Emit a diagnostic if variant reselection is used pre Gradle 7.6

^KT-66133

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/diagnostics/KotlinToolingDiagnostics.kt

@@ -806,6 +806,17 @@ object KotlinToolingDiagnostics {
         )
     }
 
+    object ResourceMayNotBeResolvedWithGradleVersion : ToolingDiagnosticFactory(ERROR) {
+        operator fun invoke(
+            targetName: String, currentGradleVersion: String, minimumRequiredVersion: String) = build(
+            """
+            Resources for target $targetName may not be resolved. Minimum required Gradle version is ${minimumRequiredVersion} but current is ${currentGradleVersion}.
+            
+            $resourcesBugReportRequest
+            """.trimIndent()
+        )
+    }
+
     object UnknownValueProvidedForResourcesStrategy : ToolingDiagnosticFactory(ERROR) {
         operator fun invoke(value: String) = build(
             """

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/resources/GradleVersion.kt

@@ -0,0 +1,18 @@
+/*
+ * Copyright 2010-2024 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.resources
+
+import org.gradle.api.Project
+import org.gradle.util.GradleVersion
+import org.jetbrains.kotlin.gradle.plugin.extraProperties
+import org.jetbrains.kotlin.gradle.plugin.getOrNull
+
+private const val OVERRIDE_GRADLE_VERSION_FOR_TESTS = "org.jetbrains.kotlin.internal.overriddenGradleVersionForTests"
+internal var Project.overriddenGradleVersionForTests: GradleVersion?
+    set(value) = extraProperties.set(OVERRIDE_GRADLE_VERSION_FOR_TESTS, value)
+    get() = extraProperties.getOrNull(OVERRIDE_GRADLE_VERSION_FOR_TESTS) as? GradleVersion
+internal val Project.gradleVersion: GradleVersion get() = overriddenGradleVersionForTests ?: GradleVersion.current()
+

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/resources/KotlinTargetResourcesPublicationImpl.kt

@@ -8,11 +8,13 @@ package org.jetbrains.kotlin.gradle.plugin.mpp.resources
 import org.gradle.api.Project
 import org.gradle.api.provider.Provider
 import org.gradle.api.tasks.TaskProvider
+import org.gradle.util.GradleVersion
 import org.jetbrains.kotlin.gradle.plugin.*
 import org.jetbrains.kotlin.gradle.plugin.KotlinPluginLifecycle
 import org.jetbrains.kotlin.gradle.plugin.PropertiesProvider.Companion.kotlinPropertiesProvider
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.reportDiagnostic
+import org.jetbrains.kotlin.gradle.plugin.diagnostics.reportDiagnosticOncePerBuild
 import org.jetbrains.kotlin.gradle.plugin.launchInStage
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinAndroidTarget
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinNativeTarget
@@ -29,7 +31,7 @@ import java.io.File
 import javax.inject.Inject
 
 internal abstract class KotlinTargetResourcesPublicationImpl @Inject constructor(
-    val project: Project
+    private val project: Project,
 ) : KotlinTargetResourcesPublication {
 
     internal data class TargetResources(
@@ -126,9 +128,8 @@ internal abstract class KotlinTargetResourcesPublicationImpl @Inject constructor
     }
 
     override fun resolveResources(target: KotlinTarget): Provider<File> {
-        if (!canResolveResources(target)) {
+        validateTargetResourcesAreResolvable(target)
-            target.project.reportDiagnostic(KotlinToolingDiagnostics.ResourceMayNotBeResolvedForTarget(target.name))
+        validateGradleVersionIsCompatibleWithResolutionStrategy(target.name)
-        }
 
         val aggregateResourcesTaskName = target.disambiguateName("AggregateResources")
         project.locateTask<AggregateResourcesTask>(aggregateResourcesTaskName)?.let {
@@ -201,12 +202,34 @@ internal abstract class KotlinTargetResourcesPublicationImpl @Inject constructor
         }
     }
 
+    private fun validateTargetResourcesAreResolvable(target: KotlinTarget) {
+        if (!canResolveResources(target)) {
+            target.project.reportDiagnostic(KotlinToolingDiagnostics.ResourceMayNotBeResolvedForTarget(target.name))
+        }
+    }
+
+    private fun validateGradleVersionIsCompatibleWithResolutionStrategy(targetName: String) {
+        if (project.kotlinPropertiesProvider.mppResourcesResolutionStrategy == KotlinTargetResourcesResolutionStrategy.VariantReselection) {
+            if (project.gradleVersion < minimumGradleVersionForVariantReselection) {
+                project.reportDiagnosticOncePerBuild(
+                    KotlinToolingDiagnostics.ResourceMayNotBeResolvedWithGradleVersion(
+                        targetName,
+                        GradleVersion.current().toString(),
+                        minimumGradleVersionForVariantReselection.toString(),
+                    )
+                )
+            }
+        }
+    }
+
     internal companion object {
         const val MULTIPLATFORM_RESOURCES_DIRECTORY = "kotlin-multiplatform-resources"
         const val RESOURCES_CLASSIFIER = "kotlin_resources"
         const val RESOURCES_ZIP_EXTENSION = "${RESOURCES_CLASSIFIER}.zip"
 
         const val RESOURCES_PATH = "ResourcesPath"
+
+        val minimumGradleVersionForVariantReselection = GradleVersion.version("7.6")
     }
 
