Spring SpEL ternary and Elvis expressions are missing enclosing parentheses in toStringAST()

Affects: 5.2.23

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Hi

Today I faced with the following problem: ternary operator loses parenthesis after I call .toStringAST(). I implemented the test reproducing the bug:

        var spelExpressionParser = new SpelExpressionParser();
        var expression = (SpelExpression) spelExpressionParser.parseExpression("(a ? 1 : 0) * 10");

        assertEquals("((a ? 1 : 0) * 10)", expression.getAST().toStringAST());

And it fails with the error

org.opentest4j.AssertionFailedError: expected: <((a ? 1 : 0) * 10)> but was: <(a ? 1 : 0 * 10)>

In fact, the actual expression is different since it multiplies 0 to 10 first and then applies ternary operator

Comment From: sbrannen

Hi @MisterRnobe,

Thanks for bringing this to our attention, and congratulations on creating your first issue for the Spring Framework.

In fact, the actual expression is different since it multiplies 0 to 10 first and then applies ternary operator

The following test demonstrates that the expression is evaluated successfully, but the assertion for toStringAST() indeed fails as you pointed out.

@Test
void ternaryExpressionEnclosedInParentheses() {
    SpelExpressionParser parser = new SpelExpressionParser();
    SpelExpression expression =
        (SpelExpression) parser.parseExpression("((4 % 2 == 0) ? 2 : 1) * 10");

    assertThat(expression.getValue()).isEqualTo(20);
    assertThat(expression.getAST().toStringAST()).isEqualTo("(((4 % 2) == 0) ? 2 : 1) * 10");
}

So the issue seems to only be the output of toStringAST().

We will look into it.

Comment From: sbrannen

It turns our that Elvis expressions are also missing enclosing parentheses in the generated AST string representation, so I'll address that as well.

Comment From: sbrannen

This has been addressed in 27f3feea1a2488df17c3b6fbcbbf416768e7a5b3 for inclusion in 5.3.24 and 6.0 GA.