Unverified Commit fc63800f authored by Antoine Büsch's avatar Antoine Büsch Committed by GitHub
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Implement `StdError::source()` for Error enum (#2564) 

## Motivation and Context
This is an attempt at fixing
https://github.com/awslabs/aws-sdk-rust/issues/784.

The service-level `Error` enum implements `std::error::Error` but does
not implement its `source()` method. This means that an error library
like `anyhow` or `eyre` won't be able to display the root cause of an
error, which is especially problematic for the `Unhandled` variant.

## Description
I modified `ServiceErrorGenerator` in the `codegen-client` crate and
replaced the line that output `impl std::error::Error for Error {}` with
an impl block that implements the `source()` method by delegating to the
inner error structure.

## Testing
I've added a simple unit test to `ServiceErrorGeneratorTest`.

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the AWS
SDK, generated SDK code, or SDK runtime crates

----

_By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice._
parent 35f2f27a

CHANGELOG.next.toml

+12 −0
Original line number Diff line number Diff line
@@ -11,6 +11,18 @@ 
# meta = { "breaking" = false, "tada" = false, "bug" = false, "target" = "client | server | all"}

# author = "rcoh"



[[aws-sdk-rust]]

message = "Implement std::error::Error#source() properly for the service meta Error enum"

references = ["aws-sdk-rust#784"]

meta = { "breaking" = false, "tada" = false, "bug" = false }

author = "abusch"



[[smithy-rs]]

message = "Implement std::error::Error#source() properly for the service meta Error enum"

references = ["aws-sdk-rust#784"]

meta = { "breaking" = false, "tada" = false, "bug" = false, "target" = "client"}

author = "abusch"



[[aws-sdk-rust]]

message = "The outputs for event stream operations (for example, S3's SelectObjectContent) now implement the `Sync` auto-trait."

references = ["smithy-rs#2496"]

codegen-client/src/main/kotlin/software/amazon/smithy/rust/codegen/client/smithy/generators/error/ServiceErrorGenerator.kt

+10 −1
Original line number Diff line number Diff line
@@ -80,7 +80,16 @@ class ServiceErrorGenerator( 
                        errors.map { it.id },

                    )

                }

            rust("impl #T for Error {}", RuntimeType.StdError)

            rustBlock("impl #T for Error", RuntimeType.StdError) {

                rustBlock("fn source(&self) -> std::option::Option<&(dyn #T + 'static)>", RuntimeType.StdError) {

                    rustBlock("match self") {

                        allErrors.forEach {

                            rust("Error::${symbolProvider.toSymbol(it).name}(inner) => inner.source(),")

                        }

                        rust("Error::Unhandled(inner) => inner.source()")

                    }

                }

            }

            writeCustomizations(customizations, ErrorSection.ServiceErrorAdditionalTraitImpls(allErrors))

        }

        crate.lib { rust("pub use error_meta::Error;") }

codegen-client/src/test/kotlin/software/amazon/smithy/rust/codegen/client/smithy/generators/error/ServiceErrorGeneratorTest.kt

+49 −25
Original line number Diff line number Diff line
@@ -6,15 +6,16 @@ 
package software.amazon.smithy.rust.codegen.client.smithy.generators.error



import org.junit.jupiter.api.Test

import software.amazon.smithy.model.shapes.StructureShape

import software.amazon.smithy.rust.codegen.client.testutil.clientIntegrationTest

import software.amazon.smithy.rust.codegen.core.rustlang.rust

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.unitTest

import software.amazon.smithy.rust.codegen.core.util.lookup



internal class ServiceErrorGeneratorTest {

    @Test

    fun `top level errors are send + sync`() {

        val model = """

    private val model = """

        namespace com.example



        use aws.protocols#restJson1
@@ -45,6 +46,8 @@ internal class ServiceErrorGeneratorTest { 
        structure MeDeprecated { }

    """.asSmithyModel()



    @Test

    fun `top level errors are send + sync`() {

        clientIntegrationTest(model) { codegenContext, rustCrate ->

            rustCrate.integrationTest("validate_errors") {

                rust(
@@ -60,4 +63,25 @@ internal class ServiceErrorGeneratorTest { 
            }

        }

    }



    @Test

    fun `generates combined error enums`() {

        clientIntegrationTest(model) { _, rustCrate ->

            rustCrate.moduleFor(model.lookup<StructureShape>("com.example#CanYouRepeatThat")) {

                unitTest(

                    name = "generates_combined_error_enums",

                    test = """

                        use std::error::Error as StdError;

                        use crate::Error;

                        use crate::operation::say_hello::SayHelloError;



                        // Unhandled variants properly delegate source.

                        let error = Error::from(SayHelloError::unhandled("some other error"));

                        let source = error.source().expect("source should not be None");

                        assert_eq!(format!("{}", source), "some other error");

                    """,

                )

            }

        }

    }

}