Move converters from constraint violations into ValidationException…

… to decorators

This allows "easily" converting to other custom validation exception
shapes by implementing a decorator.

As a simple example, this PR adds a
`CustomValidationExceptionWithReasonDecorator` decorator that is able to
convert into a shape that is very similar to
`smithy.framework#ValidationException`, but that has an additional
`reason` field. The decorator can be enabled via the newly added
`experimentalCustomValidationExceptionWithReasonPleaseDoNotUse` codegen
config flag.

This effectively provides a way for users to use custom validation
exceptions without having to wait for the full implementation of #2053,
provided they're interested enough to write a decorator in a JVM
language. This mechanism is _experimental_ and will be removed once full
support for custom validation exceptions as described in #2053 lands,
hence why the configuration key is strongly worded in this respect.

This commit also ports the mechanism to run codegen integration tests
within Kotlin unit tests for client SDKs to the server. See #1956 for
details. The custom validation exception decorator is tested this way.

aws/sdk-codegen/src/test/kotlin/software/amazon/smithy/rustsdk/TestUtil.kt

@@ -13,6 +13,7 @@ import software.amazon.smithy.rust.codegen.client.testutil.testCodegenContext
 import software.amazon.smithy.rust.codegen.core.smithy.CoreRustSettings
 import software.amazon.smithy.rust.codegen.core.smithy.RuntimeCrateLocation
 import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
+import software.amazon.smithy.rust.codegen.core.testutil.IntegrationTestParams
 import software.amazon.smithy.rust.codegen.core.testutil.TestRuntimeConfig
 import software.amazon.smithy.rust.codegen.core.testutil.asSmithyModel
 import software.amazon.smithy.rust.codegen.core.testutil.testRustSettings
@@ -39,9 +40,10 @@ fun awsSdkIntegrationTest(
     test: (ClientCodegenContext, RustCrate) -> Unit = { _, _ -> },
 ) =
     clientIntegrationTest(
-        model, runtimeConfig = AwsTestRuntimeConfig,
-        additionalSettings = ObjectNode.builder()
-            .withMember(
+        model,
+        IntegrationTestParams(
+            runtimeConfig = AwsTestRuntimeConfig,
+            additionalSettings = ObjectNode.builder().withMember(
                 "customizationConfig",
                 ObjectNode.builder()
                     .withMember(
@@ -51,6 +53,7 @@ fun awsSdkIntegrationTest(
                             .build(),
                     ).build(),
             )
-            .withMember("codegen", ObjectNode.builder().withMember("includeFluentClient", false).build()).build(),
+                .withMember("codegen", ObjectNode.builder().withMember("includeFluentClient", false).build()).build(),
+        ),
         test = test,
     )

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/RustClientCodegenPlugin.kt

@@ -16,7 +16,7 @@ import software.amazon.smithy.rust.codegen.client.smithy.customize.NoOpEventStre
 import software.amazon.smithy.rust.codegen.client.smithy.customize.RequiredCustomizations
 import software.amazon.smithy.rust.codegen.client.smithy.endpoint.EndpointsDecorator
 import software.amazon.smithy.rust.codegen.client.smithy.generators.client.FluentClientDecorator
-import software.amazon.smithy.rust.codegen.client.testutil.DecoratableBuildPlugin
+import software.amazon.smithy.rust.codegen.client.testutil.ClientDecoratableBuildPlugin
 import software.amazon.smithy.rust.codegen.core.rustlang.Attribute.Companion.NonExhaustive
 import software.amazon.smithy.rust.codegen.core.rustlang.RustReservedWordSymbolProvider
 import software.amazon.smithy.rust.codegen.core.smithy.BaseSymbolMetadataProvider
@@ -36,7 +36,7 @@ import java.util.logging.Logger
  * `resources/META-INF.services/software.amazon.smithy.build.SmithyBuildPlugin` refers to this class by name which
  * enables the smithy-build plugin to invoke `execute` with all Smithy plugin context + models.
  */
-class RustClientCodegenPlugin : DecoratableBuildPlugin() {
+class RustClientCodegenPlugin : ClientDecoratableBuildPlugin() {
     override fun getName(): String = "rust-client-codegen"
 
     override fun executeWithDecorator(
@@ -66,10 +66,10 @@ class RustClientCodegenPlugin : DecoratableBuildPlugin() {
     }
 
