Merge pull request #5771 from denis-zhdanov/BAEL-2373-kotlin-contracts
BAEL-2373 Kotlin Contracts
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package com.baeldung.contract
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import kotlin.contracts.ExperimentalContracts
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import kotlin.contracts.InvocationKind
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import kotlin.contracts.contract
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@ExperimentalContracts
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inline fun <R> myRun(block: () -> R): R {
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contract {
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callsInPlace(block, InvocationKind.EXACTLY_ONCE)
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}
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return block()
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}
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@ExperimentalContracts
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fun callsInPlace() {
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val i: Int
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myRun {
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i = 1 // Without contract initialization is forbidden due to possible re-assignment
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}
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println(i) // Without contract variable might be uninitialized
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}
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package com.baeldung.contract
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import kotlin.contracts.ExperimentalContracts
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import kotlin.contracts.contract
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data class Request(val arg: String)
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class Service {
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@ExperimentalContracts
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fun process(request: Request?) {
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validate(request)
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println(request.arg)
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}
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}
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@ExperimentalContracts
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private fun validate(request: Request?) {
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contract {
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returns() implies (request != null)
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}
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if (request == null) {
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throw IllegalArgumentException("Undefined request")
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}
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}
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data class MyEvent(val message: String)
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@ExperimentalContracts
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fun processEvent(event: Any?) {
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if (isInterested(event)) {
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println(event.message) // Compiler makes smart cast here with the help of contract
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}
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}
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@ExperimentalContracts
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fun isInterested(event: Any?): Boolean {
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contract {
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returns(true) implies (event is MyEvent)
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}
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return event is MyEvent
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}
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@ -202,7 +202,7 @@
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</build>
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<properties>
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<kotlin.version>1.3.0</kotlin.version>
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<kotlin.version>1.3.10</kotlin.version>
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<kotlinx.version>1.0.0</kotlinx.version>
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<ktor.io.version>0.9.5</ktor.io.version>
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<assertj.version>3.11.0</assertj.version>
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