feat(codegen): generate client side error correction (#958)

.changes/d4722cf5-e6ef-4b42-b869-d854fd80be51.json

@@ -0,0 +1,5 @@
+{
+    "id": "d4722cf5-e6ef-4b42-b869-d854fd80be51",
+    "type": "feature",
+    "description": "Generate client side error correction for @required members"
+}

codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/core/RuntimeTypes.kt

@@ -349,7 +349,6 @@ object RuntimeTypes {
             val merge = "kotlinx.coroutines.flow.merge".toSymbol()
             val map = "kotlinx.coroutines.flow.map".toSymbol()
             val take = "kotlinx.coroutines.flow.take".toSymbol()
-            val drop = "kotlinx.coroutines.flow.drop".toSymbol()
             val single = "kotlinx.coroutines.flow.single".toSymbol()
         }
     }

codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/StructureGenerator.kt

@@ -9,16 +9,10 @@ import software.amazon.smithy.codegen.core.Symbol
 import software.amazon.smithy.kotlin.codegen.core.*
 import software.amazon.smithy.kotlin.codegen.lang.KotlinTypes
 import software.amazon.smithy.kotlin.codegen.model.*
+import software.amazon.smithy.kotlin.codegen.rendering.serde.ClientErrorCorrection
 import software.amazon.smithy.kotlin.codegen.utils.getOrNull
 import software.amazon.smithy.model.shapes.*
-import software.amazon.smithy.model.traits.ErrorTrait
-import software.amazon.smithy.model.traits.HttpLabelTrait
-import software.amazon.smithy.model.traits.HttpQueryParamsTrait
-import software.amazon.smithy.model.traits.HttpQueryTrait
-import software.amazon.smithy.model.traits.LengthTrait
-import software.amazon.smithy.model.traits.RetryableTrait
-import software.amazon.smithy.model.traits.SensitiveTrait
-import software.amazon.smithy.model.traits.StreamingTrait
+import software.amazon.smithy.model.traits.*
 
 /**
  * Renders Smithy structure shapes
@@ -285,6 +279,26 @@ class StructureGenerator(
                         .write("this.#L = #Q.invoke(block)", memberName, memberSymbol)
                         .closeBlock("}")
                 }
+
+                write("")
+
+                // render client side error correction function to set @required members to a default
+                withBlock(
+                    "internal fun correctErrors(): Builder {",
+                    "}",
+                ) {
+                    sortedMembers
+                        .filter(MemberShape::isRequired)
+                        .filterNot {
+                            val target = ctx.model.expectShape(it.target)
+                            target.isStreaming
+                        }
+                        .forEach {
+                            val correctedValue = ClientErrorCorrection.defaultValue(ctx, it, writer)
+                            write("if (#1L == null) #1L = #2L", ctx.symbolProvider.toMemberName(it), correctedValue)
+                        }
+                    write("return this")
+                }
             }
     }
 

codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/protocol/HttpBindingProtocolGenerator.kt

@@ -12,10 +12,7 @@ import software.amazon.smithy.kotlin.codegen.core.*
 import software.amazon.smithy.kotlin.codegen.lang.KotlinTypes
 import software.amazon.smithy.kotlin.codegen.lang.toEscapedLiteral
 import software.amazon.smithy.kotlin.codegen.model.*
-import software.amazon.smithy.kotlin.codegen.rendering.serde.deserializerName
-import software.amazon.smithy.kotlin.codegen.rendering.serde.formatInstant
-import software.amazon.smithy.kotlin.codegen.rendering.serde.parseInstant
-import software.amazon.smithy.kotlin.codegen.rendering.serde.serializerName
+import software.amazon.smithy.kotlin.codegen.rendering.serde.*
 import software.amazon.smithy.model.Model
 import software.amazon.smithy.model.knowledge.HttpBinding
 import software.amazon.smithy.model.shapes.*
@@ -573,7 +570,6 @@ abstract class HttpBindingProtocolGenerator : ProtocolGenerator {
         writer: KotlinWriter,
     ) {
         writer
-            .addImport(RuntimeTypes.Core.ExecutionContext)
             .openBlock(
                 "override suspend fun deserialize(context: #T, call: #T): #T {",
                 RuntimeTypes.Core.ExecutionContext,
@@ -618,6 +614,10 @@ abstract class HttpBindingProtocolGenerator : ProtocolGenerator {
                         renderDeserializeResponseCode(ctx, it, writer)
                     }
             }
+            // Render client side error correction for `@required` members.
+            // NOTE: nested members bound via the document/payload will be handled by the deserializer for the relevant
+            // content type. All other members (e.g. bound via REST semantics) will be corrected here.
+            .write("builder.correctErrors()")
             .write("return builder.build()")
             .closeBlock("}")
     }

codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/ClientErrorCorrection.kt

