Non-encoded control characters and whitespace characters are often injected in the source code because of a bad manipulation. They are either invisible or difficult to recognize, which can result in bugs when the string is not what the developer expects. If you actually need to use a control character use their encoded version (ex: ASCII ``++\n,\t,++``... or Unicode ``++U+000D, U+0009,++``...).


This rule raises an issue when the following characters are seen in a literal string:

* https://en.wikipedia.org/wiki/ASCII#Control_characters[ASCII control character]. (character index < 32 or ++=++ 127)
* Unicode https://en.wikipedia.org/wiki/Unicode_character_property#Whitespace[whitespace characters].
* Unicode https://en.wikipedia.org/wiki/C0_and_C1_control_codes[C0 control characters]
* Unicode characters ``++U+200B, U+200C, U+200D, U+2060, U+FEFF, U+2028, U+2029++``

No issue will be raised on the simple space character. Unicode ``++U+0020++``, ASCII 32.
