Generate client method signature which follow the serivce operation signature.

Different language may have different interpretation of the signature, based on best practise of that language.

Interprecate model as class

Model ClientOptions

@resource("resource-collection")
model Resource {
  @key name: string;
  prop1: string;
  prop2?: string;
}

model ClientOptions {
  @header headerParam?: string;
  ...Resource;
}

op put is ResourceCreateOrReplace<ClientOptions>;

Generates

Resource put(ClientOptions clientOptions);

While anonymous model

alias ClientOptions {
  @header headerParam?: string;
  ...Resource;
}

op put is ResourceCreateOrReplace<ClientOptions>;

Generates the usual param + body signature

Resource put(String name, Resource resource, String headerParam);

• We can see some problem here. @key name in Resource also means the path parameter. Should it be in Resource class as well (instead of name in method argument)? And then think about @parentResource.
• Other problem would be that some header would be from Traits, e.g. SupportsConditionalRequests related trait that supplies if-match headers.

Mix of model and anonymous model for arguments

@resource("resource-collection")
model Resource {
  @key name: string;
  prop1: string;
}

model RequiredClientOptions {
  ...Resource;
}

model OptionalClientOptions {
  @header headerParam?: string;
  prop2?: string;
}

op put is ResourceCreateOrReplace<{@header headerParam2?: string, ...RequiredClientOptions, ...OptionalClientOptions}>;

Generates

Resource put(RequiredClientOptions requiredClientOptions, OptionalClientOptions optionalClientOptions, String headerParam2);

• {...RequiredClientOptions, ...OptionalClientOptions} part is already tricky.
• And SDK still need to order optional argument to last. So it never able to follow the service operation exactly.

Personal opinion

Pro

• The service operation could directly affect client method signature.
• Language can make different interpretation that best suits its best practise (e.g. Python may avoid taking ClientOptions as class at all).

Con

• It is hard to understand, especially when it coupled with template, trait, and resource (that would each contribute some path/query/header parameter).
• Different interpretation could further degrade readability.