@@ -0,0 +1,63 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package software.amazon.smithy.kotlin.codegen.rendering.serde
+
+import software.amazon.smithy.codegen.core.CodegenException
+import software.amazon.smithy.kotlin.codegen.core.CodegenContext
+import software.amazon.smithy.kotlin.codegen.core.KotlinWriter
+import software.amazon.smithy.kotlin.codegen.core.RuntimeTypes
+import software.amazon.smithy.kotlin.codegen.model.isEnum
+import software.amazon.smithy.model.shapes.MemberShape
+import software.amazon.smithy.model.shapes.ShapeType
+
+object ClientErrorCorrection {
+    /**
+     * Determine the default value for a required member based on
+     * [client error correction](https://smithy.io/2.0/spec/aggregate-types.html?highlight=error%20correction#client-error-correction)
+     *
+     * @param ctx the generation context
+     * @param member the target member shape to get the default value for
+     * @param writer the writer the default value will be written to, this is used for certain shapes to format the
+     * default value which will mutate the writer (e.g. add imports).
+     * @return default value expression as a string
+     */
+    fun defaultValue(
+        ctx: CodegenContext,
+        member: MemberShape,
+        writer: KotlinWriter,
+    ): String {
+        val target = ctx.model.expectShape(member.target)
+        val targetSymbol = ctx.symbolProvider.toSymbol(target)
+
+        // In IDL v1 all enums were `ShapeType.STRING` and you had to explicitly check for the @enum trait, this handles
+        // the differences in IDL versions
+        if (target.isEnum) {
+            return writer.format("#T.SdkUnknown(#S)", targetSymbol, "no value provided")
+        }
+
+        return when (target.type) {
+            ShapeType.BLOB -> "ByteArray(0)"
+            ShapeType.BOOLEAN -> "false"
+            ShapeType.STRING -> "\"\""
+            ShapeType.BYTE -> "0.toByte()"
+            ShapeType.SHORT -> "0.toShort()"
+            ShapeType.INTEGER -> "0"
+            ShapeType.LONG -> "0L"
+            ShapeType.FLOAT -> "0f"
+            ShapeType.DOUBLE -> "0.0"
+            ShapeType.BIG_INTEGER -> writer.format("#T(\"0\")", RuntimeTypes.Core.Content.BigInteger)
+            ShapeType.BIG_DECIMAL -> writer.format("#T(\"0\")", RuntimeTypes.Core.Content.BigDecimal)
+            ShapeType.DOCUMENT -> "null"
+            ShapeType.UNION -> writer.format("#T.SdkUnknown", targetSymbol)
+            ShapeType.LIST,
+            ShapeType.SET,
+            -> "emptyList()"
+            ShapeType.MAP -> "emptyMap()"
+            ShapeType.STRUCTURE -> writer.format("#T.Builder().correctErrors().build()", targetSymbol)
+            ShapeType.TIMESTAMP -> writer.format("#T.fromEpochSeconds(0)", RuntimeTypes.Core.Instant)
+            else -> throw CodegenException("unexpected member type $member")
+        }
+    }
+}

codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/JsonParserGenerator.kt

@@ -98,6 +98,7 @@ open class JsonParserGenerator(
                         else -> {
                             writer.write("val builder = #T.Builder()", symbol)
                             renderDeserializerBody(ctx, shape, members.toList(), writer)
+                            writer.write("builder.correctErrors()")
                             writer.write("return builder.build()")
                         }
                     }

codegen/smithy-kotlin-codegen/src/main/kotlin/software/amazon/smithy/kotlin/codegen/rendering/serde/XmlParserGenerator.kt

@@ -109,6 +109,7 @@ open class XmlParserGenerator(
                     } else {
                         writer.write("val builder = #T.Builder()", symbol)
                         renderDeserializerBody(ctx, shape, members.toList(), writer)
+                        writer.write("builder.correctErrors()")
                         writer.write("return builder.build()")
                     }
                 }

codegen/smithy-kotlin-codegen/src/test/kotlin/software/amazon/smithy/kotlin/codegen/rendering/EnumGeneratorTest.kt

@@ -12,14 +12,16 @@ import software.amazon.smithy.kotlin.codegen.core.KotlinWriter
 import software.amazon.smithy.kotlin.codegen.model.expectShape
 import software.amazon.smithy.kotlin.codegen.test.*
 import software.amazon.smithy.model.shapes.IntEnumShape
+import software.amazon.smithy.model.shapes.ShapeType
 import software.amazon.smithy.model.shapes.StringShape
 import kotlin.test.Test
+import kotlin.test.assertEquals
 import kotlin.test.assertFailsWith
 
 class EnumGeneratorTest {
 
     @Test
-    fun `it generates unnamed string enums`() {
+    fun itGeneratesUnnamedStringEnumsIdlv1() {
         val model = """
             @enum([
                 {
@@ -33,10 +35,35 @@ class EnumGeneratorTest {
             @documentation("Documentation for this enum")
             string Baz
             
