Make SdkError::into_service_error infallible (#1974)

smithy-lang · Nov 16, 2022 · 9f0bc36 · 9f0bc36
1 parent 4563849
commit 9f0bc36
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Showing 4 changed files with 60 additions and 29 deletions.
diff --git a/...oftware/amazon/smithy/rust/codegen/core/smithy/generators/error/CombinedErrorGenerator.kt b/...oftware/amazon/smithy/rust/codegen/core/smithy/generators/error/CombinedErrorGenerator.kt
@@ -13,11 +13,13 @@ import software.amazon.smithy.model.shapes.StructureShape
 import software.amazon.smithy.model.shapes.UnionShape
 import software.amazon.smithy.model.traits.RetryableTrait
 import software.amazon.smithy.rust.codegen.core.rustlang.Attribute
+import software.amazon.smithy.rust.codegen.core.rustlang.CargoDependency
 import software.amazon.smithy.rust.codegen.core.rustlang.RustMetadata
 import software.amazon.smithy.rust.codegen.core.rustlang.RustModule
 import software.amazon.smithy.rust.codegen.core.rustlang.RustWriter
 import software.amazon.smithy.rust.codegen.core.rustlang.Visibility
 import software.amazon.smithy.rust.codegen.core.rustlang.Writable
+import software.amazon.smithy.rust.codegen.core.rustlang.asType
 import software.amazon.smithy.rust.codegen.core.rustlang.deprecatedShape
 import software.amazon.smithy.rust.codegen.core.rustlang.documentShape
 import software.amazon.smithy.rust.codegen.core.rustlang.rust
@@ -124,6 +126,7 @@ class CombinedErrorGenerator(
 ) {
     private val runtimeConfig = symbolProvider.config().runtimeConfig
     private val genericError = RuntimeType.GenericError(symbolProvider.config().runtimeConfig)
+    private val createUnhandledError = CargoDependency.SmithyHttp(runtimeConfig).asType().member("result::CreateUnhandledError")
 
     fun render(writer: RustWriter) {
         val errorSymbol = RuntimeType("${operationSymbol.name}Error", null, "crate::error")
@@ -154,6 +157,15 @@ class CombinedErrorGenerator(
                 RuntimeType.GenericError(runtimeConfig),
             )
         }
+        writer.rustBlock("impl #T for ${errorSymbol.name}", createUnhandledError) {
+            rustBlock("fn create_unhandled_error(source: Box<dyn std::error::Error + Send + Sync + 'static>) -> Self") {
+                rustBlock("Self") {
+                    rust("kind: ${errorSymbol.name}Kind::Unhandled(#T::new(source)),", unhandledError())
+                    rust("meta: Default::default()")
+                }
+            }
+        }
+
         writer.rust("/// Types of errors that can occur for the `${operationSymbol.name}` operation.")
         meta.render(writer)
         writer.rustBlock("enum ${errorSymbol.name}Kind") {

diff --git a/...oftware/amazon/smithy/rust/codegen/core/smithy/generators/error/TopLevelErrorGenerator.kt b/...oftware/amazon/smithy/rust/codegen/core/smithy/generators/error/TopLevelErrorGenerator.kt
@@ -95,6 +95,7 @@ class TopLevelErrorGenerator(private val codegenContext: CodegenContext, private
 
     private fun RustWriter.renderImplFrom(errorSymbol: RuntimeType, errors: List<ShapeId>) {
         if (errors.isNotEmpty() || CodegenTarget.CLIENT == codegenContext.target) {
+            val operationErrors = errors.map { model.expectShape(it) }
             rustBlock(
                 "impl<R> From<#T<#T, R>> for Error where R: Send + Sync + std::fmt::Debug + 'static",
                 sdkError,
@@ -106,22 +107,27 @@ class TopLevelErrorGenerator(private val codegenContext: CodegenContext, private
                     "OpError" to errorSymbol,
                 ) {
                     rustBlock("match err") {
-                        val operationErrors = errors.map { model.expectShape(it) }
-                        rustBlock("#T::ServiceError(context) => match context.into_err().kind", sdkError) {
-                            operationErrors.forEach { errorShape ->
-                                val errSymbol = symbolProvider.toSymbol(errorShape)
-                                rust(
-                                    "#TKind::${errSymbol.name}(inner) => Error::${errSymbol.name}(inner),",
-                                    errorSymbol,
-                                )
-                            }
-                            rustTemplate(
-                                "#{errorSymbol}Kind::Unhandled(inner) => Error::Unhandled(#{unhandled}::new(inner.into())),",
-                                "errorSymbol" to errorSymbol,
-                                "unhandled" to unhandledError(),
+                        rust("#T::ServiceError(context) => Self::from(context.into_err()),", sdkError)
+                        rust("_ => Error::Unhandled(#T::new(err.into())),", unhandledError())
+                    }
+                }
+            }
+
+            rustBlock("impl From<#T> for Error", errorSymbol) {
+                rustBlock("fn from(err: #T) -> Self", errorSymbol) {
+                    rustBlock("match err.kind") {
+                        operationErrors.forEach { errorShape ->
+                            val errSymbol = symbolProvider.toSymbol(errorShape)
+                            rust(
+                                "#TKind::${errSymbol.name}(inner) => Error::${errSymbol.name}(inner),",
+                                errorSymbol,
                             )
                         }
-                        rust("_ => Error::Unhandled(#T::new(err.into())),", unhandledError())
+                        rustTemplate(
+                            "#{errorSymbol}Kind::Unhandled(inner) => Error::Unhandled(#{unhandled}::new(inner.into())),",
+                            "errorSymbol" to errorSymbol,
+                            "unhandled" to unhandledError(),
+                        )
                     }
                 }
             }

