Check for polymorphic child schemas in search for request schemas

functions/readonly-in-response-schema.js

@@ -1,11 +1,13 @@
 // Flag any properties that are readonly in the response schema.
 
 // Scan an OpenAPI document to determine if a schema is a response-only schema,
-// which means it is not references by any request schemas.
+// which means it is not referenced by any request schemas.
 // Any schema that is referenced by a request is considered a request schema.
 // Any schema referenced by a request schema is also considered a request schema.
+// Any schema that "allOf"'s a request schema with a discriminator is also a request schema.
 // Any schema that is not a request schema is considered a response-only schema.
 
+// requestSchemas is a set of schema names that we have determined are request schemas
 let requestSchemas;
 
 function getRequestSchemas(oasDoc) {
@@ -64,6 +66,17 @@ function getRequestSchemas(oasDoc) {
           }
         }
       }
+      if (schema.discriminator) {
+        // Check all the schemas in the document and add any that "allOf" this schema
+        // into schemasToProcess
+        const schemaRef = `#/definitions/${schemaName}`;
+        // eslint-disable-next-line no-restricted-syntax
+        for (const [key, value] of Object.entries(oasDoc.definitions)) {
+          if (value.allOf?.some((elem) => elem.$ref === schemaRef)) {
+            schemasToProcess.push(key);
+          }
+        }
+      }
     }
   }
 }

test/readonly-in-response-schema.test.js

@@ -93,6 +93,24 @@ test('az-readonly-in-response-schema should not find errors', () => {
           },
         },
       },
+      '/test2': {
+        post: {
+          parameters: [
+            {
+              in: 'body',
+              name: 'body',
+              schema: {
+                $ref: '#/definitions/Pet',
+              },
+            },
+          ],
+          responses: {
+            200: {
+              description: 'Success',
+            },
+          },
+        },
+      },
     },
     definitions: {
       Model1: {
@@ -155,6 +173,29 @@ test('az-readonly-in-response-schema should not find errors', () => {
           },
         },
       },
+      Pet: {
+        discriminator: 'petType',
+      },
+      Dog: {
+        type: 'object',
+        allOf: [{ $ref: '#/definitions/Pet' }],
+        properties: {
+          cute: {
+            type: 'number',
+            readOnly: true,
+          },
+        },
+      },
+      Cat: {
+        type: 'object',
+        allOf: [{ $ref: '#/definitions/Pet' }],
+        properties: {
+          attitude: {
+            type: 'string',
+            readOnly: true,
+          },
+        },
+      },
     },
   };
   return linter.run(oasDoc).then((results) => {