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Add compiler contracts

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See: https://kotlinlang.org/docs/reference/whatsnew13.html#contracts
This commit is contained in:
Michael Bull 2019-08-09 21:53:52 +01:00
parent e609f061ac
commit 66f1122efb
11 changed files with 186 additions and 18 deletions
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6
build.gradle.kts
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@ -1,7 +1,6 @@
import com.jfrog.bintray.gradle.BintrayExtension
import com.jfrog.bintray.gradle.tasks.BintrayUploadTask
import org.jetbrains.dokka.gradle.DokkaTask
import org.jetbrains.kotlin.gradle.plugin.KotlinPluginWrapper
import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
@ -22,9 +21,10 @@ allprojects {
jcenter()
}
plugins.withType<KotlinPluginWrapper> {
tasks.withType<KotlinCompile> {
kotlinOptions.jvmTarget = "1.8"
kotlinOptions {
jvmTarget = "1.8"
freeCompilerArgs = listOf("-Xuse-experimental=kotlin.contracts.ExperimentalContracts")
}
}
}

11
src/main/kotlin/com/github/michaelbull/result/And.kt
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@ -1,5 +1,8 @@
package com.github.michaelbull.result
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract
@Deprecated("Use lazy-evaluating variant instead", ReplaceWith("and { result }"))
infix fun <V, E> Result<V, E>.and(result: Result<V, E>): Result<V, E> {
return and { result }
@ -11,6 +14,10 @@ infix fun <V, E> Result<V, E>.and(result: Result<V, E>): Result<V, E> {
* - Rust: [Result.and](https://doc.rust-lang.org/std/result/enum.Result.html#method.and)
*/
inline infix fun <V, E> Result<V, E>.and(result: () -> Result<V, E>): Result<V, E> {
contract {
callsInPlace(result, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> result()
is Err -> this
@ -25,6 +32,10 @@ inline infix fun <V, E> Result<V, E>.and(result: () -> Result<V, E>): Result<V,
* - Rust: [Result.and_then](https://doc.rust-lang.org/std/result/enum.Result.html#method.and_then)
*/
inline infix fun <V, E, U> Result<V, E>.andThen(transform: (V) -> Result<U, E>): Result<U, E> {
contract {
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> transform(value)
is Err -> this

29
src/main/kotlin/com/github/michaelbull/result/Get.kt
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@ -1,5 +1,8 @@
package com.github.michaelbull.result
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract
/**
* Returns the [value][Ok.value] if this [Result] is [Ok], otherwise `null`.
*
@ -7,6 +10,11 @@ package com.github.michaelbull.result
* - Rust: [Result.ok](https://doc.rust-lang.org/std/result/enum.Result.html#method.ok)
*/
fun <V, E> Result<V, E>.get(): V? {
contract {
returnsNotNull() implies (this@get is Ok<V>)
returns(null) implies (this@get is Err<E>)
}
return when (this) {
is Ok -> value
is Err -> null
@ -19,6 +27,11 @@ fun <V, E> Result<V, E>.get(): V? {
* - Rust: [Result.err](https://doc.rust-lang.org/std/result/enum.Result.html#method.err)
*/
fun <V, E> Result<V, E>.getError(): E? {
contract {
returns(null) implies (this@getError is Ok<V>)
returnsNotNull() implies (this@getError is Err<E>)
}
return when (this) {
is Ok -> null
is Err -> error
@ -41,6 +54,10 @@ infix fun <V, E> Result<V, E>.getOr(default: V): V {
* @return The [value][Ok.value] if [Ok], otherwise [default].
*/
inline infix fun <V, E> Result<V, E>.getOr(default: () -> V): V {
contract {
callsInPlace(default, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> value
is Err -> default()
@ -61,6 +78,10 @@ infix fun <V, E> Result<V, E>.getErrorOr(default: E): E {
* @return The [error][Err.error] if [Err], otherwise [default].
*/
inline infix fun <V, E> Result<V, E>.getErrorOr(default: () -> E): E {
contract {
callsInPlace(default, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> default()
is Err -> error
@ -75,6 +96,10 @@ inline infix fun <V, E> Result<V, E>.getErrorOr(default: () -> E): E {
* - Rust: [Result.unwrap_or_else](https://doc.rust-lang.org/src/core/result.rs.html#735-740)
*/
inline infix fun <V, E> Result<V, E>.getOrElse(transform: (E) -> V): V {
contract {
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> value
is Err -> transform(error)
@ -86,6 +111,10 @@ inline infix fun <V, E> Result<V, E>.getOrElse(transform: (E) -> V): V {
* [transformation][transform] of the [value][Ok.value].
*/
inline infix fun <V, E> Result<V, E>.getErrorOrElse(transform: (V) -> E): E {
contract {
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> transform(value)
is Err -> error

