fix: handle upper/lowercase message field in error structs (#163)

Author: ianbotsf

codegen/smithy-aws-kotlin-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/protocols/RestXml.kt

@@ -7,6 +7,7 @@ package aws.sdk.kotlin.codegen.protocols
 
 import aws.sdk.kotlin.codegen.protocols.core.AwsHttpBindingProtocolGenerator
 import aws.sdk.kotlin.codegen.protocols.xml.RestXmlErrorMiddleware
+import aws.sdk.kotlin.codegen.protocols.xml.RestXmlSerdeDescriptorGenerator
 import software.amazon.smithy.aws.traits.protocols.RestXmlTrait
 import software.amazon.smithy.kotlin.codegen.core.*
 import software.amazon.smithy.kotlin.codegen.model.*
@@ -51,7 +52,7 @@ class RestXml : AwsHttpBindingProtocolGenerator() {
         val sortedMembers = sortMembersForSerialization(members)
 
         // render the serde descriptors
-        XmlSerdeDescriptorGenerator(ctx.toRenderingContext(this, shape, writer), sortedMembers).render()
+        RestXmlSerdeDescriptorGenerator(ctx.toRenderingContext(this, shape, writer), sortedMembers).render()
         if (shape.isUnionShape) {
             SerializeUnionGenerator(ctx, sortedMembers, writer, defaultTimestampFormat).render()
         } else {
@@ -115,7 +116,7 @@ class RestXml : AwsHttpBindingProtocolGenerator() {
         members: List<MemberShape>,
         writer: KotlinWriter,
     ) {
-        XmlSerdeDescriptorGenerator(ctx.toRenderingContext(this, shape, writer), members).render()
+        RestXmlSerdeDescriptorGenerator(ctx.toRenderingContext(this, shape, writer), members).render()
         if (shape.isUnionShape) {
             val name = ctx.symbolProvider.toSymbol(shape).name
             DeserializeUnionGenerator(ctx, name, members, writer, defaultTimestampFormat).render()

codegen/smithy-aws-kotlin-codegen/src/main/kotlin/aws/sdk/kotlin/codegen/protocols/xml/RestXmlSerdeDescriptorGenerator.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+package aws.sdk.kotlin.codegen.protocols.xml
+
+import software.amazon.smithy.kotlin.codegen.core.RenderingContext
+import software.amazon.smithy.kotlin.codegen.core.RuntimeTypes
+import software.amazon.smithy.kotlin.codegen.model.isError
+import software.amazon.smithy.kotlin.codegen.rendering.serde.SdkFieldDescriptorTrait
+import software.amazon.smithy.kotlin.codegen.rendering.serde.XmlSerdeDescriptorGenerator
+import software.amazon.smithy.kotlin.codegen.rendering.serde.add
+import software.amazon.smithy.kotlin.codegen.utils.dq
+import software.amazon.smithy.kotlin.codegen.utils.toggleFirstCharacterCase
+import software.amazon.smithy.model.shapes.MemberShape
+import software.amazon.smithy.model.shapes.Shape
+
+/**
+ * restXml-specific descriptor generator
+ */
+class RestXmlSerdeDescriptorGenerator(
+    ctx: RenderingContext<Shape>,
+    memberShapes: List<MemberShape>? = null
+) : XmlSerdeDescriptorGenerator(ctx, memberShapes) {
+    override fun getFieldDescriptorTraits(
+        member: MemberShape,
+        targetShape: Shape,
+        nameSuffix: String
+    ): List<SdkFieldDescriptorTrait> {
+        val traitList = super.getFieldDescriptorTraits(member, targetShape, nameSuffix).toMutableList()
+
+        if (ctx.shape?.isError == true) {
+            val serialName = getSerialName(member, nameSuffix)
+            if (serialName.equals("message", ignoreCase = true)) {
+                // Need to be able to read error messages from "Message" or "message"
+                // https://github.com/awslabs/smithy-kotlin/issues/352
+                traitList.add(RuntimeTypes.Serde.SerdeXml.XmlAliasName, serialName.toggleFirstCharacterCase().dq())
+            }
+        }
+
+        return traitList
+    }
+}

codegen/smithy-aws-kotlin-codegen/src/test/kotlin/aws/sdk/kotlin/codegen/protocols/xml/RestXmlSerdeDescriptorGeneratorTest.kt

@@ -0,0 +1,61 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+package aws.sdk.kotlin.codegen.protocols.xml
+
+import org.junit.jupiter.api.Test
+import software.amazon.smithy.kotlin.codegen.test.*
+import software.amazon.smithy.model.shapes.ShapeId
+
+class RestXmlSerdeDescriptorGeneratorTest {
+    private fun render(modelSnippet: String): String {
+        val model = modelSnippet.prependNamespaceAndService().toSmithyModel()
+
+        val testCtx = model.newTestContext()
+        val writer = testCtx.newWriter()
+        val shape = model.expectShape(ShapeId.from("com.test#Foo"))
+        val renderingCtx = testCtx.toRenderingContext(writer, shape)
+
+        RestXmlSerdeDescriptorGenerator(renderingCtx).render()
+        return writer.toString()
+    }
+
+    @Test
+    fun `it should add alias for message field in error struct`() {
+        val generated = render(
+            """
+                @error("client")
+                structure Foo { 
+                    message: String,
+                    foo: String
+                }
+            """.trimIndent()
+        )
+
+        val expectedDescriptors = """
+            val FOO_DESCRIPTOR = SdkFieldDescriptor(SerialKind.String, XmlSerialName("foo"))
+            val MESSAGE_DESCRIPTOR = SdkFieldDescriptor(SerialKind.String, XmlSerialName("message"), XmlAliasName("Message"))
+        """.formatForTest("")
+
+        generated.shouldContainOnlyOnceWithDiff(expectedDescriptors)
+    }
+
+    @Test
+    fun `it should not add alias for message field in non-error struct`() {
+        val generated = render(
+            """
+                structure Foo { 
+                    message: String
+                }
+            """.trimIndent()
+        )
+
+        val expectedDescriptors = """
+            val MESSAGE_DESCRIPTOR = SdkFieldDescriptor(SerialKind.String, XmlSerialName("message"))
+        """.formatForTest("")
+
+        generated.shouldContainOnlyOnceWithDiff(expectedDescriptors)
+    }
+}