-        """.prependNamespaceAndService(namespace = "test").toSmithyModel()
+        """
+        testUnnamedStringEnum(model, "1.0")
+    }
+
+    @Test
+    fun itGeneratesUnnamedStringEnumsIdlv2() {
+        val model = """
+            @documentation("Documentation for this enum")
+            enum Baz {
+                FOO,
+                
+                @documentation("Documentation for bar")
+                BAR,
+            }
+        """
+        testUnnamedStringEnum(model, "2.0")
+    }
+
+    private fun testUnnamedStringEnum(modelContents: String, idlVersion: String) {
+        val model = modelContents.prependNamespaceAndService(version = idlVersion, namespace = "test").toSmithyModel()
 
         val provider = KotlinCodegenPlugin.createSymbolProvider(model, rootNamespace = "test")
         val shape = model.expectShape<StringShape>("test#Baz")
+        val expectedShapeType = when (idlVersion) {
+            "1.0" -> ShapeType.STRING
+            else -> ShapeType.ENUM
+        }
+        assertEquals(expectedShapeType, shape.type)
+
         val symbol = provider.toSymbol(shape)
         val writer = KotlinWriter(TestModelDefault.NAMESPACE)
         EnumGenerator(shape, symbol, writer).render()

codegen/smithy-kotlin-codegen/src/test/kotlin/software/amazon/smithy/kotlin/codegen/rendering/StructureGeneratorTest.kt

@@ -197,6 +197,10 @@ class StructureGeneratorTest {
                 public fun quux(block: com.test.model.Qux.Builder.() -> kotlin.Unit) {
                     this.quux = com.test.model.Qux.invoke(block)
                 }
+                
+                internal fun correctErrors(): Builder {
+                    return this
+                }
             }
         """.formatForTest()
         commonTestContents.shouldContainOnlyOnceWithDiff(expected)

codegen/smithy-kotlin-codegen/src/test/kotlin/software/amazon/smithy/kotlin/codegen/rendering/protocol/HttpBindingProtocolGeneratorTest.kt

@@ -17,13 +17,6 @@ import kotlin.test.assertTrue
 // NOTE: protocol conformance is mostly handled by the protocol tests suite
 class HttpBindingProtocolGeneratorTest {
     private val defaultModel = loadModelFromResource("http-binding-protocol-generator-test.smithy")
-    private val modelPrefix = """
-            @http(method: "POST", uri: "/foo-no-input")
-            operation Foo {
-                input: FooRequest
-            }        
-    """.prependNamespaceAndService(protocol = AwsProtocolModelDeclaration.REST_JSON, operations = listOf("Foo")).trimIndent()
-
     private fun getTransformFileContents(filename: String, testModel: Model = defaultModel): String {
         val (ctx, manifest, generator) = testModel.newTestContext()
         generator.generateProtocolClient(ctx)
@@ -380,6 +373,7 @@ internal class SmokeTestOperationDeserializer: HttpDeserialize<SmokeTestResponse
         if (payload != null) {
             deserializeSmokeTestOperationBody(builder, payload)
         }
+        builder.correctErrors()
         return builder.build()
     }
 }
@@ -433,6 +427,17 @@ internal class SmokeTestOperationDeserializer: HttpDeserialize<SmokeTestResponse
         contents.shouldContainOnlyOnce(expectedContents)
     }
 
+    @Test
+    fun itDeserializesExplicitEnumPayloads() {
+        val contents = getTransformFileContents("ExplicitEnumOperationDeserializer.kt")
+        contents.assertBalancedBracesAndParens()
+        val expectedContents = """
+        val contents = response.body.readAll()?.decodeToString()
+        builder.payload1 = contents?.let { MyEnum.fromValue(it) }
+"""
+        contents.shouldContainOnlyOnce(expectedContents)
+    }
+
     @Test
     fun itDeserializesExplicitBlobPayloads() {
         val contents = getTransformFileContents("ExplicitBlobOperationDeserializer.kt")

codegen/smithy-kotlin-codegen/src/test/resources/software/amazon/smithy/kotlin/codegen/http-binding-protocol-generator-test.smithy

@@ -10,6 +10,7 @@ service Test {
         SmokeTest,
         DuplicateInputTest,
         ExplicitString,
+        ExplicitEnum,
         ExplicitBlob,
         ExplicitBlobStream,
         ExplicitStruct,
@@ -112,6 +113,22 @@ structure ExplicitStringResponse {
     payload1: String
 }
 
+@http(method: "POST", uri: "/explicit/enum")
+operation ExplicitEnum {
+    input: ExplicitEnumRequest,
+    output: ExplicitEnumResponse
+}
+
+structure ExplicitEnumRequest {
+    @httpPayload
+    payload1: MyEnum
+}
+
+structure ExplicitEnumResponse {
+    @httpPayload
+    payload1: MyEnum
+}
+
 @http(method: "POST", uri: "/explicit/blob")
 operation ExplicitBlob {
     input: ExplicitBlobRequest,