[Gradle] Report KotlinTargetAlreadyDeclared from checker

Rephrase diagnostic message and add kotl.in link for details.

^KT-59316 Verification Pending

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinMultiplatformExtension.kt

@@ -14,11 +14,8 @@ import org.jetbrains.kotlin.gradle.InternalKotlinGradlePluginApi
 import org.jetbrains.kotlin.gradle.plugin.*
 import org.jetbrains.kotlin.gradle.plugin.KotlinPluginLifecycle.Stage.AfterFinaliseDsl
 import org.jetbrains.kotlin.gradle.plugin.PropertiesProvider.Companion.kotlinPropertiesProvider
-import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.KotlinTargetAlreadyDeclared
-import org.jetbrains.kotlin.gradle.plugin.diagnostics.kotlinToolingDiagnosticsCollector
 import org.jetbrains.kotlin.gradle.plugin.hierarchy.KotlinHierarchyDslImpl
 import org.jetbrains.kotlin.gradle.plugin.mpp.*
-import org.jetbrains.kotlin.gradle.targets.js.ir.KotlinJsIrTargetPreset
 import javax.inject.Inject
 
 @Suppress("DEPRECATION")
@@ -217,9 +214,6 @@ internal fun <T : KotlinTarget> KotlinTargetsContainerWithPresets.configureOrCre
         }
 
         existingTarget == null -> {
-            if (this is KotlinMultiplatformExtension) {
-                project.reportIfTargetOfTheSameTypeAlreadyCreated(targets, targetPreset, targetName)
-            }
             val newTarget = targetPreset.createTarget(targetName)
             targets.add(newTarget)
             configure(newTarget)
@@ -237,20 +231,3 @@ internal fun <T : KotlinTarget> KotlinTargetsContainerWithPresets.configureOrCre
     }
 }
 
-private fun Project.reportIfTargetOfTheSameTypeAlreadyCreated(
-    targets: NamedDomainObjectCollection<KotlinTarget>,
-    preset: KotlinTargetPreset<*>,
-    targetName: String,
-) {
-    val existingTargets = targets.matching { it.preset?.name == preset.name }
-    val targetDslFunctionName = when(preset) {
-        is KotlinJsIrTargetPreset -> "js"
-        is KotlinJsTargetPreset -> "js"
-        is KotlinAndroidTargetPreset -> "androidTarget"
-        else -> preset.name
-    }
-    if (existingTargets.isNotEmpty()) {
-        kotlinToolingDiagnosticsCollector.report(this, KotlinTargetAlreadyDeclared(targetDslFunctionName, targetName, Throwable()))
-    }
-}
-

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

@@ -9,8 +9,8 @@ import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.jetbrains.kotlin.gradle.dsl.AndroidMainSourceSetConventionsChecker
 import org.jetbrains.kotlin.gradle.dsl.IosSourceSetConventionChecker
-import org.jetbrains.kotlin.gradle.dsl.PlatformSourceSetConventionsChecker
 import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
+import org.jetbrains.kotlin.gradle.dsl.PlatformSourceSetConventionsChecker
 import org.jetbrains.kotlin.gradle.plugin.KotlinPluginLifecycle
 import org.jetbrains.kotlin.gradle.plugin.PropertiesProvider
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.checkers.*
@@ -114,6 +114,7 @@ internal interface KotlinGradleProjectChecker {
             PlatformSourceSetConventionsChecker,
             AndroidMainSourceSetConventionsChecker,
             IosSourceSetConventionChecker,
+            KotlinTargetAlreadyDeclaredChecker,
         )
     }
 }

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

@@ -548,27 +548,15 @@ object KotlinToolingDiagnostics {
     }
 
     object KotlinTargetAlreadyDeclared : ToolingDiagnosticFactory(WARNING) {
-        operator fun invoke(targetDslFunctionName: String, targetName: String, trace: Throwable?) = build(
+        operator fun invoke(targetDslFunctionName: String) = build(
             """
                 Kotlin Target '$targetDslFunctionName()' is already declared.
-                Declaring multiple Kotlin Targets of the same type is deprecated.
+
+                Declaring multiple Kotlin Targets of the same type is not recommended
+                and will become an error in the upcoming Kotlin releases.
                 