45
src/main/kotlin/com/github/michaelbull/result/Map.kt
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@ -1,5 +1,8 @@
package com.github.michaelbull.result
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract
/**
* Maps this [Result<V, E>][Result] to [Result<U, E>][Result] by either applying the [transform]
* function to the [value][Ok.value] if this [Result] is [Ok], or returning this [Err].
@ -9,6 +12,10 @@ package com.github.michaelbull.result
* - Rust: [Result.map](https://doc.rust-lang.org/std/result/enum.Result.html#method.map)
*/
inline infix fun <V, E, U> Result<V, E>.map(transform: (V) -> U): Result<U, E> {
contract {
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> Ok(transform(value))
is Err -> this
@ -24,6 +31,10 @@ inline infix fun <V, E, U> Result<V, E>.map(transform: (V) -> U): Result<U, E> {
* - Rust: [Result.map_err](https://doc.rust-lang.org/std/result/enum.Result.html#method.map_err)
*/
inline infix fun <V, E, F> Result<V, E>.mapError(transform: (E) -> F): Result<V, F> {
contract {
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> this
is Err -> Err(transform(error))
@ -54,10 +65,12 @@ inline infix fun <V, E, U> Result<Iterable<V>, E>.mapAll(transform: (V) -> Resul
* - Elm: [Result.Extra.mapBoth](http://package.elm-lang.org/packages/elm-community/result-extra/2.2.0/Result-Extra#mapBoth)
* - Haskell: [Data.Either.either](https://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Either.html#v:either)
*/
inline fun <V, E, U> Result<V, E>.mapBoth(
success: (V) -> U,
failure: (E) -> U
): U {
inline fun <V, E, U> Result<V, E>.mapBoth(success: (V) -> U, failure: (E) -> U): U {
contract {
callsInPlace(success, InvocationKind.AT_MOST_ONCE)
callsInPlace(failure, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> success(value)
is Err -> failure(error)
@ -74,10 +87,12 @@ inline fun <V, E, U> Result<V, E>.mapBoth(
* - Elm: [Result.Extra.mapBoth](http://package.elm-lang.org/packages/elm-community/result-extra/2.2.0/Result-Extra#mapBoth)
* - Haskell: [Data.Either.either](https://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Either.html#v:either)
*/
inline fun <V, E, U> Result<V, E>.fold(
success: (V) -> U,
failure: (E) -> U
): U {
inline fun <V, E, U> Result<V, E>.fold(success: (V) -> U, failure: (E) -> U): U {
contract {
callsInPlace(success, InvocationKind.AT_MOST_ONCE)
callsInPlace(failure, InvocationKind.AT_MOST_ONCE)
}
return mapBoth(success, failure)
}
@ -87,10 +102,12 @@ inline fun <V, E, U> Result<V, E>.fold(
*
* - Haskell: [Data.Bifunctor.Bimap](https://hackage.haskell.org/package/base-4.10.0.0/docs/Data-Bifunctor.html#v:bimap)
*/
inline fun <V, E, U, F> Result<V, E>.mapEither(
success: (V) -> U,
failure: (E) -> F
): Result<U, F> {
inline fun <V, E, U, F> Result<V, E>.mapEither(success: (V) -> U, failure: (E) -> F): Result<U, F> {
contract {
callsInPlace(success, InvocationKind.AT_MOST_ONCE)
callsInPlace(failure, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> Ok(success(value))
is Err -> Err(failure(error))
@ -106,5 +123,9 @@ inline fun <V, E, U, F> Result<V, E>.mapEither(
* - Scala: [Either.flatMap](http://www.scala-lang.org/api/2.12.0/scala/util/Either.html#flatMap[AA>:A,Y](f:B=>scala.util.Either[AA,Y]):scala.util.Either[AA,Y])
*/
inline infix fun <V, E, U> Result<V, E>.flatMap(transform: (V) -> Result<U, E>): Result<U, E> {
contract {
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return andThen(transform)
}

