[BUG] Compiler generates $batch request for REST service

[lucasvaccaro]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

When a CDS service is annotated with @protocol: 'rest', the OpenAPI compiler still generates a /$batch path item in the output, but it is specific to OData.

Expected Behavior

The compiler should not generate /$batch endpoint for REST services.

Steps To Reproduce

1. Define a REST CDS service:

@path    : '/rest/v1/myRestAPI'
@protocol: 'rest'
service MyRestAPI {
  action send();
}

2. cds compile <file>.cds --to openapi
3. Inspect the generated file

Environment

| Package                | Version | Location                                                   |
 | ---------------------- | ------- | ---------------------------------------------------------- |
 | @sap/cds-dk            | 9.9.1   | ./node_modules/@sap/cds-dk                                 |
 | @sap/cds               | 9.6.4   | ./node_modules/@sap/cds                                    |
 | @sap/cds-compiler      | 6.6.2   | ./node_modules/@sap/cds-compiler                           |
 | @sap/cds-fiori         | 2.1.1   | ./node_modules/@sap/cds-fiori                              |
 | @sap/cds-mtxs          | 3.9.7   | ./node_modules/@sap/cds-mtxs                               |
 | @cap-js/asyncapi       | 1.1.0   | ./node_modules/@cap-js/asyncapi                            |
 | @cap-js/cds-test       | 0.4.1   | ./node_modules/@cap-js/cds-test                            |
 | @cap-js/cds-types      | 0.15.0  | ./node_modules/@cap-js/cds-types                           |
 | @cap-js/db-service     | 2.8.1   | ./node_modules/@cap-js/db-service                          |
 | @cap-js/hana           | 2.5.1   | ./node_modules/@cap-js/hana                                |
 | @cap-js/openapi        | 1.6.0   | ./node_modules/@cap-js/openapi                             |
 | @cap-js/ord            | 1.9.3   | ./node_modules/@cap-js/ord                                 |
 | @cap-js/sqlite         | 2.1.2   | ./node_modules/@cap-js/sqlite                              |
 | @cap-js/sqlite         | 2.4.0   | ./node_modules/@sap/cds-dk/node_modules/@cap-js/sqlite     |
 | @cap-js/telemetry      | 2.0.1   | ./node_modules/@cap-js/telemetry                           |
 | @sap/eslint-plugin-cds | 2.7.0   | ./node_modules/@sap/eslint-plugin-cds                      |
 | cds.home               |         | ./node_modules/@sap/cds                                    |
 | npm root -l            |         | ./node_modules                                             |
 | npm root -g            |         | ~/.nvm/versions/node/v22.23.1/lib/node_modules             |
 | Node.js                | 22.23.1 | ~/.nvm/versions/node/v22.23.1/bin/node                     |

Repository Containing a Minimal Reproducible Example

No response

Anything else?

There is a workaround by annotating the service with @Capabilities.BatchSupported: false, so there is no urgency in this one.