1 files changed, 112 insertions, 0 deletions
diff --git a/formats/json-tests/jvmTest/src/kotlinx/serialization/JavaCollectionsTest.kt b/formats/json-tests/jvmTest/src/kotlinx/serialization/JavaCollectionsTest.kt
new file mode 100644
index 00000000..1f4958a6
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+++ b/formats/json-tests/jvmTest/src/kotlinx/serialization/JavaCollectionsTest.kt
@@ -0,0 +1,112 @@
+/*
+ * Copyright 2019 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package kotlinx.serialization
+
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.test.typeTokenOf
+import org.junit.Test
+import java.util.HashMap
+import java.util.HashSet
+import kotlin.collections.LinkedHashMap
+import kotlin.collections.Map
+import kotlin.collections.hashMapOf
+import kotlin.collections.hashSetOf
+import kotlin.reflect.*
+import kotlin.test.*
+
+
+class JavaCollectionsTest {
+    @Serializable
+    data class HasHashMap(
+        val s: String,
+        val hashMap: HashMap<Int, String>,
+        val hashSet: HashSet<Int>,
+        val linkedHashMap: LinkedHashMap<Int, String>,
+        val kEntry: Map.Entry<Int, String>?
+    )
+
+    @Test
+    fun testJavaCollectionsInsideClass() {
+        val original = HasHashMap("42", hashMapOf(1 to "1", 2 to "2"), hashSetOf(11), LinkedHashMap(), null)
+        val serializer = HasHashMap.serializer()
+        val string = Json.encodeToString(serializer = serializer, value = original)
+        assertEquals(
+            expected = """{"s":"42","hashMap":{"1":"1","2":"2"},"hashSet":[11],"linkedHashMap":{},"kEntry":null}""",
+            actual = string
+        )
+        val restored = Json.decodeFromString(deserializer = serializer, string = string)
+        assertEquals(expected = original, actual = restored)
+    }
+
+    @Test
+    fun testTopLevelMaps() {
+        // Returning null here is a deliberate choice: map constructor functions may return different specialized
+        // implementations (e.g., kotlin.collections.EmptyMap or java.util.Collections.SingletonMap)
+        // that may or may not be generic. Since we generally cannot return a generic serializer using Java class only,
+        // all attempts to get map serializer using only .javaClass should return null.
+        assertNull(serializerOrNull(emptyMap<String, String>().javaClass))
+        assertNull(serializerOrNull(mapOf<String, String>("a" to "b").javaClass))
+        assertNull(serializerOrNull(mapOf<String, String>("a" to "b", "b" to "c").javaClass))
+        // Correct ways of retrieving map serializer:
+        assertContains(
+            serializer(typeTokenOf<Map<String, String>>()).descriptor.serialName,
+            "kotlin.collections.LinkedHashMap"
+        )
+        assertContains(
+            serializer(typeTokenOf<java.util.LinkedHashMap<String, String>>()).descriptor.serialName,
+            "kotlin.collections.LinkedHashMap"
+        )
+        assertContains(
+            serializer(typeOf<LinkedHashMap<String, String>>()).descriptor.serialName,
+            "kotlin.collections.LinkedHashMap"
+        )
+    }
+
+    @Test
+    fun testTopLevelSetsAndLists() {
+        // Same reasoning as for maps
+        assertNull(serializerOrNull(emptyList<String>().javaClass))
+        assertNull(serializerOrNull(listOf<String>("a").javaClass))
+        assertNull(serializerOrNull(listOf<String>("a", "b").javaClass))
+        assertNull(serializerOrNull(emptySet<String>().javaClass))
+        assertNull(serializerOrNull(setOf<String>("a").javaClass))
+        assertNull(serializerOrNull(setOf<String>("a", "b").javaClass))
+        assertContains(
+            serializer(typeTokenOf<Set<String>>()).descriptor.serialName,
+            "kotlin.collections.LinkedHashSet"
+        )
+        assertContains(
+            serializer(typeTokenOf<List<String>>()).descriptor.serialName,
+            "kotlin.collections.ArrayList"
+        )
+        assertContains(
+            serializer(typeTokenOf<java.util.LinkedHashSet<String>>()).descriptor.serialName,
+            "kotlin.collections.LinkedHashSet"
+        )
+        assertContains(
+            serializer(typeTokenOf<java.util.ArrayList<String>>()).descriptor.serialName,
+            "kotlin.collections.ArrayList"
+        )
+    }
+
+    @Test
+    fun testAnonymousObject() {
+        val obj: Any = object {}
+        assertNull(serializerOrNull(obj.javaClass))
+    }
+}
+