Code Inspections in RegExp

Anonymous capturing group or numeric back reference

Reports anonymous capturing groups and numeric back references in a RegExp. These are only reported when the RegExp dialect supports named group and named group references. Named groups and named back references improve code readability and are recommended to use instead. When a capture is not needed, matching can be more performant and use less memory by using a non-capturing group, i.e. (?:xxx) instead of (xxx).

Disabled

Begin or end anchor in unexpected position

Reports ^ or \A anchors not at the beginning of the pattern and $, \Z or \z anchors not at the end of the pattern. In the wrong position these RegExp anchors prevent the pattern from matching anything. In case of the ^ and $ anchors, most likely the literal character was meant and the escape forgotten.

Warning

Consecutive spaces

Reports multiple consecutive spaces in a RegExp. Because spaces are not visible by default, it can be hard to see how many spaces are required. The RegExp can be made more clear by replacing the consecutive spaces with a single space and a counted quantifier.

Warning

Duplicate branch in alternation

Reports duplicate branches in a RegExp alternation. Duplicate branches slow down matching and obscure the intent of the expression.

Warning

Duplicate character in character class

Reports duplicate characters inside a RegExp character class. Duplicate characters are unnecessary and can be removed without changing the semantics of the regex.

Warning

Empty branch in alternation

Reports empty branches in a RegExp alternation. An empty branch will only match the empty string, and in most cases that is not what is desired. This inspection will not report a single empty branch at the start or the end of an alternation.

Warning

Escaped meta character

Reports escaped meta characters. Some RegExp coding styles specify that meta characters should be placed inside a character class, to make the regular expression easier to understand. This inspection does not warn about the meta character [, ] and ^, because those would need additional escaping inside a character class.

No highlighting, only fix

Octal escape

Reports octal escapes, which are easily confused with back references. Use hexadecimal escapes to avoid confusion.

No highlighting, only fix

Redundant character escape

Reports character escapes that are replaceable with the unescaped character without a change in meaning. Note that inside the square brackets of a character class, many escapes are unnecessary that would be necessary outside of a character class.

Warning

Redundant nested character class

Reports unnecessary nested character classes.

Warning

Single character alternation

Reports single char alternation in a RegExp. It is simpler to use a character class instead. This may also provide better matching performance.

Warning

Unnecessary non-capturing group

Reports unnecessary non-capturing groups, which have no influence on the match result.

Warning