11
src/main/kotlin/com/github/michaelbull/result/On.kt
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@ -1,9 +1,16 @@
package com.github.michaelbull.result
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract
/**
* Invokes an [action] if this [Result] is [Ok].
*/
inline infix fun <V, E> Result<V, E>.onSuccess(action: (V) -> Unit): Result<V, E> {
contract {
callsInPlace(action, InvocationKind.AT_MOST_ONCE)
}
if (this is Ok) {
action(value)
}
@ -15,6 +22,10 @@ inline infix fun <V, E> Result<V, E>.onSuccess(action: (V) -> Unit): Result<V, E
* Invokes an [action] if this [Result] is [Err].
*/
inline infix fun <V, E> Result<V, E>.onFailure(action: (E) -> Unit): Result<V, E> {
contract {
callsInPlace(action, InvocationKind.AT_MOST_ONCE)
}
if (this is Err) {
action(error)
}

15
src/main/kotlin/com/github/michaelbull/result/Or.kt
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@ -1,5 +1,8 @@
package com.github.michaelbull.result
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract
@Deprecated("Use lazy-evaluating variant instead", ReplaceWith("or { result }"))
infix fun <V, E> Result<V, E>.or(result: Result<V, E>): Result<V, E> {
return or { result }
@ -11,6 +14,10 @@ infix fun <V, E> Result<V, E>.or(result: Result<V, E>): Result<V, E> {
* - Rust: [Result.or](https://doc.rust-lang.org/std/result/enum.Result.html#method.or)
*/
inline infix fun <V, E> Result<V, E>.or(result: () -> Result<V, E>): Result<V, E> {
contract {
callsInPlace(result, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> this
is Err -> result()
@ -24,6 +31,10 @@ inline infix fun <V, E> Result<V, E>.or(result: () -> Result<V, E>): Result<V, E
* - Rust: [Result.or_else](https://doc.rust-lang.org/std/result/enum.Result.html#method.or_else)
*/
inline infix fun <V, E> Result<V, E>.orElse(transform: (E) -> Result<V, E>): Result<V, E> {
contract {
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> this
is Err -> transform(error)
@ -35,6 +46,10 @@ inline infix fun <V, E> Result<V, E>.orElse(transform: (E) -> Result<V, E>): Res
* otherwise this [Ok].
*/
inline infix fun <V, E> Result<V, E>.recover(transform: (E) -> V): Ok<V> {
contract {
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
is Ok -> this
is Err -> Ok(transform(error))

7
src/main/kotlin/com/github/michaelbull/result/Result.kt
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@ -1,5 +1,8 @@
package com.github.michaelbull.result
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract
/**
* [Result] is a type that represents either success ([Ok]) or failure ([Err]).
*
@ -39,6 +42,10 @@ data class Err<out E>(val error: E) : Result<Nothing, E>()
* non-null, otherwise the supplied [error].
*/
inline infix fun <V, E> V?.toResultOr(error: () -> E): Result<V, E> {
contract {
callsInPlace(error, InvocationKind.AT_MOST_ONCE)
}
return when (this) {
null -> Err(error())
else -> Ok(this)