 }

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/resources/resourcesPublicationExtension.kt

@@ -16,7 +16,10 @@ internal val KotlinMultiplatformExtension.resourcesPublicationExtension: KotlinT
     get() {
         if (!project.kotlinPropertiesProvider.mppResourcesPublication) return null
         return project.extraProperties.getOrPut(KotlinTargetResourcesPublication.EXTENSION_NAME) {
-            project.objects.newInstance(KotlinTargetResourcesPublicationImpl::class.java, project)
+            project.objects.newInstance(
+                KotlinTargetResourcesPublicationImpl::class.java,
+                project,
+            )
         }
     }
 

libraries/tools/kotlin-gradle-plugin/src/functionalTest/kotlin/org/jetbrains/kotlin/gradle/unitTests/KotlinTargetResourcesPublicationImplTests.kt

@@ -10,12 +10,15 @@ package org.jetbrains.kotlin.gradle.unitTests
 import com.android.build.gradle.LibraryExtension
 import org.gradle.api.Project
 import org.gradle.api.internal.project.ProjectInternal
+import org.gradle.util.GradleVersion
 import org.jetbrains.kotlin.gradle.dsl.multiplatformExtension
 import org.jetbrains.kotlin.gradle.plugin.KotlinTarget
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.ToolingDiagnosticFactory
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinAndroidTarget
 import org.jetbrains.kotlin.gradle.plugin.mpp.resources.KotlinTargetResourcesPublication
+import org.jetbrains.kotlin.gradle.plugin.mpp.resources.overriddenGradleVersionForTests
+import org.jetbrains.kotlin.gradle.plugin.mpp.resources.resolve.KotlinTargetResourcesResolutionStrategy
 import org.jetbrains.kotlin.gradle.plugin.mpp.resources.resourcesPublicationExtension
 import org.jetbrains.kotlin.gradle.targets.js.dsl.ExperimentalWasmDsl
 import org.jetbrains.kotlin.gradle.util.*
@@ -164,6 +167,43 @@ class KotlinTargetResourcesPublicationImplTests {
         }
     }
 
+    @Test
+    fun `test resolution - emits diagnostic in first resolving project with variant reselection - when Gradle version is below 7_6`() {
+        val rootProject = buildProjectWithMPP(
+            projectBuilder = { withName("root") },
+            preApplyCode = {
+                setMppResourcesResolutionStrategy(KotlinTargetResourcesResolutionStrategy.VariantReselection)
+                overriddenGradleVersionForTests = GradleVersion.version("7.5.1")
+            },
+        ) { kotlin { linuxArm64() } }
+        val childProject = buildProjectWithMPP(
+            projectBuilder = { withParent(rootProject).withName("child") },
+            preApplyCode = {
+                setMppResourcesResolutionStrategy(KotlinTargetResourcesResolutionStrategy.VariantReselection)
+                overriddenGradleVersionForTests = GradleVersion.version("7.5.1")
+            },
+        ) { kotlin { linuxArm64() } }
+
+        childProject.multiplatformExtension.resourcesPublicationExtension?.resolveResources(childProject.multiplatformExtension.linuxArm64())
+        rootProject.multiplatformExtension.resourcesPublicationExtension?.resolveResources(rootProject.multiplatformExtension.linuxArm64())
+
+        childProject.assertContainsDiagnostic(KotlinToolingDiagnostics.ResourceMayNotBeResolvedWithGradleVersion)
+        rootProject.assertNoDiagnostics(KotlinToolingDiagnostics.ResourceMayNotBeResolvedWithGradleVersion)
+    }
+
+    @Test
+    fun `test resolution - doesn't emit diagnostic with variant reselection - when Gradle version is above 7_6`() {
+        buildProjectWithMPP(
+            preApplyCode = { overriddenGradleVersionForTests = GradleVersion.version("7.6.1") }
+        ) {
+            setMppResourcesResolutionStrategy(KotlinTargetResourcesResolutionStrategy.VariantReselection)
+            kotlin {
+                linuxArm64()
+                resourcesPublicationExtension?.resolveResources(linuxArm64())
+            }
+        }.assertNoDiagnostics()
+    }
+
     private fun testCallbacksAfterApiCall(
         callback: ((Unit) -> Unit) -> Unit,
         apiCall: (Unit) -> Unit,