Extract refactor can produce unnecessary_parenthesis trigger

[FMorschel]

Repro:

class A {
  void a() {
    (1 + 2);
  }
}

Now select (1 + 2) and the option to Extract Method.

Output:

class A {
  void a() {
    b();
  }

  void b() => (1 + 2);   // <-- unnecessary_parenthesis
}

[dart-github-bot]

Summary: The Dart Extract Method refactoring incorrectly adds unnecessary parentheses when extracting an expression, resulting in a unnecessary_parenthesis lint warning.

[bwilkerson]

It's true that there are unnecessary parentheses in the extracted method, but there were unnecessary parentheses in the code before it was extracted. The fact that it wasn't reported is a bug in the lint (I opened dart-lang/linter#5112 to report it).

IMO, the extract method refactoring should not change the code being extracted. If there are diagnostics being reported against it, they should remain and users can fix the diagnostics separately.

[FMorschel]

I agree, but when it is a simple expression it could use the unparenthesized version. So it doesn't create new diagnostics. Say:

void foo() => (bar() + baz()) ? 0 : 1;

Even with dart-lang/linter#4996 merged, there would be no lint on (bar() + baz()) but it would trigger on the extracted code.

Sorry for the bad first example. This one is more similar to the actual code I found the behaviour.

[bwilkerson]

Understood. And I'm not saying that the refactor can't introduce a lint violation. I just think it's better if the refactoring doesn't try to fix the code. But clearly not everyone agrees with me 😄 , and that's fine.