[Gradle] Implement IosSourceSetConventionUsedWithoutIosTarget diagnostic

... in case when iosMain, iosTest conventions are used
w/o any ios target being applied

^KT-58676 Verification Pending

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

@@ -8,16 +8,22 @@ package org.jetbrains.kotlin.gradle.dsl
 import org.gradle.api.NamedDomainObjectContainer
 import org.gradle.api.NamedDomainObjectProvider
 import org.jetbrains.kotlin.gradle.dsl.KotlinSourceSetConvention.isRegisteredByKotlinSourceSetConventionAt
-import org.jetbrains.kotlin.gradle.plugin.*
+import org.jetbrains.kotlin.gradle.plugin.KotlinDependencyHandler
+import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
+import org.jetbrains.kotlin.gradle.plugin.KotlinTarget
+import org.jetbrains.kotlin.gradle.plugin.LanguageSettingsBuilder
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinGradleProjectChecker
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinGradleProjectCheckerContext
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.AndroidMainSourceSetConventionUsedWithoutAndroidTarget
+import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.IosSourceSetConventionUsedWithoutIosTarget
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.PlatformSourceSetConventionUsedWithCustomTargetName
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.PlatformSourceSetConventionUsedWithoutCorrespondingTarget
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnosticsCollector
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.reportDiagnostic
+import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinNativeTarget
 import org.jetbrains.kotlin.gradle.targets.js.dsl.KotlinJsTargetDsl
 import org.jetbrains.kotlin.gradle.targets.jvm.KotlinJvmTarget
+import org.jetbrains.kotlin.konan.target.Family
 
 @KotlinGradlePluginDsl
 interface KotlinMultiplatformSourceSetConventions {
@@ -152,3 +158,24 @@ internal object AndroidMainSourceSetConventionsChecker : KotlinGradleProjectChec
         }
     }
 }
+
+internal object IosSourceSetConventionChecker : KotlinGradleProjectChecker {
+    override suspend fun KotlinGradleProjectCheckerContext.runChecks(collector: KotlinToolingDiagnosticsCollector) {
+        val kotlin = project.multiplatformExtensionOrNull ?: return
+
+        val iosSourceSets = listOf("iosMain", "iosTest")
+            .mapNotNull { sourceSetName -> kotlin.awaitSourceSets().findByName(sourceSetName) }
+            .filter { it.isRegisteredByKotlinSourceSetConventionAt != null }
+
+
+        val hasIosTarget = kotlin.awaitTargets()
+            .any { target -> target is KotlinNativeTarget && target.konanTarget.family == Family.IOS }
+
+        if (!hasIosTarget) {
+            iosSourceSets.forEach { sourceSet ->
+                project.reportDiagnostic(IosSourceSetConventionUsedWithoutIosTarget(sourceSet))
+            }
+        }
+
+    }
+}

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

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.gradle.plugin.diagnostics
 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.plugin.KotlinPluginLifecycle
@@ -112,6 +113,7 @@ internal interface KotlinGradleProjectChecker {
             KotlinSourceSetTreeDependsOnMismatchChecker,
             PlatformSourceSetConventionsChecker,
             AndroidMainSourceSetConventionsChecker,
+            IosSourceSetConventionChecker
         )
     }
 }

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

@@ -425,7 +425,28 @@ object KotlinToolingDiagnostics {
                 |    kotlin {
                 |        androidTarget() /* <- register the androidTarget */
                 |    }
-            """.trimMargin()
+            """.trimMargin(),
+            throwable = sourceSet.isRegisteredByKotlinSourceSetConventionAt
+        )
+    }
+
+    object IosSourceSetConventionUsedWithoutIosTarget : ToolingDiagnosticFactory(WARNING) {
+        operator fun invoke(sourceSet: KotlinSourceSet) = build(
+            """
+                |Accessed '$sourceSet' without registering any ios target:
+                |  kotlin {
+                |     /* Register at least one of the following targets */
+                |     iosX64()
+                |     iosArm64()
+                |     iosSimulatorArm64()
+                |     
+                |     /* Use convention
+                |     sourceSets.${sourceSet.name}.dependencies {
+                |     
+                |     }
+                |  }
+            """.trimMargin(),
+            throwable = sourceSet.isRegisteredByKotlinSourceSetConventionAt
         )
     }
 

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

@@ -7,6 +7,8 @@
 
 package org.jetbrains.kotlin.gradle.unitTests.diagnosticsTests
 
+import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformSourceSetConventionsImpl.iosMain
+import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformSourceSetConventionsImpl.iosTest
 import org.jetbrains.kotlin.gradle.dsl.multiplatformExtension
 import org.jetbrains.kotlin.gradle.plugin.configurationResult
 import org.jetbrains.kotlin.gradle.util.buildProjectWithMPP
@@ -86,4 +88,16 @@ class MppSourceSetConventionsDiagnosticTests {
             checkDiagnostics("AndroidMainSourceSetConventionUsedWithoutAndroidTarget")
         }
     }
+
+    @Test
+    fun `test - iosMain and iosTest - without any ios target`() = buildProjectWithMPP().runLifecycleAwareTest {
+        multiplatformExtension.linuxX64()
+        multiplatformExtension.jvm()
+
+        multiplatformExtension.sourceSets.iosMain
+        multiplatformExtension.sourceSets.iosTest
+
+        configurationResult.await()
+        checkDiagnostics("IosSourceSetConventionUsedWithoutIosTarget")
+    }
 }

libraries/tools/kotlin-gradle-plugin/src/functionalTest/resources/expectedDiagnostics/IosSourceSetConventionUsedWithoutIosTarget.txt

@@ -0,0 +1,31 @@
+[IosSourceSetConventionUsedWithoutIosTarget | WARNING] Accessed 'source set iosMain' without registering any ios target:
+  kotlin {
+     /* Register at least one of the following targets */
+     iosX64()
+     iosArm64()
+     iosSimulatorArm64()
+
+     /* Use convention
+     sourceSets.iosMain.dependencies {
+
+     }
+  }
+----
+[IosSourceSetConventionUsedWithoutIosTarget | WARNING] Accessed 'source set iosTest' without registering any ios target:
+  kotlin {
+     /* Register at least one of the following targets */
+     iosX64()
+     iosArm64()
+     iosSimulatorArm64()
+
+     /* Use convention
+     sourceSets.iosTest.dependencies {
+
+     }
+  }
+----
+[UnusedSourceSetsWarning | WARNING] The following Kotlin source sets were configured but not added to any Kotlin compilation:
+ * iosMain
+ * iosTest
+You can add a source set to a target's compilation by connecting it with the compilation's default source set using 'dependsOn'.
+See https://kotl.in/connecting-source-sets