     companion object {
-        /** SymbolProvider
+        /**
          * When generating code, smithy types need to be converted into Rust types—that is the core role of the symbol provider
          *
-         * The Symbol provider is composed of a base `SymbolVisitor` which handles the core functionality, then is layered
+         * The Symbol provider is composed of a base [SymbolVisitor] which handles the core functionality, then is layered
          * with other symbol providers, documented inline, to handle the full scope of Smithy types.
          */
         fun baseSymbolProvider(model: Model, serviceShape: ServiceShape, symbolVisitorConfig: SymbolVisitorConfig) =

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/testutil/ClientCodegenIntegrationTest.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.rust.codegen.client.testutil
+
+import software.amazon.smithy.build.PluginContext
+import software.amazon.smithy.build.SmithyBuildPlugin
+import software.amazon.smithy.model.Model
+import software.amazon.smithy.rust.codegen.client.smithy.ClientCodegenContext
+import software.amazon.smithy.rust.codegen.client.smithy.RustClientCodegenPlugin
+import software.amazon.smithy.rust.codegen.client.smithy.customize.ClientCodegenDecorator
+import software.amazon.smithy.rust.codegen.core.smithy.RustCrate
+import software.amazon.smithy.rust.codegen.core.testutil.IntegrationTestParams
+import software.amazon.smithy.rust.codegen.core.testutil.codegenIntegrationTest
+import java.nio.file.Path
+
+fun clientIntegrationTest(
+    model: Model,
+    params: IntegrationTestParams = IntegrationTestParams(),
+    additionalDecorators: List<ClientCodegenDecorator> = listOf(),
+    test: (ClientCodegenContext, RustCrate) -> Unit = { _, _ -> },
+): Path {
+    fun invokeRustCodegenPlugin(ctx: PluginContext) {
+        val codegenDecorator = object : ClientCodegenDecorator {
+            override val name: String = "Add tests"
+            override val order: Byte = 0
+
+            override fun classpathDiscoverable(): Boolean = false
+
+            override fun extras(codegenContext: ClientCodegenContext, rustCrate: RustCrate) {
+                test(codegenContext, rustCrate)
+            }
+        }
+        RustClientCodegenPlugin().executeWithDecorator(ctx, codegenDecorator, *additionalDecorators.toTypedArray())
+    }
+    return codegenIntegrationTest(model, params, invokePlugin = ::invokeRustCodegenPlugin)
+}
+
+/**
+ * A `SmithyBuildPlugin` that accepts an additional decorator.
+ *
+ * This exists to allow tests to easily customize the _real_ build without needing to list out customizations
+ * or attempt to manually discover them from the path.
+ */
+abstract class ClientDecoratableBuildPlugin : SmithyBuildPlugin {
+    abstract fun executeWithDecorator(
+        context: PluginContext,
+        vararg decorator: ClientCodegenDecorator,
+    )
+
+    override fun execute(context: PluginContext) {
+        executeWithDecorator(context)
+    }
+}

codegen-client/src/test/kotlin/software/amazon/smithy/rust/codegen/client/customizations/HttpVersionListGeneratorTest.kt

@@ -19,6 +19,7 @@ import software.amazon.smithy.rust.codegen.core.rustlang.rustTemplate
 import software.amazon.smithy.rust.codegen.core.rustlang.writable
 import software.amazon.smithy.rust.codegen.core.smithy.RuntimeConfig
 import software.amazon.smithy.rust.codegen.core.smithy.RuntimeType
+import software.amazon.smithy.rust.codegen.core.testutil.IntegrationTestParams
 import software.amazon.smithy.rust.codegen.core.testutil.asSmithyModel
 import software.amazon.smithy.rust.codegen.core.testutil.integrationTest
 
@@ -170,8 +171,8 @@ internal class HttpVersionListGeneratorTest {
 
         clientIntegrationTest(
             model,
-            listOf(FakeSigningDecorator()),
-            addModuleToEventStreamAllowList = true,
+            IntegrationTestParams(addModuleToEventStreamAllowList = true),
+            additionalDecorators = listOf(FakeSigningDecorator()),
         ) { clientCodegenContext, rustCrate ->
             val moduleName = clientCodegenContext.moduleUseName()
             rustCrate.integrationTest("validate_eventstream_http") {

codegen-client/src/test/kotlin/software/amazon/smithy/rust/codegen/client/endpoint/EndpointsDecoratorTest.kt

