Warning when 422 is used

baloise.yml

@@ -98,6 +98,15 @@ rules:
           - '505'
           - '511'
           - default
+  must-use-additional-standard-http-status-codes-422:
+    message: 'Prefer 400 over 422 as response code'
+    description: MUST use standard HTTP status codes [150a]
+    documentationUrl: https://github.com/baloise-incubator/spectral-ruleset/blob/main/doc/rules/must-use-additional-standard-http-status-codes.md
+    severity: warn
+    given: $.paths.*.*.responses.422
+    then:
+      field: '422'
+      function: defined
 
   should-use-well-understood-http-status-codes: off
 

doc/rules/must-use-additional-standard-http-status-codes.md

@@ -1,3 +1,4 @@
 # MUST use standard http status codes [150a]
 
-We will also add 422 status code to allowed codes defined by [zalando](https://opensource.zalando.com/restful-api-guidelines/#150).
+We will also add 422 status code to allowed codes defined by [zalando](https://opensource.zalando.com/restful-api-guidelines/#150).  
+But you should prefer 400 over 422.

tests/150a-MUST-use-additional-standard-HTTP-status-codes.test.ts

@@ -229,4 +229,23 @@ describe('MUST use additional standard HTTP status codes [150a]', () => {
       ]),
     );
   });
+
+  test('Detect 422 HTTP status codes for operations and warn', async () => {
+    const openApi = await loadOpenApiSpec('base-openapi.yml');
+    openApi.paths['/example'] = {
+      post: {
+        responses: {
+          '422': {},
+        },
+      },
+    };
+    const result = await lint(openApi, 'baloise');
+    expect(result).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          message: `Prefer 400 over 422 as response code`,
+        }),
+      ]),
+    );
+  });
 });