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regexgoswaggernsregularexpressionqregularexpression

Regular expression to disallow empty string and comma

I'm trying to write regular expression to restrict empty string and comma inside a string

example:

string = "" # not allowed
s = "ab c!@#)(*&^%$#~" # allowed
s = "sfsfsf,sdfsdf" # not allowed

The intention of this regexp is to do a pattern matching in swagger documentation like this property: type: string pattern: "^[0-9A-Za-z_]+$" value: type: object

I tried this regular expression ^(?!\s*$)[^,]*$ but it is not supported inside swagger doc and I get this error in golang code for this regular expression:

invalid or unsupported Perl syntax: `(?!

Solution

  • You actually don't need a look ahead.

    Just remove that lookahead expression and change * to + which will require at least one character and simplify your regex to ^[^,]+$

    Let me know if that works or if you have more conditions.

    Edit:

    Considering @JvdV's comment (and he seems right), you can use following regex,

    ^\s*([^,\s]+\s*)+$

    This will match if there is at least one non whitespace character and whole string will be rejected if there is even a single occurrence of a comma

    Check this demo

    Edit1:

    To avoid catastrophic backtracking, the regex can be simplified as following,

    ^\s*[^,\s][^,]*$

    Explanation:

    • ^ - Match start of input
    • \s* - Optionally match any whitespaces
    • [^,\s] - Match at least one character other than comma and whitespace
    • [^,]* - Can be followed by any character other than comma zero or more times
    • $ - Match end of string

    Updated Demo

    Edit2: For avoiding leading/trailing whitespaces, you can use this regex,

    ^[^\s,]([^,]*[^\s,])?$

    Demo avoiding leading/trailing whitespaces