No checking proto id duplication

Author: xiaozhikang0916

formats/protobuf/commonMain/src/kotlinx/serialization/protobuf/internal/ProtobufDecoding.kt

@@ -59,12 +59,6 @@ internal open class ProtobufDecoder(
                 }
             }
             indexCache = cache
-
-            // Class type should have unique proto id for its elements
-            require(descriptor.kind != StructureKind.CLASS ||
-                indexCache?.toSet()?.size == elements) {
-                "Duplicated proto number in ${descriptor.serialName}."
-            }
         } else {
             populateCacheMap(descriptor, elements)
         }
@@ -92,10 +86,7 @@ internal open class ProtobufDecoder(
     }
 
     private fun MutableMap<Int, Int>.putProtoId(protoId: Int, index: Int) {
-        val old = put(protoId, index)
-        require(old == null) {
-            "Duplicated proto number $protoId in ${descriptor.serialName} for elements: ${descriptor.getElementName(index)}, ${descriptor.getElementName(old!!)}."
-        }
+        put(protoId, index)
     }
 
     private fun getIndexByNum(protoNum: Int): Int {

formats/protobuf/commonTest/src/kotlinx/serialization/protobuf/ProtobufOneOfTest.kt

@@ -546,6 +546,7 @@ class ProtobufOneOfTest {
     @Test
     fun testDuplicatedIdClass() {
         val duplicated = DuplicatingIdData(DuplicatingIdStringType("foo"), 42)
+        // Fine to encode duplicated proto number properties in wire data
         ProtoBuf.encodeToHexString(duplicated).also {
             /**
              * 3:LEN {"foo"}
@@ -554,8 +555,11 @@ class ProtobufOneOfTest {
             assertEquals("1a03666f6f182a", it)
         }
 
+        // Without checking duplication of proto numbers,
+        // ProtoBuf just throw exception about wrong wire type
         assertFailsWithMessage<IllegalArgumentException>(
-            "Duplicated proto number 3 in kotlinx.serialization.protobuf.ProtobufOneOfTest.DuplicatingIdData for elements: d, bad."
+//            "Duplicated proto number 3 in kotlinx.serialization.protobuf.ProtobufOneOfTest.DuplicatingIdData for elements: d, bad."
+            "Expected wire type 0, but found 2"
         ) {
             /**
              * 3:LEN {"foo"}