better response type handling

[hauner]

If an api has multiple response content types (success & errors) the java response type of the controller method will be Object to allow return values with different java types.

If the errors are handled by throwing an exception there is no need to have an Object response and the controller method could use the type of the success response to improve readability of the interface.

mapping could be like this, using a globally applied option:

# mapping.yaml
openapi-processor-mapping: v2

options:
  response-type: all    # all (default) or success

or like this, allowing endpoint & endpoint/method configuration:

# mapping.yaml
openapi-processor-mapping: v2

map:
  response-type: all    # all (default) or success

all: consider all response types to select the method return type
success: consider only the success response type, i.e. usually 200

[JonasGroeger]

In the Spring module this is also annoying since even if you put

map:
  result: org.springframework.http.ResponseEntity

it will generate ResponseEntity<?> and not ResponseEntity<SuccessResponse>.

Could you give me some hints on how you would implement it? I'm willing to write an implementation.

Reference: https://docs.openapiprocessor.io/spring/2021.3/mapping/result.html

[hauner]

Yes, I think that has the same cause.

Thanks for the offer to help -)

Here are a few notes to get you started.

I did a few lines on this to get the new option but that's just a minimal start that does not yet do anything. It is on this branch: https://github.com/openapi-processor/openapi-processor-core/tree/response-type-handling

Current idea is to replace the return type of the controller method in the MethodWriter here:

openapi-processor-core/src/main/kotlin/io/openapiprocessor/core/writer/java/MethodWriter.kt

Line 47 in e25f7ab

| ${endpointResponse.responseType} ${createMethodName (endpoint, endpointResponse)}(${createParameters(endpoint)});

This is the line that adds the response type to the method. Replacing ${endpointResponse.responseType} with a method that does select the return type based on the new option should solve the issue. If the new option is all use the current behaviour if it is success use the success response type and ignore the error responses.

The code to get the wanted type exists and is currently private in the EndpointResponse:

openapi-processor-core/src/main/kotlin/io/openapiprocessor/core/model/EndpointResponse.kt

Line 37 in e25f7ab

val responseType: String

Note that the identical selection is required to create the import list.

Getting that option is probably the harder part. Converting the mapping.yaml to the internal format requires a couple of steps and is more complex than I like.

If the options is configured like this

# mapping.yaml
openapi-processor-mapping: v2

map:
  response-type: all    # all (default) or success

the MethodWriter will need the MappingFinder to get access to it and then call a similiar function to

openapi-processor-core/src/main/kotlin/io/openapiprocessor/core/converter/mapping/MappingFinder.kt

Line 122 in e25f7ab

fun findResultTypeMapping(): ResultTypeMapping? {

to get the value of new mapping option.

The maps: part of the mapping.yaml is converted internally to Mappings. The MappingFinder uses them to find & select mappings.

The new option will need a new implementation of the Mapping interface: https://github.com/openapi-processor/openapi-processor-core/blob/response-type-handling/src/main/kotlin/io/openapiprocessor/core/converter/mapping/Mapping.kt

Converting the yaml to the Mapping happens here:
https://github.com/openapi-processor/openapi-processor-core/blob/response-type-handling/src/main/kotlin/io/openapiprocessor/core/processor/mapping/v2/MappingConverter.kt

I hope this helps and i didn't miss any annoying detail that breaks this approach :)

[hauner]

collecting the import happens here

openapi-processor-core/src/main/kotlin/io/openapiprocessor/core/writer/java/InterfaceWriter.kt

Line 65 in e25f7ab

private fun collectImports(packageName: String, endpoints: List<Endpoint>): List<String> {

[hauner]

@JonasGroeger Hi, I have it nearly running.... I hope you didn't waste to much on on it.