@@ -11,6 +11,7 @@ import org.junit.jupiter.api.Test
 import software.amazon.smithy.rust.codegen.client.testutil.clientIntegrationTest
 import software.amazon.smithy.rust.codegen.core.rustlang.Attribute
 import software.amazon.smithy.rust.codegen.core.rustlang.rust
+import software.amazon.smithy.rust.codegen.core.testutil.IntegrationTestParams
 import software.amazon.smithy.rust.codegen.core.testutil.asSmithyModel
 import software.amazon.smithy.rust.codegen.core.testutil.integrationTest
 import software.amazon.smithy.rust.codegen.core.testutil.runWithWarnings
@@ -123,8 +124,8 @@ class EndpointsDecoratorTest {
     fun `set an endpoint in the property bag`() {
         val testDir = clientIntegrationTest(
             model,
-            // just run integration tests
-            command = { "cargo test --test *".runWithWarnings(it) },
+            // Just run integration tests.
+            IntegrationTestParams(command = { "cargo test --test *".runWithWarnings(it) }),
         ) { clientCodegenContext, rustCrate ->
             rustCrate.integrationTest("endpoint_params_test") {
                 val moduleName = clientCodegenContext.moduleUseName()

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/rustlang/RustWriter.kt

@@ -481,7 +481,7 @@ class RustWriter private constructor(
      * Callers must take care to use [this] when writing to ensure code is written to the right place:
      * ```kotlin
      * val writer = RustWriter.forModule("model")
-     * writer.withModule(RustModule.public("nested")) {
+     * writer.withInlineModule(RustModule.public("nested")) {
      *   Generator(...).render(this) // GOOD
      *   Generator(...).render(writer) // WRONG!
      * }

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/testutil/CodegenIntegrationTest.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.rust.codegen.core.testutil
+
+import software.amazon.smithy.build.PluginContext
+import software.amazon.smithy.model.Model
+import software.amazon.smithy.model.node.ObjectNode
+import software.amazon.smithy.rust.codegen.core.smithy.RuntimeConfig
+import software.amazon.smithy.rust.codegen.core.util.runCommand
+import java.io.File
+import java.nio.file.Path
+
+/**
+ * A helper class holding common data with defaults that is threaded through several functions, to make their
+ * signatures shorter.
+ */
+data class IntegrationTestParams(
+    val addModuleToEventStreamAllowList: Boolean = false,
+    val service: String? = null,
+    val runtimeConfig: RuntimeConfig? = null,
+    val additionalSettings: ObjectNode = ObjectNode.builder().build(),
+    val overrideTestDir: File? = null,
+    val command: ((Path) -> Unit)? = null,
+)
+
+/**
+ * Run cargo test on a true, end-to-end, codegen product of a given model.
+ */
+fun codegenIntegrationTest(model: Model, params: IntegrationTestParams, invokePlugin: (PluginContext) -> Unit): Path {
+    val (ctx, testDir) = generatePluginContext(
+        model,
+        params.additionalSettings,
+        params.addModuleToEventStreamAllowList,
+        params.service,
+        params.runtimeConfig,
+        params.overrideTestDir,
+    )
+    invokePlugin(ctx)
+    ctx.fileManifest.printGeneratedFiles()
+    params.command?.invoke(testDir) ?: "cargo test".runCommand(testDir, environment = mapOf("RUSTFLAGS" to "-D warnings"))
+    return testDir
+}

codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/testutil/Rust.kt

@@ -190,8 +190,7 @@ fun generatePluginContext(
         )
     }
 
-    val settings = settingsBuilder.merge(additionalSettings)
-        .build()
+    val settings = settingsBuilder.merge(additionalSettings).build()
     val pluginContext = PluginContext.builder().model(model).fileManifest(manifest).settings(settings).build()
     return pluginContext to testPath
 }

