fix: correctly deserialize restjson error code (#865)

* fix: correctly deserialize restjson error code (#828)

* Fixed change log format and restjson error code deserialization

* Fixed bug and added unit tests

* Added extra unit test

* Removed redundant code

* Simplified code/Removed duplicate lines

Author: 0marperez

.changes/c641c1f7-0758-49d2-8dbd-e375853143c7.json

@@ -0,0 +1,8 @@
+{
+    "id": "c641c1f7-0758-49d2-8dbd-e375853143c7",
+    "type": "bugfix",
+    "description": "Use correct precedence order for determining restJson error codes",
+    "issues": [
+        "awslabs/smithy-kotlin#828"
+    ]
+}

runtime/protocol/aws-json-protocols/common/src/aws/smithy/kotlin/runtime/awsprotocol/json/RestJsonErrorDeserializer.kt

@@ -46,20 +46,17 @@ public object RestJsonErrorDeserializer {
     }
 
     public fun deserialize(headers: Headers, payload: ByteArray?): ErrorDetails {
-        var code: String? = headers[X_AMZN_ERROR_TYPE_HEADER_NAME]
-        var message: String? = headers[X_AMZN_ERROR_MESSAGE_HEADER_NAME]
-        if (message == null) {
-            message = headers[X_AMZN_EVENT_ERROR_MESSAGE_HEADER_NAME]
-        }
+        var message = headers[X_AMZN_ERROR_MESSAGE_HEADER_NAME] ?: headers[X_AMZN_EVENT_ERROR_MESSAGE_HEADER_NAME]
+        val headerCode: String? = headers[X_AMZN_ERROR_TYPE_HEADER_NAME]
+        var bodyCode: String? = null
+        var bodyType: String? = null
 
         if (payload != null) {
-            val deserializer = JsonDeserializer(payload)
-            deserializer.deserializeStruct(OBJ_DESCRIPTOR) {
-                loop@while (true) {
+            JsonDeserializer(payload).deserializeStruct(OBJ_DESCRIPTOR) {
+                loop@ while (true) {
                     when (findNextFieldIndex()) {
-                        ERR_CODE_ALT1_DESCRIPTOR.index,
-                        ERR_CODE_ALT2_DESCRIPTOR.index,
-                        -> code = deserializeString()
+                        ERR_CODE_ALT1_DESCRIPTOR.index -> bodyCode = deserializeString()
+                        ERR_CODE_ALT2_DESCRIPTOR.index -> bodyType = deserializeString()
                         MESSAGE_ALT1_DESCRIPTOR.index,
                         MESSAGE_ALT2_DESCRIPTOR.index,
                         MESSAGE_ALT3_DESCRIPTOR.index,
@@ -70,8 +67,16 @@ public object RestJsonErrorDeserializer {
                 }
             }
         }
-
-        return ErrorDetails(sanitize(code), message, requestId = null)
+        /**
+         * According to the spec we should check the following locations in order:
+         *
+         * HTTP header x-amzn-errortype
+         * top-level body field code
+         * top-level body field __type
+         *
+         * Source: https://github.com/awslabs/aws-sdk-kotlin/issues/828
+         */
+        return ErrorDetails(sanitize(headerCode ?: bodyCode ?: bodyType), message, requestId = null)
     }
 }
 

runtime/protocol/aws-json-protocols/common/test/aws/smithy/kotlin/runtime/awsprotocol/json/RestJsonErrorDeserializerTest.kt

@@ -64,6 +64,54 @@ class RestJsonErrorDeserializerTest {
         }
     }
 
+    @OptIn(ExperimentalStdlibApi::class, ExperimentalCoroutinesApi::class)
+    @Test
+    fun `it deserializes aws restJson error codes using right location check order`() = runTest {
+        // Checking for header code return
+        var headers = Headers {
+            append(X_AMZN_ERROR_TYPE_HEADER_NAME, "HeaderCode")
+        }
+        var payload = """
+            {
+                "code": "BodyCode",
+                "__type": "TypeCode"
+            }
+        """.trimIndent().encodeToByteArray()
+        assertEquals("HeaderCode", RestJsonErrorDeserializer.deserialize(headers, payload).code)
+
+        payload = """
+            {
+                "__type": "TypeCode"
+            }
+        """.trimIndent().encodeToByteArray()
+        assertEquals("HeaderCode", RestJsonErrorDeserializer.deserialize(headers, payload).code)
+
+        payload = """
+            {
+                "code": "BodyCode"
+            }
+        """.trimIndent().encodeToByteArray()
+        assertEquals("HeaderCode", RestJsonErrorDeserializer.deserialize(headers, payload).code)
+
+        // Checking for body code return
+        headers = Headers {}
+        payload = """
+            {
+                "code": "BodyCode",
+                "__type": "TypeCode"
+            }
+        """.trimIndent().encodeToByteArray()
+        assertEquals("BodyCode", RestJsonErrorDeserializer.deserialize(headers, payload).code)
+
+        payload = """
+            {
+                "__type": "TypeCode",
+                "code": "BodyCode"
+            }
+        """.trimIndent().encodeToByteArray()
+        assertEquals("BodyCode", RestJsonErrorDeserializer.deserialize(headers, payload).code)
+    }
+
     @OptIn(ExperimentalStdlibApi::class, ExperimentalCoroutinesApi::class)
     @Test
     fun `it deserializes aws restJson error messages`() = runTest {