feat(cli): add responses for PingController.ping()

[raymondfeng]

Fixes #1754

Checklist

• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated

[bajtos]

Please add an explicit type SchemaObject to let the compiler verify correctness of the schema here, where we are defining PING_RESPONSE, instead of deferring the check until PING_RESPONSE is assigned to responses in @get below.

const PING_RESPONSE: SchemaObject = {
  // ...
};

[bajtos]

The test name feels misleading to me. We are not testing the entire OpenAPI spec, only the spec of GET /ping endpoint here. How about:

it('provides a valid OpenAPI spec for "GET /ping"', async () => {
 // ...
});

Personally, I don't think we have to make an HTTP request to test that, I would move this test to src/test/integration and obtain the spec via app.restServer.getApiSpec(). Such test will be much more resilient against possible changes of /openapi.json location in the future.

I see the value in a test obtaining the spec via HTTP. I think such test should go to test/acceptance/application.acceptance.ts and verify that the returned spec is valid.

import {validateApiSpec} from '@loopback/testlab';

describe('TodoApplication' /* use the real app class name */, () => {
  it('exposes valid OpenAPI spec at /openapi.json', async () => {
    const res = await client.get('/openapi.json').expect(200);
    await validateApiSpec(res.body);
  });
});

I am ok with leaving such test out of scope of this pull request if you prefer.

[raymondfeng]

@bajtos I added typing for PING_RESPONSE and removed the /openapi.json test from the PR. PTAL.

[bajtos]

Can we import ResponseObject from @loopback/rest directly? I believe our rest package is re-exporting OAS types for ease of use.

We are going to remove @loopback/openapi-v3-types soon (before 4.0 GA), see #301.

[raymondfeng]

I was concerned about microsoft/TypeScript#26985. Will double-check.

[raymondfeng]

I add the code to re-export @loopback-v3-types from @loopback-rest.

[bajtos]

I prefer to import OAS types from @loopback/rest, see my comment above.

[bajtos]

Ditto.