EventStreamUnmarshallerGeneratorTest is running misconfigured tests for the server

[david-perez]

The tests in EventStreamUnmarshallerGeneratorTest.kt are being run for the server because in EventStreamTestTools.kt we have:

https://github.com/awslabs/smithy-rs/blob/242e6bcd677b5600f27106f8bc45f411c3c429da/codegen/src/test/kotlin/software/amazon/smithy/rust/codegen/smithy/protocols/EventStreamTestTools.kt#L306-L306

That is, each test case is duplicated: one with CodegenTarget.CLIENT, one with CodegenTarget.SERVER.

The problem is this is incorrect, because both test types are using the testSymbolProvider from TestHelpers.kt

https://github.com/awslabs/smithy-rs/blob/242e6bcd677b5600f27106f8bc45f411c3c429da/codegen/src/main/kotlin/software/amazon/smithy/rust/codegen/testutil/TestHelpers.kt#L66-L71

That is the symbol provider that the client uses, which is very different from the server one (for example, the client generates Optional types for @required members, and the server doesn't).

It should instead be using serverTestSymbolProvider:

https://github.com/awslabs/smithy-rs/blob/242e6bcd677b5600f27106f8bc45f411c3c429da/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/testutil/ServerTestHelpers.kt#L30-L35

However, we can't make it use that symbol provider, because the server symbol provider is in ServerTestHelpers.kt, part of the codegen-server subproject's test sources. But EventStreamUnmarshallerGeneratorTest.kt is in the codegen subproject. codegen cannot depend on codegen-server, it's the other way around.

One way to fix this would be to have codegen-server's test sources depend on codegen's test sources. We would rewrite the test case provider in the server subproject to use the serverTestSymbolProvider, and then the test would just delegate to EventStreamUnmarshallerGeneratorTest.kt passing it the modified test case. I've tried looking into this and it's not straightforward.

• How to share test classes across Gradle projects?
• Multi-project test dependencies with gradle

The examples above are in Groovy; I don't know how to do it in the Kotlin DSL. Gradle's official documentation seems to recommend the testFixtures approach for sharing test code across projects, but in our case we would not only want to share the test cases but also the test code from EventStreamUnmarshallerGeneratorTest.kt. I don't know if that's abusing the testFixtures pattern.

To me it seems like this is yet another indication that we should restructure smithy-rs to have three subprojects: a core library, the client plugin, and the server plugin. Both the client and server plugins would depend on the core library's implementation and test code.

[rcoh]

To me it seems like this is yet another indication that we should restructure smithy-rs to have three subprojects: a core library, the client plugin, and the server plugin. Both the client and server plugins would depend on the core library's implementation and test code.

I'm definitely in favor of this