How to use Result.mapError method of io.kotest.common.results class

1package io.kotest.engine.spec2import io.kotest.common.mapError3import io.kotest.core.config.ExtensionRegistry4import io.kotest.core.extensions.Extension5import io.kotest.core.extensions.SpecExtension6import io.kotest.core.listeners.AfterSpecListener7import io.kotest.core.listeners.BeforeSpecListener8import io.kotest.core.listeners.FinalizeSpecListener9import io.kotest.core.listeners.IgnoredSpecListener10import io.kotest.core.listeners.InstantiationErrorListener11import io.kotest.core.listeners.InstantiationListener12import io.kotest.core.listeners.PrepareSpecListener13import io.kotest.core.listeners.SpecInstantiationListener14import io.kotest.core.spec.Spec15import io.kotest.core.spec.functionOverrideCallbacks16import io.kotest.core.test.TestCase17import io.kotest.core.test.TestResult18import io.kotest.engine.extensions.ExtensionException19import io.kotest.engine.extensions.MultipleExceptions20import io.kotest.mpp.Logger21import io.kotest.mpp.bestName22import kotlin.reflect.KClass23/**24 * Used to invoke extension points / listeners / callbacks on specs.25 */26internal class SpecExtensions(private val registry: ExtensionRegistry) {27   private val logger = Logger(SpecExtensions::class)28   /**29    * Returns all [Extension]s applicable to a [Spec]. This includes extensions via30    * function overrides, those registered explicitly in the spec as part of the DSL,31    * and project wide extensions from configuration.32    */33   fun extensions(spec: Spec): List<Extension> {34      return spec.extensions() + // overriding the extensions function in the spec35         spec.listeners() + // overriding the listeners function in the spec36         spec.functionOverrideCallbacks() + // dsl37         spec.registeredExtensions() + // added to the spec via register38         registry.all() // globals39   }40   suspend fun beforeSpec(spec: Spec): Result<Spec> {41      logger.log { Pair(spec::class.bestName(), "beforeSpec $spec") }42      val errors = extensions(spec).filterIsInstance<BeforeSpecListener>().mapNotNull { ext ->43         runCatching { ext.beforeSpec(spec) }44            .mapError { ExtensionException.BeforeSpecException(it) }.exceptionOrNull()45      }46      return when {47         errors.isEmpty() -> Result.success(spec)48         errors.size == 1 -> Result.failure(errors.first())49         else -> Result.failure(MultipleExceptions(errors))50      }51   }52   /**53    * Runs all the after spec listeners for this [Spec]. All errors are caught and wrapped54    * in [AfterSpecListener] and if more than one error, all will be returned as a [MultipleExceptions].55    */56   suspend fun afterSpec(spec: Spec): Result<Spec> = runCatching {57      logger.log { Pair(spec::class.bestName(), "afterSpec $spec") }58      spec.registeredAutoCloseables().let { closeables ->59         logger.log { Pair(spec::class.bestName(), "Closing ${closeables.size} autocloseables [$closeables]") }60         closeables.forEach {61            if(it.isInitialized()) it.value.close() else Unit62         }63      }64      val errors = extensions(spec).filterIsInstance<AfterSpecListener>().mapNotNull { ext ->65         runCatching { ext.afterSpec(spec) }66            .mapError { ExtensionException.AfterSpecException(it) }.exceptionOrNull()67      }68      return when {69         errors.isEmpty() -> Result.success(spec)70         errors.size == 1 -> Result.failure(errors.first())71         else -> Result.failure(MultipleExceptions(errors))72      }73   }74   suspend fun specInstantiated(spec: Spec) = runCatching {75      logger.log { Pair(spec::class.bestName(), "specInstantiated $spec") }76      registry.all().filterIsInstance<SpecInstantiationListener>().forEach { it.specInstantiated(spec) }77      registry.all().filterIsInstance<InstantiationListener>().forEach { it.specInstantiated(spec) }78   }79   suspend fun specInstantiationError(kclass: KClass<out Spec>, t: Throwable) = runCatching {80      logger.log { Pair(kclass.bestName(), "specInstantiationError $t") }81      registry.all().filterIsInstance<SpecInstantiationListener>().forEach { it.specInstantiationError(kclass, t) }82      registry.all().filterIsInstance<InstantiationErrorListener>().forEach { it.instantiationError(kclass, t) }83   }84   suspend fun prepareSpec(kclass: KClass<out Spec>): Result<KClass<*>> {85      val exts = registry.all().filterIsInstance<PrepareSpecListener>()86      logger.log { Pair(kclass.bestName(), "prepareSpec (${exts.size})") }87      val errors = exts.mapNotNull {88         runCatching { it.prepareSpec(kclass) }89            .mapError { ExtensionException.PrepareSpecException(it) }.exceptionOrNull()90      }91      return when {92         errors.isEmpty() -> Result.success(kclass)93         errors.size == 1 -> Result.failure(errors.first())94         else -> Result.failure(MultipleExceptions(errors))95      }96   }97   suspend fun finalizeSpec(98      kclass: KClass<out Spec>,99      results: Map<TestCase, TestResult>,100      t: Throwable?101   ): Result<KClass<out Spec>> {102      val exts = registry.all().filterIsInstance<FinalizeSpecListener>()103      logger.log { Pair(kclass.bestName(), "finishSpec (${exts.size}) results:$results") }104      val errors = exts.mapNotNull {105         runCatching { it.finalizeSpec(kclass, results) }106            .mapError { ExtensionException.FinalizeSpecException(it) }.exceptionOrNull()107      }108      return when {109         errors.isEmpty() -> Result.success(kclass)110         errors.size == 1 -> Result.failure(errors.first())111         else -> Result.failure(MultipleExceptions(errors))112      }113   }114   suspend fun <T> intercept(spec: Spec, f: suspend () -> T): T? {115      val exts = extensions(spec).filterIsInstance<SpecExtension>()116      logger.log { Pair(spec::class.bestName(), "Intercepting spec with ${exts.size} spec extensions") }117      var result: T? = null118      val initial: suspend () -> Unit = {119         result = f()120      }121      val chain = exts.foldRight(initial) { op, acc ->122         {123            op.intercept(spec::class) {124               op.intercept(spec) {125                  acc()126               }127            }128         }129      }130      chain.invoke()131      return result132   }133   /**134    * Notify all [IgnoredSpecListener]s that the given [kclass] has been ignored.135    */136   suspend fun ignored(kclass: KClass<out Spec>, reason: String?): Result<KClass<out Spec>> {137      val exts = registry.all().filterIsInstance<IgnoredSpecListener>()138      logger.log { Pair(kclass.bestName(), "ignored ${exts.size} extensions on $kclass") }139      val errors = exts.mapNotNull {140         runCatching { it.ignoredSpec(kclass, reason) }141            .mapError { ExtensionException.IgnoredSpecException(it) }.exceptionOrNull()142      }143      return when {144         errors.isEmpty() -> Result.success(kclass)145         errors.size == 1 -> Result.failure(errors.first())146         else -> Result.failure(MultipleExceptions(errors))147      }148   }149}...

