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UnnecessaryApplySpec.kt
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UnnecessaryApplySpec.kt
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package io.gitlab.arturbosch.detekt.rules.style
import io.gitlab.arturbosch.detekt.api.Config
import io.gitlab.arturbosch.detekt.rules.KotlinCoreEnvironmentTest
import io.gitlab.arturbosch.detekt.test.compileAndLint
import io.gitlab.arturbosch.detekt.test.compileAndLintWithContext
import org.assertj.core.api.Assertions.assertThat
import org.jetbrains.kotlin.cli.jvm.compiler.KotlinCoreEnvironment
import org.junit.jupiter.api.Nested
import org.junit.jupiter.api.Test
@KotlinCoreEnvironmentTest
class UnnecessaryApplySpec(val env: KotlinCoreEnvironment) {
val subject = UnnecessaryApply(Config.empty)
@Nested
inner class `unnecessary apply expressions that can be changed to ordinary method call` {
@Test
fun `reports an apply on non-nullable type`() {
val findings = subject.compileAndLintWithContext(
env,
"""
fun f() {
val a: Int = 0
a.apply {
plus(1)
}
}
"""
)
assertThat(findings).hasSize(1)
assertThat(findings.first().message).isEqualTo("apply expression can be omitted")
}
@Test
fun `reports an apply on nullable type`() {
val findings = subject.compileAndLintWithContext(
env,
"""
fun f() {
val a: Int? = null
// Resolution: we can't say here if plus is on 'this' or just a side effect when a is not null
// However such cases should be better handled with an if-null check instead of misusing apply
a?.apply {
plus(1)
}
}
"""
)
assertThat(findings).hasSize(1)
assertThat(findings.first().message).isEqualTo("apply can be replaced with let or an if")
}
@Test
fun `reports a false negative apply on nullable type - #1485`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
val a: Any? = Any()
fun Any.b() = Unit
fun main() {
a?.apply {
b()
}
}
"""
)
).hasSize(1)
}
@Test
fun `does not report an apply with lambda block`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
fun f() {
val a: Int? = null
a?.apply({
plus(1)
})
}
"""
)
).isEmpty()
}
@Test
fun `does not report single statement in apply used as function argument`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
fun b(i: Int?) {}
fun main() {
val a: Int? = null
b(a.apply {
toString()
})
}
"""
)
).isEmpty()
}
@Test
fun `does not report single assignment statement in apply used as function argument - #1517`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C {
var prop = 0
}
fun main() {
val list = ArrayList<C>()
list.add(
if (true) {
C().apply {
prop = 1
}
} else {
C()
}
)
}
"""
)
).isEmpty()
}
@Test
fun `does not report if result of apply is used - #2938`() {
assertThat(
subject.compileAndLint(
"""
fun main() {
val a = listOf(mutableListOf(""))
.map { it.apply { add("") } }
}
"""
)
).isEmpty()
}
@Test
fun `does not report applies with lambda body containing more than one statement`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
fun b(i: Int?) {}
fun main() {
val a: Int? = null
a?.apply {
plus(1)
plus(2)
}
a?.apply {
plus(1)
plus(2)
}
b(1.apply {
plus(1)
plus(2)
})
}
"""
)
).isEmpty()
}
@Test
fun `reports when lambda has a dot qualified expression`() {
val findings = subject.compileAndLintWithContext(
env,
"""
fun test(foo: Foo) {
foo.apply {
bar.bar()
}
}
class Foo(val bar: Bar)
class Bar {
fun bar() {}
}
"""
)
assertThat(findings).hasSize(1)
}
@Test
fun `reports when lambda has a dot qualified expression which has 'this' receiver`() {
val findings = subject.compileAndLintWithContext(
env,
"""
fun test(foo: Foo) {
foo.apply {
this.bar.bar()
}
}
class Foo(val bar: Bar)
class Bar {
fun bar() {}
}
"""
)
assertThat(findings).hasSize(1)
}
@Test
fun `reports when lambda has a 'this' expression`() {
val findings = subject.compileAndLintWithContext(
env,
"""
fun test() {
"foo".apply {
this
}
}
"""
)
assertThat(findings).hasSize(1)
}
}
@Nested
inner class `unnecessary apply expressions that can be changed to assignment` {
@Test
fun `reports apply with a single assignment whose result is unused`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C {
var prop = 0
}
fun main() {
val c = C()
c.apply {
prop = 1
}
}
"""
)
).hasSize(1)
}
@Test
fun `does not report apply with a single assignment whose result is used`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C {
var prop = 0
}
fun main() {
val c = C().apply {
prop = 1
}
}
"""
)
).isEmpty()
}
}
@Nested
inner class `reported false positives - #1305` {
@Test
fun `is used within an assignment expr itself`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C {
fun f() = true
}
val a = C().apply { f() }
"""
)
).isEmpty()
}
@Test
fun `is used as return type of extension function`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C(var prop: Int)
fun Int.f() = C(5).apply { prop = 10 }
"""
)
).isEmpty()
}
@Test
fun `should not flag apply when assigning property on this`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C(var prop: Int) {
private val c by lazy {
C(1).apply { prop = 3 }
}
}
"""
)
).isEmpty()
}
@Test
fun `should not report apply when using it after returning something`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C(var prop: Int)
fun f() = (C(5)).apply { prop = 10 }
"""
)
).isEmpty()
}
@Test
fun `should not report apply usage inside safe chained expressions`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
fun f() {
val arguments = listOf(1,2,3)
?.map { it * 2 }
?.apply { if (true) 4 }
?: listOf(0)
}
"""
)
).isEmpty()
}
}
@Nested
inner class `false positive in single nesting expressions - #1473` {
@Test
fun `should not report the if expression`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C {
fun has() = true
}
fun f() {
C().apply {
if (has()) {
// actions
}
}
}
"""
)
).isEmpty()
}
@Test
fun `should report reference expressions`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C {
val prop = 5
}
fun f() {
C().apply {
prop
}
C().apply {
this.prop
}
}
"""
)
).hasSize(2)
}
}
@Nested
inner class `false positive when it's used as an expression - #2435` {
@Test
fun `do not report when it's used as an assignment`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C {
fun f() {}
}
fun main() {
val c = if (5 >= 3) {
C().apply { f() }
} else {
C()
}
}
"""
)
).isEmpty()
}
@Test
fun `do not report when it's used as the last statement of a block inside lambda`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
class C {
fun f() {}
}
fun print(block: () -> C) {
println(block())
}
fun main() {
print {
println("Does nothing")
C().apply { f() }
}
}
"""
)
).isEmpty()
}
}
@Nested
inner class `false positive when lambda has multiple member references - #3561` {
@Test
fun `do not report when lambda has multiple member references`() {
assertThat(
subject.compileAndLintWithContext(
env,
"""
fun test(foo: Foo) {
foo.apply {
bar {
baz = 2
}
}
}
class Foo {
fun bar(f: () -> Unit) {
}
var baz = 1
}
"""
)
).isEmpty()
}
}
}