Parameters with regular expressions starting or ending with a space

Symptoms

1. A text parameter with regular expression validation is created.
2. The regular expression is set to a. I.e., it starts and ends with a space.
3. When starting a build and specifying the value for this parameter, the value a fails the validation, but a gets validated successfully.

Cause

If the regular expression starts and/or ends with a space, such spaces are trimmed.

Resolution

Use \s token for validating spaces at the start or end of the parameter's value. For example, if the regular expression is set to \sa\s, then only a value will pass the validation.