Fix stubbing by chained calls on collections (#565)

mockk/common/src/main/kotlin/io/mockk/impl/recording/states/RecordingState.kt

@@ -62,16 +62,16 @@ abstract class RecordingState(recorder: CommonCallRecorder) : CallRecordingState
     override fun call(invocation: Invocation): Any? {
         val retType = recorder.childHinter.nextChildType { invocation.method.returnType }
         var isTemporaryMock = false
-
-        val retValue =
-            if (invocation.method.isToString()) {
-                recorder.stubRepo[invocation.self]?.toStr() ?: ""
-            } else {
-                recorder.anyValueGenerator().anyValue(retType, invocation.method.returnTypeNullable) {
-                    isTemporaryMock = true
-                    recorder.mockFactory.temporaryMock(retType)
-                }
-            }
+        val temporaryMock: () -> Any = {
+            isTemporaryMock = true
+            recorder.mockFactory.temporaryMock(retType)
+        }
+        val retValue = when {
+            invocation.method.isToString() -> recorder.stubRepo[invocation.self]?.toStr() ?: ""
+            retType in CollectionTypes -> temporaryMock()
+            else -> recorder.anyValueGenerator()
+                .anyValue(retType, invocation.method.returnTypeNullable, orInstantiateVia = temporaryMock)
+        }
 
         if (retValue == null) {
             isTemporaryMock = false
@@ -191,4 +191,14 @@ abstract class RecordingState(recorder: CommonCallRecorder) : CallRecordingState
     private fun builder(): CallRoundBuilder = callRoundBuilder
         ?: throw MockKException("Call builder is not initialized. Bad state")
 
+    private companion object {
+        private val CollectionTypes = listOf(
+            List::class,
+            Map::class,
+            Set::class,
+            ArrayList::class,
+            HashMap::class,
+            HashSet::class
+        )
+    }
 }

mockk/jvm/src/test/kotlin/io/mockk/it/CollectionChainStubbingTest.kt

@@ -0,0 +1,68 @@
+package io.mockk.it
+
+import io.mockk.every
+import io.mockk.mockk
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+// Regression tests for GitHub issue #565.
+class CollectionChainStubbingTest {
+
+    private interface ReturningCollections {
+        val list: List<Int>
+        val map: Map<String, Int>
+        val set: Set<Int>
+        val arrayList: ArrayList<Int>
+        val hashMap: Map<String, Int>
+        val hashSet: HashSet<Int>
+    }
+
+    @Test
+    fun list() {
+        val mock = mockk<ReturningCollections>()
+        every { mock.list[0] } returns 1
+
+        assertEquals(1, mock.list[0])
+    }
+
+    @Test
+    fun map() {
+        val mock = mockk<ReturningCollections>()
+        every { mock.map["foo"] } returns 1
+
+        assertEquals(1, mock.map["foo"])
+    }
+
+    @Test
+    fun set() {
+        val mock = mockk<ReturningCollections>()
+        every { mock.set.contains(1) } returns true
+
+        assertTrue(mock.set.contains(1))
+    }
+
+    @Test
+    fun arrayList() {
+        val mock = mockk<ReturningCollections>()
+        every { mock.arrayList[0] } returns 1
+
+        assertEquals(1, mock.arrayList[0])
+    }
+
+    @Test
+    fun hashMap() {
+        val mock = mockk<ReturningCollections>()
+        every { mock.hashMap["foo"] } returns 1
+
+        assertEquals(1, mock.hashMap["foo"])
+    }
+
+    @Test
+    fun hashSet() {
+        val mock = mockk<ReturningCollections>()
+        every { mock.hashSet.contains(0) } returns true
+
+        assertTrue(mock.hashSet.contains(0))
+    }
+}