Don't null check a mutable property

[BraisGabin]

Expected Behavior of the rule

non compliant:

class A(
    var foo: Asdf?
) {
  fun bar() {
    if (foo != null) {
      foo!!.toString()
      doThings(foo!!.value)
    }
  }
}

compliant:

class A(
    var foo: Asdf?
) {
  fun bar() {
    val foo = foo // or use let, or whatever you want
    if (foo != null) {
      foo.toString()
      doThings(foo.value)
    }
  }
}

Context

#3352 is the example that make me think about this rule. This is a pattern that I see often in the my project. Usually this errors happens when you translates code from Java to Kotlin.

Maybe we could check this kind of things too:
non compliant:

class A {
  fun getActivity(): Activity? = // whatever

  fun bar() {
    if (getActivity() != null) {
      getActivity()!!.doSomething()
    }
  }
}

compliant:

class A {
  fun getActivity(): Activity? = // whatever

  fun bar() {
    val activity = getActivity() // or ?.let or whatever you want
    if (activity != null) {
      .doSomething()
    }
  }
}

This pattern is kind of usual in Android because the framework give us this kind of APIs. But I don't think that this as an Android specific rule.

[cortinico]

non compliant:

class A(
    var foo: Asdf?
) {
  fun bar() {
    if (foo != null) {
      foo!!.toString()
      doThings(foo!!.value)
    }
  }
}

I believe the root of this rule should be "don't null check a mutable property". The multiple !! (or whatever null checks) are needed as foo is a nullable mutable property, and therefore checking if it's not null won't suffice to smart cast it to a Asdf.

[github-actions]

This issue is stale because it has been open 90 days with no activity. Please comment or this will be closed in 7 days.

[atulgpt]

Hi, @BraisGabin I think this issue got fixed by the above PR. right?

[BraisGabin]

Nice spot! Closing :)