1fun <E, A> Result<E, A>.mapError(f: (E) -> E): Result<E, A> = when (this) {2is Failure -> Failure(f(e))3}4fun <E, A> Result<E, A>.mapError(f: (E) -> E): Result<E, A> = when (this) {5is Failure -> Failure(f(e))6}7fun <E, A> Result<E, A>.mapError(f: (E) -> E): Result<E, A> = when (this) {8is Failure -> Failure(f(e))9}10fun <E, A> Result<E, A>.mapError(f: (E) -> E): Result<E, A> = when (this) {11is Failure -> Failure(f(e))12}13fun <E, A> Result<E, A>.mapError(f: (E) -> E): Result<E, A> = when (this) {14is Failure -> Failure(f(e))15}16fun <E, A> Result<E, A>.mapError(f: (E) -> E): Result<E, A> = when (this) {17is Failure -> Failure(f(e))18}19fun <E, A> Result<E, A>.mapError(f: (E) -> E): Result<E, A> = when (this) {20is Failure -> Failure(f(e))21}22fun <E, A> Result<E, A>.mapError(f: (E) -> E): Result<E, A> = when (this) {23is Failure -> Failure(f(e))24}

1val result = Result.failure("error")2val mappedResult = result.mapError { "mapped $it" }3mappedResult shouldBe Result.failure("mapped error")4val result = Result.failure("error")5val mappedResult = result.mapError { "mapped $it" }6mappedResult shouldBe Result.failure("mapped error")7val result = Result.failure("error")8val mappedResult = result.mapError { "mapped $it" }9mappedResult shouldBe Result.failure("mapped error")10val result = Result.failure("error")11val mappedResult = result.mapError { "mapped $it" }12mappedResult shouldBe Result.failure("mapped error")13val result = Result.failure("error")14val mappedResult = result.mapError { "mapped $it" }15mappedResult shouldBe Result.failure("mapped error")16val result = Result.failure("error")17val mappedResult = result.mapError { "mapped $it" }18mappedResult shouldBe Result.failure("mapped error")19val result = Result.failure("error")20val mappedResult = result.mapError { "mapped $it" }21mappedResult shouldBe Result.failure("mapped error")22val result = Result.failure("error")23val mappedResult = result.mapError { "mapped $it" }24mappedResult shouldBe Result.failure("mapped error")25val result = Result.failure("error")26val mappedResult = result.mapError { "mapped $it" }27mappedResult shouldBe Result.failure("mapped error")28val result = Result.failure("error")29val mappedResult = result.mapError { "mapped $it" }30mappedResult shouldBe Result.failure("mapped error")31val result = Result.failure("error")32val mappedResult = result.mapError { "mapped

1val result = Result.failure ( "error" )2val mappedResult = result . mapError { it . length }3mappedResult . shouldBe ( Result . Failure ( 5 ))4val result = Result . success ( 5 )5val mappedResult = result . mapError { it . length }6mappedResult . shouldBe ( Result . Success ( 5 ))7val result = Result . failure ( "error" )8val mappedResult = result . mapError { it . length }9mappedResult . shouldBe ( Result . Failure ( 5 ))10val result = Result . success ( 5 )11val mappedResult = result . mapError { it . length }12mappedResult . shouldBe ( Result . Success ( 5 ))13val result = Result . failure ( "error" )14val mappedResult = result . mapError { it . length }15mappedResult . shouldBe ( Result . Failure ( 5 ))16val result = Result . success ( 5 )17val mappedResult = result . mapError { it . length }18mappedResult . shouldBe ( Result . Success ( 5 ))19val result = Result . failure ( "error" )20val mappedResult = result . mapError { it . length }21mappedResult . shouldBe ( Result . Failure ( 5 ))22val result = Result . success ( 5 )23val mappedResult = result . mapError { it . length }24mappedResult . shouldBe ( Result . Success ( 5 ))25val result = Result . failure ( "error" )26val mappedResult = result . mapError { it . length }27mappedResult . shouldBe ( Result . Failure ( 5 ))28val result = Result . success ( 5 )29val mappedResult = result . mapError { it . length }

1    Result.success(1).mapError { "failed" } shouldBe Result.success(1)2    Result.failure("failed").mapError { "failed again" } shouldBe Result.failure("failed again")3    Result.success(1).mapError { "failed" } shouldBe Result.success(1)4    Result.failure("failed").mapError { "failed again" } shouldBe Result.failure("failed again")5    Result.success(1).mapError { "failed" } shouldBe Result.success(1)6    Result.failure("failed").mapError { "failed again" } shouldBe Result.failure("failed again")7    Result.success(1).mapError { "failed" } shouldBe Result.success(1)8    Result.failure("failed").mapError { "failed again" } shouldBe Result.failure("failed again")9    Result.success(1).mapError { "failed" } shouldBe Result.success(1)10    Result.failure("failed").mapError { "failed again" } shouldBe Result.failure("failed again")11    Result.success(1).mapError { "failed" } shouldBe Result.success(1)12    Result.failure("failed").mapError { "failed again" } shouldBe Result.failure("failed again")13    Result.success(1).mapError { "failed" } shouldBe Result.success(1)14    Result.failure("failed").mapError { "failed again" } shouldBe Result.failure("failed again")