29
src/main/kotlin/com/github/michaelbull/result/Unwrap.kt
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@ -1,5 +1,8 @@
package com.github.michaelbull.result
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract
class UnwrapException(message: String) : Exception(message)
/**
@ -10,6 +13,10 @@ class UnwrapException(message: String) : Exception(message)
* @throws UnwrapException if the [Result] is an [Err], with a message containing the [error][Err.error].
*/
fun <V, E> Result<V, E>.unwrap(): V {
contract {
returns() implies (this@unwrap is Ok<V>)
}
return when (this) {
is Ok -> value
is Err -> throw UnwrapException("called Result.wrap on an Err value $error")
@ -18,6 +25,10 @@ fun <V, E> Result<V, E>.unwrap(): V {
@Deprecated("Use lazy-evaluating variant instead", ReplaceWith("expect { message }"))
infix fun <V, E> Result<V, E>.expect(message: String): V {
contract {
returns() implies (this@expect is Ok<V>)
}
return expect { message }
}
@ -30,6 +41,11 @@ infix fun <V, E> Result<V, E>.expect(message: String): V {
* @throws UnwrapException if the [Result] is an [Err], with the specified [message].
*/
inline infix fun <V, E> Result<V, E>.expect(message: () -> Any): V {
contract {
callsInPlace(message, InvocationKind.AT_MOST_ONCE)
returns() implies (this@expect is Ok<V>)
}
return when (this) {
is Ok -> value
is Err -> throw UnwrapException("${message()} $error")
@ -44,6 +60,10 @@ inline infix fun <V, E> Result<V, E>.expect(message: () -> Any): V {
* @throws UnwrapException if the [Result] is [Ok], with a message containing the [value][Ok.value].
*/
fun <V, E> Result<V, E>.unwrapError(): E {
contract {
returns() implies (this@unwrapError is Err<E>)
}
return when (this) {
is Ok -> throw UnwrapException("called Result.unwrapError on an Ok value $value")
is Err -> error
@ -52,6 +72,10 @@ fun <V, E> Result<V, E>.unwrapError(): E {
@Deprecated("Use lazy-evaluating variant instead", ReplaceWith("expectError { message }"))
infix fun <V, E> Result<V, E>.expectError(message: String): E {
contract {
returns() implies (this@expectError is Err<E>)
}
return expectError { message }
}
@ -64,6 +88,11 @@ infix fun <V, E> Result<V, E>.expectError(message: String): E {
* @throws UnwrapException if the [Result] is [Ok], with the specified [message].
*/
inline infix fun <V, E> Result<V, E>.expectError(message: () -> Any): E {
contract {
callsInPlace(message, InvocationKind.AT_MOST_ONCE)
returns() implies (this@expectError is Err<E>)
}
return when (this) {
is Ok -> throw UnwrapException("${message()} $value")
is Err -> error

