feat: add allowDefault option to operation-2xx-response

.changeset/olive-pugs-repeat.md

@@ -0,0 +1,6 @@
+---
+'@redocly/openapi-core': minor
+'@redocly/cli': minor
+---
+
+Added an `allowDefault` option to the `operation-2xx-response` rule, which controls whether a `default` response satisfies the rule. Defaults to `true`, matching the previous behavior.

docs/@v2/rules/oas/operation-2xx-response.md

@@ -28,6 +28,7 @@ You can greatly improve the developer and user experience of your APIs by making
 | ---------------- | ------- | ----------------------------------------------------------------------------------------- |
 | severity         | string  | Possible values: `off`, `warn`, `error`. Default `warn` (in `recommended` configuration). |
 | validateWebhooks | boolean | Determines if responses inside webhooks are validated. Default `false`.                   |
+| allowDefault     | boolean | Determines if a `default` response satisfies the rule. Default `true`.                    |
 
 An example configuration:
 
@@ -45,6 +46,28 @@ rules:
     validateWebhooks: true
 ```
 
+By default, a `default` response counts as a successful response.
+Set `allowDefault: false` to require an explicit 2xx status code:
+
+```yaml
+rules:
+  operation-2xx-response:
+    severity: error
+    allowDefault: false
+```
+
+With `allowDefault: false`, the following operation is reported, because `default` describes the responses the operation does not list rather than what a successful call returns:
+
+```yaml
+post:
+  responses:
+    default:
+      $ref: ../components/responses/Problem.yaml
+```
+
+This matters for code generation: a generator reads the 2xx response to produce the return type of the operation.
+A `default`-only operation gives it no success shape to model, so the generated client falls back to an untyped or empty result.
+
 ## Examples
 
 Given this configuration:

packages/core/src/rules/common/__tests__/operation-2xx-response.test.ts

@@ -92,6 +92,50 @@ describe('Oas3 operation-2xx-response', () => {
     expect(replaceSourceWithRef(results)).toMatchInlineSnapshot(`[]`);
   });
 
+  it('should report for present default when allowDefault is false', async () => {
+    const document = parseYamlToDocument(
+      outdent`
+          openapi: 3.0.0
+          paths:
+            '/test/':
+              put:
+                responses:
+                  default:
+                    description: ok
+        `,
+      'foobar.yaml'
+    );
+
+    const results = await lintDocument({
+      externalRefResolver: new BaseResolver(),
+      document,
+      config: await createConfig({
+        rules: {
+          'operation-2xx-response': { severity: 'error', allowDefault: false },
+        },
+      }),
+    });
+
+    expect(replaceSourceWithRef(results)).toMatchInlineSnapshot(`
+      [
+        {
+          "location": [
+            {
+              "pointer": "#/paths/~1test~1/put/responses",
+              "reportOnKey": true,
+              "source": "foobar.yaml",
+            },
+          ],
+          "message": "Operation must have at least one \`2XX\` response.",
+          "reference": "https://redocly.com/docs/cli/rules/oas/operation-2xx-response",
+          "ruleId": "operation-2xx-response",
+          "severity": "error",
+          "suggest": [],
+        },
+      ]
+    `);
+  });
+
   it('should report even if the responses are null', async () => {
     const document = parseYamlToDocument(
       outdent`

packages/core/src/rules/common/operation-2xx-response.ts

@@ -2,7 +2,10 @@ import type { Oas3Rule, Oas2Rule } from '../../visitors.js';
 import type { UserContext } from '../../walk.js';
 import { validateResponseCodes } from '../utils.js';
 
-export const Operation2xxResponse: Oas3Rule | Oas2Rule = ({ validateWebhooks }) => {
+export const Operation2xxResponse: Oas3Rule | Oas2Rule = ({
+  validateWebhooks,
+  allowDefault = true,
+}) => {
   return {
     Paths: {
       Responses(responses: Record<string, object>, { report }: UserContext) {
@@ -13,6 +16,7 @@ export const Operation2xxResponse: Oas3Rule | Oas2Rule = ({ validateWebhooks })
           codeRange: '2XX',
           report: report as UserContext['report'],
           reference: 'https://redocly.com/docs/cli/rules/oas/operation-2xx-response',
+          allowDefault,
         });
       },
     },
@@ -27,6 +31,7 @@ export const Operation2xxResponse: Oas3Rule | Oas2Rule = ({ validateWebhooks })
           codeRange: '2XX',
           report: report as UserContext['report'],
           reference: 'https://redocly.com/docs/cli/rules/oas/operation-2xx-response',
+          allowDefault,
         });
       },
     },

packages/core/src/rules/utils.ts

@@ -390,17 +390,19 @@ export function validateResponseCodes({
   codeRange,
   report,
   reference,
+  allowDefault = true,
 }: {
   responseCodes: string[];
   codeRange: string;
   report: UserContext['report'];
   reference?: string;
+  allowDefault?: boolean;
 }) {
   const responseCodeRegexp = new RegExp(`^${codeRange[0]}[0-9Xx]{2}$`);
 
   const containsNeededCode = responseCodes.some(
     (code) =>
-      (codeRange === '2XX' && code === 'default') || // It's OK to replace 2xx codes with the default
+      (allowDefault && codeRange === '2XX' && code === 'default') || // It's OK to replace 2xx codes with the default
       responseCodeRegexp.test(code)
   );