-                i.e.
-                    kotlin {
-                        $targetDslFunctionName()                       
-                        $targetDslFunctionName("$targetName") /* <- second '$targetDslFunctionName' target in the project is deprecated */
-                    }
-                    
-                Please use different Gradle Projects or create Kotlin Compilations.
-                For example:
-                
-                    kotlin {
-                        $targetDslFunctionName() {
-                            val $targetName by compilations.creating                           
-                        }
-                    }
-            """.trimIndent(),
-            throwable = trace
+                Read https://kotl.in/04i2n7 for details.
+            """.trimIndent()
         )
     }
 }

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

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2010-2023 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.diagnostics.checkers
+
+import org.jetbrains.kotlin.gradle.plugin.KotlinTarget
+import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinGradleProjectChecker
+import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinGradleProjectCheckerContext
+import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.KotlinTargetAlreadyDeclared
+import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnosticsCollector
+import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinAndroidTargetPreset
+import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinJsTargetPreset
+import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinMetadataTarget
+import org.jetbrains.kotlin.gradle.targets.js.ir.KotlinJsIrTargetPreset
+
+internal object KotlinTargetAlreadyDeclaredChecker : KotlinGradleProjectChecker {
+    override suspend fun KotlinGradleProjectCheckerContext.runChecks(collector: KotlinToolingDiagnosticsCollector) {
+        val targets = multiplatformExtension?.awaitTargets() ?: return
+        val duplicatedTargets = targets
+            .filter { it !is KotlinMetadataTarget }
+            .groupBy { it.preset?.name }
+            .filterValues { it.size > 1 }
+
+        for (targetsGroup in duplicatedTargets.values) {
+            val targetDslFunctionName = targetsGroup.first()
+                .targetDslFunctionName
+                // skip targets without known dsl function such as external targets
+                ?: continue
+
+            collector.report(project, KotlinTargetAlreadyDeclared(targetDslFunctionName))
+        }
+    }
+
+    /**
+     * DSL names are taken from [org.jetbrains.kotlin.gradle.dsl.KotlinTargetContainerWithPresetFunctions]
+     */
+    private val KotlinTarget.targetDslFunctionName
+        get() = when (preset) {
+            is KotlinJsIrTargetPreset -> "js"
+            is KotlinJsTargetPreset -> "js"
+            is KotlinAndroidTargetPreset -> "androidTarget"
+            else -> preset?.name
+        }
+}

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

@@ -67,10 +67,7 @@ class KotlinTargetAlreadyDeclaredTest {
         }
 
         project.evaluate()
-        project.assertContainsDiagnostic(
-            KotlinTargetAlreadyDeclared("jvm", "jvm2", null),
-            ignoreThrowable = true
-        )
+        project.assertContainsDiagnostic(KotlinTargetAlreadyDeclared("jvm"))
     }
 
     @Test
@@ -83,10 +80,7 @@ class KotlinTargetAlreadyDeclaredTest {
         }
 
         project.evaluate()
-        project.assertContainsDiagnostic(
-            KotlinTargetAlreadyDeclared("linuxArm64", "linux", null),
-            ignoreThrowable = true
-        )
+        project.assertContainsDiagnostic(KotlinTargetAlreadyDeclared("linuxArm64"))
     }
 
     @Test
@@ -101,10 +95,7 @@ class KotlinTargetAlreadyDeclaredTest {
         }
 
         project.evaluate()
-        project.assertContainsDiagnostic(
-            KotlinTargetAlreadyDeclared("androidTarget", "android2", null),
-            ignoreThrowable = true
-        )
+        project.assertContainsDiagnostic(KotlinTargetAlreadyDeclared("androidTarget"))
     }
 
     @Test
@@ -117,9 +108,6 @@ class KotlinTargetAlreadyDeclaredTest {
         }
 
         project.evaluate()
-        project.assertContainsDiagnostic(
-            KotlinTargetAlreadyDeclared("js", "nodejs", null),
-            ignoreThrowable = true
-        )
+        project.assertContainsDiagnostic(KotlinTargetAlreadyDeclared("js"))
     }
 }