Operation BodyMediaType is not set correctly.

[m-nash]

For this cadl ranch spec we can see that operation sendAsJson is marked with application/json yet the RequestBodyMediaType comes out as Text instead of Json.

[m-nash]

from @archerzz

Looks like it's a legacy problem. I search the codes, and we have two properties regarding media types in
InputOperation
:

RequestBodyMediaType: It's determined by the request body parameter type

typespec/packages/http-client-csharp/emitter/src/lib/operation-converter.ts

Line 92 in 2d4f55f

RequestBodyMediaType: getBodyMediaType(method.operation.bodyParam?.type),

It's not used in MGC.
In autorest.csharp, it's used by CmcRestClientBuilder and RestClientBuilder
RequestMediaTypes: it's determined by scanning the operation, which I think is more accurate

typespec/packages/http-client-csharp/emitter/src/lib/operation-converter.ts

Line 96 in 2d4f55f

RequestMediaTypes: getRequestMediaTypes(method.operation),

It's not used in MGC either (probably MGC hasn't implement the various media type support?)
In autoest.csharp:
it's used by OperationMethodChainBuilder when setting the request Content-Type header: https://github.com/Azure/autorest.csharp/blob/a19bafb7ff7418930deb75b1df40ccbf55825228/src/AutoRest.CSharp/LowLevel/Output/OperationMethodChainBuilder.cs#L557
it's used by ConvenienceMethod when determine how to serialize the input body: https://github.com/Azure/autorest.csharp/blob/a19bafb7ff7418930deb75b1df40ccbf55825228/src/AutoRest.CSharp/LowLevel/Output/ConvenienceMethod.cs#L36
So that's why DPG is not impacted. It correctly consumes only RequestMediaTypes. All others are using RequestBodyMediaType.

[m-nash]

#4215 follow up to remove dupe

[m-nash]

@archerzz this fixed it partially, but for this operation, the RequestMediaTypes is null so we fail that check that looks for text/plain.

You can repro by running this test https://github.com/Azure/cadl-ranch/blob/main/packages/cadl-ranch-specs/http/payload/media-type/main.tsp#L32-L35

[archerzz]

@archerzz this fixed it partially, but for this operation, the RequestMediaTypes is null so we fail that check that looks for text/plain.

You can repro by running this test Azure/cadl-ranch@main/packages/cadl-ranch-specs/http/payload/media-type/main.tsp#L32-L35

@m-nash That's another legacy issue. We always hard-code the response media type to json, see

typespec/packages/http-client-csharp/emitter/src/lib/operation-converter.ts

Line 255 in d9faa2a

BodyMediaType: BodyMediaType.Json,

I traced back to the original autorest.csharp emitter, and I think the hard-coded value has existed for quite a long time: https://github.com/Azure/autorest.csharp/blob/0fb10e0dec33253e9db8b7fae05d311abf9f76ed/src/TypeSpec.Extension/Emitter.Csharp/src/lib/operation.ts#L390

So, I think we need to remove not only InputOperation.RequestBodyMediaType, but the BodyMediaType enum and corresponding reference as well.

---

I filed #4225 to track that.

[archerzz]

Update on Jan 9, 2025. Last time when we discussed about this issue, it's decided that we should come up with an overall solution on how we're going to deal with media types.

Right now, there are duplicated properties and hard coded values. We need to:

1. Clean up duplicated properties
2. Remove hard coded values
3. Figure out an extensible way to support various media types

That will generate substantial impact on our current codes both in MGC and autorest.csharp.

[JoshLove-msft]

@archerzz do you have an idea of a timeline for when you will work on this?

[ArcturusZhang]

So in our latest update, this property and related logic have been removed: #6119
Therefore I think this should have been fixed.
Closing this issue