33
src/main/kotlin/com/github/michaelbull/result/Zip.kt
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@ -1,5 +1,8 @@
package com.github.michaelbull.result
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract
private typealias Producer<T, E> = () -> Result<T, E>
/**
@ -13,6 +16,12 @@ inline fun <T1, T2, E, V> zip(
result2: Producer<T2, E>,
transform: (T1, T2) -> V
): Result<V, E> {
contract {
callsInPlace(result1, InvocationKind.EXACTLY_ONCE)
callsInPlace(result2, InvocationKind.AT_MOST_ONCE)
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return result1().flatMap { v1 ->
result2().map { v2 ->
transform(v1, v2)
@ -32,6 +41,13 @@ inline fun <T1, T2, T3, E, V> zip(
result3: Producer<T3, E>,
transform: (T1, T2, T3) -> V
): Result<V, E> {
contract {
callsInPlace(result1, InvocationKind.EXACTLY_ONCE)
callsInPlace(result2, InvocationKind.AT_MOST_ONCE)
callsInPlace(result3, InvocationKind.AT_MOST_ONCE)
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return result1().flatMap { v1 ->
result2().flatMap { v2 ->
result3().map { v3 ->
@ -54,6 +70,14 @@ inline fun <T1, T2, T3, T4, E, V> zip(
result4: Producer<T4, E>,
transform: (T1, T2, T3, T4) -> V
): Result<V, E> {
contract {
callsInPlace(result1, InvocationKind.EXACTLY_ONCE)
callsInPlace(result2, InvocationKind.AT_MOST_ONCE)
callsInPlace(result3, InvocationKind.AT_MOST_ONCE)
callsInPlace(result4, InvocationKind.AT_MOST_ONCE)
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return result1().flatMap { v1 ->
result2().flatMap { v2 ->
result3().flatMap { v3 ->
@ -79,6 +103,15 @@ inline fun <T1, T2, T3, T4, T5, E, V> zip(
result5: Producer<T5, E>,
transform: (T1, T2, T3, T4, T5) -> V
): Result<V, E> {
contract {
callsInPlace(result1, InvocationKind.EXACTLY_ONCE)
callsInPlace(result2, InvocationKind.AT_MOST_ONCE)
callsInPlace(result3, InvocationKind.AT_MOST_ONCE)
callsInPlace(result4, InvocationKind.AT_MOST_ONCE)
callsInPlace(result5, InvocationKind.AT_MOST_ONCE)
callsInPlace(transform, InvocationKind.AT_MOST_ONCE)
}
return result1().flatMap { v1 ->
result2().flatMap { v2 ->
result3().flatMap { v3 ->

12
src/test/kotlin/com/github/michaelbull/result/ResultIteratorTest.kt
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@ -1,6 +1,10 @@
package com.github.michaelbull.result
import kotlin.test.*
import kotlin.test.Test
import kotlin.test.assertEquals
import kotlin.test.assertFailsWith
import kotlin.test.assertFalse
import kotlin.test.assertTrue
class ResultIteratorTest {
class HasNext {
@ -36,7 +40,11 @@ class ResultIteratorTest {
@Test
fun throwsExceptionIfUnyieldedAndErr() {
val iterator = Err("hello").iterator()
assertFailsWith<NoSuchElementException> { iterator.next() }
assertFailsWith<NoSuchElementException> {
@Suppress("IMPLICIT_NOTHING_AS_TYPE_PARAMETER")
iterator.next()
}
}
@Test

4
src/test/kotlin/com/github/michaelbull/result/UnwrapTest.kt
View File

@ -17,6 +17,7 @@ class UnwrapTest {
@Test
fun throwsExceptionIfErr() {
assertFailsWith<UnwrapException>("called Result.wrap on an Err value 5000") {
@Suppress("IMPLICIT_NOTHING_AS_TYPE_PARAMETER")
Err(5000).unwrap()
}
}
@ -38,6 +39,7 @@ class UnwrapTest {
}
assertFailsWith<UnwrapException>("the year should be 1994") {
@Suppress("IMPLICIT_NOTHING_AS_TYPE_PARAMETER")
Err(1994).expect { message }
}
}
@ -47,6 +49,7 @@ class UnwrapTest {
@Test
fun throwsExceptionIfOk() {
assertFailsWith<UnwrapException>("called Result.unwrapError on an Ok value example") {
@Suppress("IMPLICIT_NOTHING_AS_TYPE_PARAMETER")
Ok("example").unwrapError()
}
}
@ -68,6 +71,7 @@ class UnwrapTest {
}
assertFailsWith<UnwrapException>("the year should be 2010") {
@Suppress("IMPLICIT_NOTHING_AS_TYPE_PARAMETER")
Ok(2010).expectError { message }
}
}