Improve Kotlin/Native disabled targets warning, KT-29693

* Group all disabled targets from all subprojects in a single warning
* Make the warning optional, suggest disabling it with a Gradle property

Issue #KT-29693 Fixed

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/NewMultiplatformIT.kt

@@ -4,6 +4,8 @@
  */
 package org.jetbrains.kotlin.gradle
 
+import org.jetbrains.kotlin.gradle.internals.DISABLED_NATIVE_TARGETS_REPORTER_DISABLE_WARNING_PROPERTY_NAME
+import org.jetbrains.kotlin.gradle.internals.DISABLED_NATIVE_TARGETS_REPORTER_WARNING_PREFIX
 import org.jetbrains.kotlin.gradle.internals.GRADLE_NO_METADATA_WARNING
 import org.jetbrains.kotlin.gradle.plugin.ProjectLocalConfigurations
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinJvmWithJavaTargetPreset
@@ -1894,4 +1896,16 @@ class NewMultiplatformIT : BaseGradleIT() {
             }
         }
     }
+
+    @Test
+    fun testIgnoreDisabledNativeTargets() = with(Project("sample-lib", gradleVersion, "new-mpp-lib-and-app")) {
+        build {
+            assertSuccessful()
+            assertEquals(1, output.lines().count { DISABLED_NATIVE_TARGETS_REPORTER_WARNING_PREFIX in it })
+        }
+        build("-P$DISABLED_NATIVE_TARGETS_REPORTER_DISABLE_WARNING_PROPERTY_NAME=true") {
+            assertSuccessful()
+            assertNotContains(DISABLED_NATIVE_TARGETS_REPORTER_WARNING_PREFIX)
+        }
+    }
 }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinProperties.kt

@@ -18,6 +18,7 @@ package org.jetbrains.kotlin.gradle.plugin
 
 import org.gradle.api.Project
 import org.jetbrains.kotlin.gradle.dsl.Coroutines
+import org.jetbrains.kotlin.gradle.plugin.mpp.DisabledNativeTargetsReporter
 import org.jetbrains.kotlin.gradle.tasks.AbstractKotlinCompile
 import org.jetbrains.kotlin.gradle.tasks.Kotlin2JsCompile
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
@@ -92,6 +93,9 @@ internal class PropertiesProvider(private val project: Project) {
     val enableGranularSourceSetsMetadata: Boolean?
         get() = booleanProperty("kotlin.mpp.enableGranularSourceSetsMetadata")
 
+    val ignoreDisabledNativeTargets: Boolean?
+        get() = booleanProperty(DisabledNativeTargetsReporter.DISABLE_WARNING_PROPERTY_NAME)
+
     /**
      * Enables parallel tasks execution within a project with Workers API.
      * Does not enable using actual worker proccesses

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/native/DisabledNativeTargetsReporter.kt

