[GROOVY-10936] Patterns conditionally created using pattern operator ~ are cast to String/GString

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0.7, 4.0.8, 4.0.9
• Fix Version/s: 3.0.20, 5.0.0-alpha-4, 4.0.17

Language

groovy

• Assignee: Eric Milles
• Reporter: Pavlo Shevchenko
• Created: 14/Feb/23 10:32
• Updated: 22/Dec/23 11:38
• Resolved: 15/Dec/23 18:29

Description

Summary

If the value of the Pattern object is based on some argument evaluated at runtime, then such objects will be created as String/GString instead of Pattern.

This used to work in 4.0.6, but started failing in 4.0.7.

Reproducer

class Reproducer {

    static void main(String... args) {
        def random = new Random()

        def staticPatternSlashy = ~/some static pattern \w+/
        def staticPatternGString = ~"some static pattern \\w+"
        def dynamicPatternSlashy = random.nextInt() % 2 == 0 ? ~/pattern one \w+/ : ~/pattern two \w+/
        def dynamicPatternGString = random.nextInt() % 2 == 0 ? ~"pattern one \\w+" : ~"pattern two \\w+"

        assert staticPatternSlashy instanceof Pattern       // succeeds
        assert staticPatternGString instanceof Pattern      // succeeds
        assert dynamicPatternSlashy instanceof Pattern      // fails
        assert dynamicPatternGString instanceof Pattern     // fails
    }

} 

Workaround

Explicitly declaring the variable as Pattern does not work and fails at runtime as it will attempt to cast the String to Pattern. Creating the pattern using Pattern.compile()  works, but is a nasty refactoring and eliminates the benefits of the operator.