1 files changed, 128 insertions, 0 deletions
diff --git a/formats/json-tests/commonTest/src/kotlinx/serialization/json/TrailingCommaTest.kt b/formats/json-tests/commonTest/src/kotlinx/serialization/json/TrailingCommaTest.kt
new file mode 100644
index 00000000..0916de57
--- /dev/null
+++ b/formats/json-tests/commonTest/src/kotlinx/serialization/json/TrailingCommaTest.kt
@@ -0,0 +1,128 @@
+/*
+ * Copyright 2017-2023 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package kotlinx.serialization.json
+
+import kotlinx.serialization.*
+import kotlinx.serialization.test.*
+import kotlin.test.*
+
+class TrailingCommaTest : JsonTestBase() {
+    val tj = Json { allowTrailingComma = true }
+
+    @Serializable
+    data class Optional(val data: String = "")
+
+    @Serializable
+    data class MultipleFields(val a: String, val b: String, val c: String)
+
+    private val multipleFields = MultipleFields("1", "2", "3")
+
+    @Serializable
+    data class WithMap(val m: Map<String, String>)
+
+    private val withMap = WithMap(mapOf("a" to "1", "b" to "2", "c" to "3"))
+
+    @Serializable
+    data class WithList(val l: List<Int>)
+
+    private val withList = WithList(listOf(1, 2, 3))
+
+    @Test
+    fun basic() = parametrizedTest { mode ->
+        val sd = """{"data":"str",}"""
+        assertEquals(Optional("str"), tj.decodeFromString<Optional>(sd, mode))
+    }
+
+    @Test
+    fun trailingCommaNotAllowedByDefaultForObjects() = parametrizedTest { mode ->
+        val sd = """{"data":"str",}"""
+        checkSerializationException({
+            default.decodeFromString<Optional>(sd, mode)
+        }, { message ->
+            assertContains(
+                message,
+                """Unexpected JSON token at offset 13: Trailing comma before the end of JSON object"""
+            )
+        })
+    }
+
+    @Test
+    fun trailingCommaNotAllowedByDefaultForLists() = parametrizedTest { mode ->
+        val sd = """{"l":[1,]}"""
+        checkSerializationException({
+            default.decodeFromString<WithList>(sd, mode)
+        }, { message ->
+            assertContains(
+                message,
+                """Unexpected JSON token at offset 7: Trailing comma before the end of JSON array"""
+            )
+        })
+    }
+
+    @Test
+    fun trailingCommaNotAllowedByDefaultForMaps() = parametrizedTest { mode ->
+        val sd = """{"m":{"a": "b",}}"""
+        checkSerializationException({
+            default.decodeFromString<WithMap>(sd, mode)
+        }, { message ->
+            assertContains(
+                message,
+                """Unexpected JSON token at offset 14: Trailing comma before the end of JSON object"""
+            )
+        })
+    }
+
+    @Test
+    fun emptyObjectNotAllowed() = parametrizedTest { mode ->
+        assertFailsWithMessage<SerializationException>("Unexpected leading comma") {
+            tj.decodeFromString<Optional>("""{,}""", mode)
+        }
+    }
+
+    @Test
+    fun emptyListNotAllowed() = parametrizedTest { mode ->
+        assertFailsWithMessage<SerializationException>("Unexpected leading comma") {
+            tj.decodeFromString<WithList>("""{"l":[,]}""", mode)
+        }
+    }
+
+    @Test
+    fun emptyMapNotAllowed() = parametrizedTest { mode ->
+        assertFailsWithMessage<SerializationException>("Unexpected leading comma") {
+            tj.decodeFromString<WithMap>("""{"m":{,}}""", mode)
+        }
+    }
+
+    @Test
+    fun testMultipleFields() = parametrizedTest { mode ->
+        val input = """{"a":"1","b":"2","c":"3", }"""
+        assertEquals(multipleFields, tj.decodeFromString(input, mode))
+    }
+
+    @Test
+    fun testWithMap() = parametrizedTest { mode ->
+        val input = """{"m":{"a":"1","b":"2","c":"3", }}"""
+
+        assertEquals(withMap, tj.decodeFromString(input, mode))
+    }
+
+    @Test
+    fun testWithList() = parametrizedTest { mode ->
+        val input = """{"l":[1, 2, 3, ]}"""
+        assertEquals(withList, tj.decodeFromString(input, mode))
+    }
+
+    @Serializable
+    data class Mixed(val mf: MultipleFields, val wm: WithMap, val wl: WithList)
+
+    @Test
+    fun testMixed() = parametrizedTest { mode ->
+        //language=JSON5
+        val input = """{"mf":{"a":"1","b":"2","c":"3",},
+            "wm":{"m":{"a":"1","b":"2","c":"3",},},
+            "wl":{"l":[1, 2, 3,],},}"""
+        assertEquals(Mixed(multipleFields, withMap, withList), tj.decodeFromString(input, mode))
+    }
+}