diff --git a/rust-runtime/aws-smithy-http/src/result.rs b/rust-runtime/aws-smithy-http/src/result.rs
@@ -122,6 +122,14 @@ impl<E, R> ServiceError<E, R> {
     }
 }
 
+/// Constructs the unhandled variant of a code generated error.
+///
+/// This trait exists so that [`SdkError::into_service_error`] can be infallible.
+pub trait CreateUnhandledError {
+    /// Creates an unhandled error variant with the given `source`.
+    fn create_unhandled_error(source: Box<dyn Error + Send + Sync + 'static>) -> Self;
+}
+
 /// Failed SDK Result
 #[non_exhaustive]
 #[derive(Debug)]
@@ -179,34 +187,42 @@ impl<E, R> SdkError<E, R> {
 
     /// Returns the underlying service error `E` if there is one
     ///
-    /// If a service error is not available (for example, the error is a network timeout),
-    /// then the full `SdkError` is returned. This makes it easy to match on the service's
-    /// error response while simultaneously bubbling up transient failures. For example,
-    /// handling the `NoSuchKey` error for S3's `GetObject` operation may look as follows:
+    /// If the `SdkError` is not a `ServiceError` (for example, the error is a network timeout),
+    /// then it will be converted into an unhandled variant of `E`. This makes it easy to match
+    /// on the service's error response while simultaneously bubbling up transient failures.
+    /// For example, handling the `NoSuchKey` error for S3's `GetObject` operation may look as
+    /// follows:
     ///
     /// ```no_run
-    /// # use aws_smithy_http::result::SdkError;
+    /// # use aws_smithy_http::result::{SdkError, CreateUnhandledError};
     /// # #[derive(Debug)] enum GetObjectErrorKind { NoSuchKey(()), Other(()) }
     /// # #[derive(Debug)] struct GetObjectError { kind: GetObjectErrorKind }
     /// # impl std::fmt::Display for GetObjectError {
     /// #     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { unimplemented!() }
     /// # }
     /// # impl std::error::Error for GetObjectError {}
-    /// # fn example() -> Result<(), Box<dyn std::error::Error>> {
+    /// # impl CreateUnhandledError for GetObjectError {
+    /// #     fn create_unhandled_error(_: Box<dyn std::error::Error + Send + Sync + 'static>) -> Self { unimplemented!() }
+    /// # }
+    /// # fn example() -> Result<(), GetObjectError> {
     /// # let sdk_err = SdkError::service_error(GetObjectError { kind: GetObjectErrorKind::NoSuchKey(()) }, ());
-    /// match sdk_err.into_service_error()? {
+    /// match sdk_err.into_service_error() {
     ///     GetObjectError { kind: GetObjectErrorKind::NoSuchKey(_) } => {
     ///         // handle NoSuchKey
     ///     }
-    ///     err @ _ => return Err(err.into()),
+    ///     err @ _ => return Err(err),
     /// }
     /// # Ok(())
     /// # }
     /// ```
-    pub fn into_service_error(self) -> Result<E, Self> {
+    pub fn into_service_error(self) -> E
+    where
+        E: std::error::Error + Send + Sync + CreateUnhandledError + 'static,
+        R: Debug + Send + Sync + 'static,
+    {
         match self {
-            Self::ServiceError(context) => Ok(context.source),
-            _ => Err(self),
+            Self::ServiceError(context) => context.source,
+            _ => E::create_unhandled_error(self.into()),
         }
     }
 

diff --git a/tools/ci-cdk/canary-lambda/src/s3_canary.rs b/tools/ci-cdk/canary-lambda/src/s3_canary.rs
@@ -34,10 +34,7 @@ pub async fn s3_canary(client: s3::Client, s3_bucket_name: String) -> anyhow::Re
                 CanaryError(format!("Expected object {} to not exist in S3", test_key)).into(),
             );
         }
-        Err(err) => match err
-            .into_service_error()
-            .context("unexpected s3::GetObject failure")?
-        {
+        Err(err) => match err.into_service_error() {
             GetObjectError {
                 kind: GetObjectErrorKind::NoSuchKey(..),
                 ..