codegen-server-test/build.gradle.kts

@@ -50,6 +50,12 @@ val allCodegenTests = "../codegen-core/common-test-models".let { commonModels ->
             imports = listOf("$commonModels/constraints.smithy"),
             extraConfig = """, "codegen": { "publicConstrainedTypes": false } """,
         ),
+        CodegenTest(
+            "com.amazonaws.constraints#CustomValidationExceptionsExperimental",
+            "custom_validation_exceptions_experimental",
+            imports = listOf("$commonModels/custom-validation-exceptions-experimental.smithy"),
+            extraConfig = """, "codegen": { "experimentalCustomValidationExceptionWithReasonPleaseDoNotUse": "com.amazonaws.constraints#ValidationException" } """.trimMargin(),
+        ),
         CodegenTest(
             "com.amazonaws.constraints#UniqueItemsService",
             "unique_items",

codegen-server/build.gradle.kts

@@ -26,6 +26,10 @@ dependencies {
     implementation(project(":codegen-core"))
     implementation("software.amazon.smithy:smithy-aws-traits:$smithyVersion")
     implementation("software.amazon.smithy:smithy-protocol-test-traits:$smithyVersion")
+
+    // `smithy.framework#ValidationException` is defined here, which is used in `constraints.smithy`, which is used
+    // in `CustomValidationExceptionWithReasonDecoratorTest`.
+    testImplementation("software.amazon.smithy:smithy-validation-model:$smithyVersion")
 }
 
 tasks.compileKotlin { kotlinOptions.jvmTarget = "1.8" }

codegen-server/python/src/main/kotlin/software/amazon/smithy/rust/codegen/server/python/smithy/PythonCodegenServerPlugin.kt

@@ -20,7 +20,9 @@ import software.amazon.smithy.rust.codegen.server.python.smithy.customizations.D
 import software.amazon.smithy.rust.codegen.server.smithy.ConstrainedShapeSymbolMetadataProvider
 import software.amazon.smithy.rust.codegen.server.smithy.ConstrainedShapeSymbolProvider
 import software.amazon.smithy.rust.codegen.server.smithy.DeriveEqAndHashSymbolMetadataProvider
+import software.amazon.smithy.rust.codegen.server.smithy.customizations.CustomValidationExceptionWithReasonDecorator
 import software.amazon.smithy.rust.codegen.server.smithy.customizations.ServerRequiredCustomizations
+import software.amazon.smithy.rust.codegen.server.smithy.customizations.SmithyValidationExceptionDecorator
 import software.amazon.smithy.rust.codegen.server.smithy.customize.CombinedServerCodegenDecorator
 import java.util.logging.Level
 import java.util.logging.Logger
@@ -47,7 +49,10 @@ class PythonCodegenServerPlugin : SmithyBuildPlugin {
         val codegenDecorator: CombinedServerCodegenDecorator =
             CombinedServerCodegenDecorator.fromClasspath(
                 context,
-                CombinedServerCodegenDecorator(DECORATORS + ServerRequiredCustomizations()),
+                ServerRequiredCustomizations(),
+                SmithyValidationExceptionDecorator(),
+                CustomValidationExceptionWithReasonDecorator(),
+                *DECORATORS,
             )
 
         // PythonServerCodegenVisitor is the main driver of code generation that traverses the model and generates code

codegen-server/python/src/main/kotlin/software/amazon/smithy/rust/codegen/server/python/smithy/PythonServerCodegenVisitor.kt

@@ -132,7 +132,7 @@ class PythonServerCodegenVisitor(
      */
     override fun stringShape(shape: StringShape) {
         fun pythonServerEnumGeneratorFactory(codegenContext: ServerCodegenContext, writer: RustWriter, shape: StringShape) =
-            PythonServerEnumGenerator(codegenContext, writer, shape)
+            PythonServerEnumGenerator(codegenContext, writer, shape, validationExceptionConversionGenerator)
         stringShape(shape, ::pythonServerEnumGeneratorFactory)
     }
 

codegen-server/python/src/main/kotlin/software/amazon/smithy/rust/codegen/server/python/smithy/customizations/PythonServerCodegenDecorator.kt

@@ -134,7 +134,7 @@ class PyO3ExtensionModuleDecorator : ServerCodegenDecorator {
     }
 }
 
-val DECORATORS = listOf(
+val DECORATORS = arrayOf(
     /**
      * Add the [InternalServerError] error to all operations.
      * This is done because the Python interpreter can raise exceptions during execution.