[java] UselessParentheses false positive with conditional operator

[Vampire]

Affects PMD Version: 6.11.0
Rule: UselessParentheses

Code Sample demonstrating the issue:

throw new IllegalArgumentException(String.format(
        "Unsupported client with class '%s' given",
        (discordClient == null) ? null : discordClient.getClass()));

Additionally, should we add properties to allow whitelisting some scenarios, such as this one?

while ((result instanceof CompletionException) && (cause != null)) {
    result = cause;
    cause = result.getCause();
}

Running PMD through: Gradle

[jsotuyod]

@Vampire the rule will detect any pair of parenthesis that can be removed without affecting the code's behavior. As such, this being reported is effectively ok.

As for the enhancement… I guess the thing is how far we need to go… I mean, I know people tend to have trouble remembering wether && or || takes precedence first, but how far are we gonna take it? ternaries? bit-wise operations? comparations? arithmetic operations?

I'm unsure what a sane set of properties and what scenarios they allow will be intuitive for users and reasonable to maintain.

[Vampire]

Then the rule has a false-negative instead.
In

throw new IllegalArgumentException(String.format(
        "Unsupported client with class '%s' given",
        (discordClient == null ? null : discordClient.getClass())));

useless parantheses are found, in

throw new IllegalArgumentException(String.format(
        "Unsupported client with class '%s' given",
        (discordClient == null) ? null : discordClient.getClass()));

they are not.

While I also here want the parentheses to stay for easier reading.

True, finding a sane set of what to report and what not that works for all is probably impossible. :-(

[oowekyala]

For comparison, the IntelliJ inspection has a property to ignore parentheses when the inner and outer operators have different precedences. That's is not very configurable, but it's simple and makes sense.

[jsotuyod]

Ok, that one is a FP, so I'm updating the issue. I think the enhancement needs some further discussion, so maybe we should create a separate ticket.

[Vampire]

Maybe better a separate ticket for the FP to have the discussion so far here and rename this to the enhancement request?

[adangel]

Fixed with PMD 7