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.gradle.plugin.mpp
+
+import org.gradle.api.Project
+import org.jetbrains.kotlin.gradle.plugin.PropertiesProvider
+import org.jetbrains.kotlin.konan.target.HostManager
+import org.jetbrains.kotlin.konan.target.KonanTarget
+
+internal object DisabledNativeTargetsReporter {
+    private const val EXTENSION_NAME = "org.jetbrains.kotlin.native.disabledTargets"
+
+    internal const val WARNING_PREFIX = "Some Kotlin/Native targets cannot be built on this "
+
+    internal const val DISABLE_WARNING_PROPERTY_NAME = "kotlin.native.ignoreDisabledTargets"
+
+    fun reportDisabledTarget(project: Project, target: KotlinNativeTarget, supportedHosts: Collection<KonanTarget>) {
+        val disabledTargetsList = getOrRegisterDisabledTargets(project)
+        disabledTargetsList.add(DisabledTarget(project, target, supportedHosts))
+    }
+
+    private data class DisabledTarget(val project: Project, val target: KotlinNativeTarget, val supportedHosts: Collection<KonanTarget>)
+
+    @Suppress("UNCHECKED_CAST")
+    private fun getOrRegisterDisabledTargets(project: Project) =
+        project.rootProject.extensions.run {
+            if (findByName(EXTENSION_NAME) == null) {
+                add(EXTENSION_NAME, mutableListOf<DisabledTarget>())
+                printWarningWhenTaskGraphIsReady(project)
+            }
+            getByName(EXTENSION_NAME)
+        } as MutableList<DisabledTarget>
+
+    private fun printWarningWhenTaskGraphIsReady(project: Project) {
+        project.gradle.taskGraph.whenReady {
+            if (PropertiesProvider(project).ignoreDisabledNativeTargets == true) {
+                return@whenReady
+            }
+
+            val disabledTargetsList = getOrRegisterDisabledTargets(project)
+
+            @Suppress("UselessCallOnCollection") // filterIsInstance helps against potential class loaders conflict or misconfiguration
+            val disabledTargetGroups = disabledTargetsList
+                .filterIsInstance<DisabledTarget>()
+                .groupBy { it.project }
+                .mapValues { (_, disabledTargetsInProject) -> disabledTargetsInProject.groupBy { it.supportedHosts } }
+                .toSortedMap(compareBy { it.path })
+
+            project.logger.warn(buildString {
+                appendln("\n$WARNING_PREFIX${HostManager.host} machine and are disabled:")
+
+                disabledTargetGroups.forEach { (targetProject, targetsBySupportedHosts) ->
+                    appendln(
+                        "    * In project '${targetProject.path}':"
+                    )
+                    targetsBySupportedHosts.forEach { (supportedHosts, disabledTargets) ->
+                        append("        * target" + "s".takeIf { disabledTargets.size > 1 }.orEmpty() + " ")
+                        append(disabledTargets.joinToString { "'${it.target.name}'" })
+                        
+                        val supportedHostsString = when (supportedHosts.size) {
+                            1 -> "a ${supportedHosts.single()} host"
+                            else -> "one of the hosts: ${supportedHosts.joinToString(", ")}"
+                        }
+                        appendln(" (can be built with $supportedHostsString)")
+                    }
+                }
+                appendln("To hide this message, add '$DISABLE_WARNING_PROPERTY_NAME=true' to the Gradle properties.")
+            })
+        }
+    }
+}

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/targets/native/KotlinNativeTargetPreset.kt

@@ -89,14 +89,7 @@ class KotlinNativeTargetPreset(
         if (!konanTarget.enabledOnCurrentHost) {
             with(HostManager()) {
                 val supportedHosts = enabledByHost.filterValues { konanTarget in it }.keys
-                val supportedHostsString =
-                    if (supportedHosts.size == 1)
-                        "a ${supportedHosts.single()} host" else
-                        "one of the host platforms: ${supportedHosts.joinToString(", ")}"
-                project.logger.warn(
-                    "Target '$name' for platform ${konanTarget} is ignored during build on this ${HostManager.host} machine. " +
-                            "You can build it with $supportedHostsString."
-                )
+                DisabledNativeTargetsReporter.reportDisabledTarget(project, result, supportedHosts)
             }
         }
 

libraries/tools/kotlin-gradle-plugin/src/test/kotlin/org/jetbrains/kotlin/gradle/internals/ExposedForIntegrationTests.kt

@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.gradle.internals
 
+import org.jetbrains.kotlin.gradle.plugin.mpp.DisabledNativeTargetsReporter
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinProjectStructureMetadata
 import org.w3c.dom.Document
 
@@ -15,4 +16,10 @@ const val MULTIPLATFORM_PROJECT_METADATA_FILE_NAME =
     org.jetbrains.kotlin.gradle.plugin.mpp.MULTIPLATFORM_PROJECT_METADATA_FILE_NAME
 
 const val GRADLE_NO_METADATA_WARNING =
-    org.jetbrains.kotlin.gradle.plugin.mpp.KotlinMultiplatformPlugin.GRADLE_NO_METADATA_WARNING
+    org.jetbrains.kotlin.gradle.plugin.mpp.KotlinMultiplatformPlugin.GRADLE_NO_METADATA_WARNING
+
+const val DISABLED_NATIVE_TARGETS_REPORTER_DISABLE_WARNING_PROPERTY_NAME =
+    DisabledNativeTargetsReporter.DISABLE_WARNING_PROPERTY_NAME
+
+const val DISABLED_NATIVE_TARGETS_REPORTER_WARNING_PREFIX: String =
+    DisabledNativeTargetsReporter.WARNING_PREFIX