Google_Protobuf_Mixin

• If after comment and whitespace stripping, the documentation string of the redeclared method is empty, it will be inherited from the original method.

• Each annotation belonging to the service config (http, visibility) which is not set in the redeclared method will be inherited.

• If an http annotation is inherited, the path pattern will be modified as follows. Any version prefix will be replaced by the version of the including interface plus the [root][] path if specified.

Example of a simple mixin:

package google.acl.v1;
service AccessControl {
  // Get the underlying ACL object.
  rpc GetAcl(GetAclRequest) returns (Acl) {
    option (google.api.http).get = "/v1/{resource=**}:getAcl";
  }
}

package google.storage.v2;
service Storage {
  rpc GetAcl(GetAclRequest) returns (Acl);

  // Get a data record.
  rpc GetData(GetDataRequest) returns (Data) {
    option (google.api.http).get = "/v2/{resource=**}";
  }
}

Example of a mixin configuration:

apis:
- name: google.storage.v2.Storage
  mixins:
  - name: google.acl.v1.AccessControl

The mixin construct implies that all methods in AccessControl are also declared with same name and request/response types in Storage. A documentation generator or annotation processor will see the effective Storage.GetAcl method after inheriting documentation and annotations as follows:

service Storage {
  // Get the underlying ACL object.
  rpc GetAcl(GetAclRequest) returns (Acl) {
    option (google.api.http).get = "/v2/{resource=**}:getAcl";
  }
  ...
}

Note how the version in the path pattern changed from v1 to v2.

If the root field in the mixin is specified, it should be a relative path under which inherited HTTP paths are placed. Example:

apis:
- name: google.storage.v2.Storage
  mixins:
  - name: google.acl.v1.AccessControl
    root: acls

This implies the following inherited HTTP annotation:

service Storage {
  // Get the underlying ACL object.
  rpc GetAcl(GetAclRequest) returns (Acl) {
    option (google.api.http).get = "/v2/acls/{resource=**}:getAcl";
  }
  ...
}