"' in value
         needs_newline_escaping = "\n" in value
+        needs_backslash_escaping = "\\" in value
         needs_quoting = (
             " " in value
             or "=" in value
             or needs_dquote_escaping
             or needs_newline_escaping
+            or needs_backslash_escaping
         )
-        needs_backslash_escaping = "\\" in value and needs_quoting
 
         if needs_backslash_escaping:
             value = value.replace("\\", "\\\\")

tests/test_formatter.py

@@ -26,9 +26,10 @@
     ("\n\n", '"\\n\\n"'),
     # If the string contains a backslash and needs to be quoted, then
     # the backslashes need to be escaped.
-    ("\\", "\\"),
+    ("\\", r'"\\"'),
     ("\\ ", '"\\\\ "'),
     ('\\"', '"\\\\\\""'),
+    ("\\n", r'"\\n"'),
 ]
 
 TYPE_CONVERSION_RULES = [