grpc-pb: Add oneOf message merge test

Signed-off-by: Johannes Zottele <[email protected]>

Author: Jozott00

grpc/grpc-core/src/commonTest/kotlin/kotlinx/rpc/grpc/pb/ProtosTest.kt

@@ -8,6 +8,8 @@ import OneOfMsg
 import OneOfMsgInternal
 import Outer
 import OuterInternal
+import asInternal
+import encodeWith
 import invoke
 import kotlinx.io.Buffer
 import kotlinx.rpc.grpc.codec.MessageCodec
@@ -177,6 +179,30 @@ class ProtosTest {
         }
     }
 
+    @Test
+    fun testOneOfMsgMerging() {
+        val part1 = OneOfMsg {
+            field = OneOfMsg.Field.Other(Other { arg2 = "arg2" })
+        }
+        val part2 = OneOfMsg {
+            field = OneOfMsg.Field.Other(Other { arg1 = "arg1" })
+        }
+
+        val buffer = Buffer()
+        val encoder = WireEncoder(buffer)
+        part1.asInternal().encodeWith(encoder)
+        part2.asInternal().encodeWith(encoder)
+        encoder.flush()
+
+
+        val decoded = OneOfMsgInternal.CODEC.decode(buffer)
+        assertIs<OneOfMsg.Field.Other>(decoded.field)
+        val decodedOther = (decoded.field as OneOfMsg.Field.Other).value
+        assertEquals("arg2", decodedOther.arg2)
+        assertEquals("arg1", decodedOther.arg1)
+        assertEquals(null, decodedOther.arg3)
+    }
+
     @Test
     fun testOneOfLastWins() {
         // write two values on the oneOf field.

protoc-gen/src/main/kotlin/kotlinx/rpc/protobuf/ModelToKotlinCommonGenerator.kt

@@ -265,7 +265,7 @@ class ModelToKotlinCommonGenerator(
             code("val tag = decoder.readTag() ?: break // EOF, we read the whole message")
             whenBlock {
                 declaration.fields().forEach { (_, field) -> readMatchCase(field) }
-                whenCase("else") { code("TODO(\"Handle unknown fields\")") }
+                whenCase("else") { code("TODO(\"Handle unknown fields: \$tag\")") }
             }
         }
         ifBranch(
@@ -394,7 +394,7 @@ class ModelToKotlinCommonGenerator(
 
             is FieldType.Message -> {
                 val internalClassName = fieldType.dec.value.internalClassFullName()
-                code("decoder.readMessage($lvalue.asInternal(), $internalClassName::decodeWith)")
+                code("decoder.readMessage($lvalue.asInternal(), $internalClassName.CODEC::decodeWith)")
             }
 
             is FieldType.Map -> TODO()