[Gradle] Add KotlinSourceSetDependsOnDefaultCompilationSourceSet diagnostic

Default Kotlin Source sets should not have any dependents.

^KT-47144 Verification Pending

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

@@ -354,6 +354,16 @@ object KotlinToolingDiagnostics {
             }
         }
     }
+
+    object KotlinSourceSetDependsOnDefaultCompilationSourceSet : ToolingDiagnosticFactory(WARNING) {
+        operator fun invoke(dependeeName: String, dependencyName: String) = build(
+            """
+                Kotlin Source Set '$dependeeName' can't depend on '$dependencyName' which is a default source set for compilation.
+                None of source sets can depend on the compilation default source sets.
+                Please remove this dependency edge.
+            """.trimIndent()
+        )
+    }
 }
 
 private fun String.indentLines(nSpaces: Int = 4, skipFirstLine: Boolean = true): String {

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

@@ -9,6 +9,7 @@ import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 import org.jetbrains.kotlin.gradle.plugin.KotlinTargetHierarchy.SourceSetTree
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinGradleProjectChecker
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinGradleProjectCheckerContext
+import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.KotlinSourceSetDependsOnDefaultCompilationSourceSet
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.KotlinSourceSetTreeDependsOnMismatch
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnosticsCollector
 import org.jetbrains.kotlin.gradle.plugin.mpp.KotlinMetadataTarget
@@ -53,6 +54,8 @@ internal object KotlinSourceSetTreeDependsOnMismatchChecker : KotlinGradleProjec
             }
         }
 
+        reportAllDependentsOfLeafSourceSets(collector, leafSourceSets.keys, reverseSourceSetDependencies)
+
         for ((badSourceSet, _) in badSourceSets) {
             val dependents = reverseSourceSetDependencies[badSourceSet].orEmpty()
 
@@ -63,11 +66,8 @@ internal object KotlinSourceSetTreeDependsOnMismatchChecker : KotlinGradleProjec
             // until underlying dependent source sets relations are fixed
             if (dependents.any { it in badSourceSets }) continue
 
-            // If [badSourceSet] is also a leaf source set then all its dependents edges are incorrect
-            // Therefore report everything that depend on the leaf source set (i.e. iosX64Test -> iosX64Main)
-            // NB: Cyclic diagnostics such as iosX64Main -> commonMain -> iosX64Main is handled in [AbstractKotlinSourceSet::dependsOn]
             if (badSourceSet in leafSourceSets) {
-                dependents.forEach { collector.report(project, KotlinSourceSetTreeDependsOnMismatch(it.name, badSourceSet.name)) }
+                // It should be reported in [reportAllDependentsOfLeafSourceSets]
                 continue
             }
 
@@ -105,6 +105,22 @@ internal object KotlinSourceSetTreeDependsOnMismatchChecker : KotlinGradleProjec
         }
     }
 
+    private fun KotlinGradleProjectCheckerContext.reportAllDependentsOfLeafSourceSets(
+        collector: KotlinToolingDiagnosticsCollector,
+        leafSourceSets: Set<KotlinSourceSet>,
+        reverseSourceSetDependencies: Map<KotlinSourceSet, Set<KotlinSourceSet>>,
+    ) {
+        for (leafSourceSet in leafSourceSets) {
+            val dependents = reverseSourceSetDependencies[leafSourceSet].orEmpty()
+            for (dependent in dependents) {
+                collector.report(
+                    project,
+                    KotlinSourceSetDependsOnDefaultCompilationSourceSet(dependent.name, leafSourceSet.name)
+                )
+            }
+        }
+    }
+
     private fun KotlinGradleProjectCheckerContext.reportSingleSourceSetWithDifferentSourceSetTree(
         collector: KotlinToolingDiagnosticsCollector,
         badSourceSet: KotlinSourceSet,

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

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.gradle.unitTests.diagnosticsTests
 
 import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.KotlinSourceSetTreeDependsOnMismatch
+import org.jetbrains.kotlin.gradle.plugin.diagnostics.KotlinToolingDiagnostics.KotlinSourceSetDependsOnDefaultCompilationSourceSet
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.ToolingDiagnostic
 import org.jetbrains.kotlin.gradle.plugin.diagnostics.kotlinToolingDiagnosticsCollector
 import org.jetbrains.kotlin.gradle.util.*
@@ -27,9 +28,13 @@ class KotlinSourceSetTreeDependsOnMismatchTest {
             }
         }
         project.evaluate()
+        val expectedDiagnosticsIds = listOf(
+            KotlinSourceSetTreeDependsOnMismatch.id,
+            KotlinSourceSetDependsOnDefaultCompilationSourceSet.id
+        )
         return project.kotlinToolingDiagnosticsCollector
             .getDiagnosticsForProject(project)
-            .filter { it.id == KotlinSourceSetTreeDependsOnMismatch.id } // ignore other diagnostics that can appear as well
+            .filter { it.id in expectedDiagnosticsIds } // ignore other diagnostics that can appear as well
     }
 
     private fun checkSingleBadSourceSetDependency(
@@ -86,13 +91,31 @@ class KotlinSourceSetTreeDependsOnMismatchTest {
     @Test
     fun `iosX64Test cant depend on iosX64Main`() = checkSingleBadSourceSetDependency(
         dependent = "iosX64Test",
-        dependency = "iosX64Main"
+        dependency = "iosX64Main",
+        KotlinSourceSetDependsOnDefaultCompilationSourceSet(dependeeName = "iosX64Test", dependencyName = "iosX64Main")
     )
 
     @Test
     fun `iosX64Main cant depend on iosX64Test`() = checkSingleBadSourceSetDependency(
         dependent = "iosX64Main",
-        dependency = "iosX64Test"
+        dependency = "iosX64Test",
+        KotlinSourceSetDependsOnDefaultCompilationSourceSet(dependeeName = "iosX64Main", dependencyName = "iosX64Test")
+    )
+
+    @Test
+    fun `iosX64Main cant depend on iosArm64Main`() = checkSingleBadSourceSetDependency(
+        dependent = "iosX64Main",
+        dependency = "iosArm64Main",
+        KotlinSourceSetDependsOnDefaultCompilationSourceSet(dependeeName = "iosX64Main", dependencyName = "iosArm64Main")
+    )
+
+    @Test
+    fun `iosX64Main cant depend on iosArm64Main -- mixed scenario`() = checkDiagnostics {
+        sourceSets.getByName("iosX64Main").dependsOn(sourceSets.getByName("iosArm64Main"))
+        sourceSets.getByName("iosArm64Test").dependsOn(sourceSets.getByName("iosArm64Main"))
+    }.assertDiagnostics(
+        KotlinSourceSetDependsOnDefaultCompilationSourceSet(dependeeName = "iosArm64Test", dependencyName = "iosArm64Main"),
+        KotlinSourceSetDependsOnDefaultCompilationSourceSet(dependeeName = "iosX64Main", dependencyName = "iosArm64Main")
     )
 
     @Test