Duplicate Body Error When Instantiating `ProxyResourceOperations`

When instantiating the ProxyResourceOperations<TResource> template with an incorrect second parameter, a “duplicate body” error like the following may result:

error @typespec/http/duplicate-body Operation has a @body and an unannotated parameter. There can only be one representing the body

Symptoms

When instantiating the ProxyResourceOperations<TResource> template, it is easy to assume that the second parameter should contain the RP-specific properties of the resource, as with the TrackedResourceOperations<TResource, TProperties> template.

// INCORRECT USAGE OF THE TEMPLATE
interface MyResourceOperations extends ProxyResourceOperations<MyResource, MyResourceProperties> {}

However, this usage is incorrect, the second parameter to ProxyResourceOperations is optional and, if provided, is expecting an entirely different TypeSpec type. If the resource properties are supplied instead, a “duplicate body” error like the following will result:

error @typespec/http/duplicate-body Operation has a @body and an unannotated parameter. There can only be one representing the body

Cause

This error occurs because the second parameter is an optional override for the shared request parameters for the read, createOrUpdate, and delete operations for the proxy resource. When the rp-specific properties are provided instead, the operation request parameters clash with the request body parameter for createOrUpdate.

Workaround

To fix this error, provide only one parameter to ProxyResourceOperations, the type of the resource that the operations apply to.

// CORRECT
interface MyResourceOperations extends ProxyResourceOperations<MyResource> {}