fix(core): fix Ajv error discriminator

.changeset/sixty-falcons-glow.md

@@ -0,0 +1,6 @@
+---
+"@redocly/respect-core": patch
+"@redocly/openapi-core": patch
+---
+
+Fixed AJV validation error when schemas use a discriminator property with complex constraint patterns like `allOf + not`.AJV's `discriminator: true` option requires every discriminator property to have a direct `const` or `enum`, which is incompatible with valid OpenAPI schemas that use composition patterns. Disabled AJV's discriminator keyword in both the respect schema checker and lint example validation, and removed the silent error swallowing in `validateExample` that was skipping validation for schemas with discriminators.

packages/core/src/rules/ajv.ts

@@ -42,7 +42,7 @@ function getAjv(resolve: ResolveFn, dialect: AjvDialect): AnyAjv {
       strictSchema: false,
       inlineRefs: false,
       validateSchema: false,
-      discriminator: true,
+      discriminator: false,
       allowUnionTypes: true,
       validateFormats: true,
       passContext: true,

packages/core/src/rules/oas3/__tests__/no-invalid-media-type-examples.test.ts

@@ -692,7 +692,7 @@ describe('no-invalid-media-type-examples', () => {
     `);
   });
 
-  it('should not report if allOf used with discriminator', async () => {
+  it('should validate example against schema with allOf and discriminator', async () => {
     const document = parseYamlToDocument(
       outdent`
         openapi: 3.0.0

packages/core/src/rules/utils.ts

@@ -184,10 +184,6 @@ export function validateExample(
       }
     }
   } catch (e) {
-    if (e.message === 'discriminator: requires oneOf or anyOf composite keyword') {
-      return;
-    }
-
     report({
       message: `Example validation errored: ${e.message}.`,
       location: parentLocation.child('schema'),

packages/respect-core/src/modules/__tests__/flow-runner/schema/schema-checker.test.ts

@@ -401,6 +401,118 @@ describe('checkSchema', () => {
     ]);
   });
 
+  it('should pass schema check for discriminator with allOf + not pattern', () => {
+    const discriminatorDescriptionOperation = {
+      ...descriptionOperation,
+      responses: {
+        '200': {
+          description: 'successful operation',
+          content: {
+            'application/json': {
+              schema: {
+                oneOf: [
+                  {
+                    type: 'object',
+                    properties: {
+                      method: {
+                        allOf: [
+                          { enum: ['cash', 'payment-card', 'paypal'] },
+                          { not: { enum: ['payment-card', 'paypal'] } },
+                        ],
+                      },
+                    },
+                  },
+                  {
+                    type: 'object',
+                    properties: {
+                      method: { const: 'payment-card' },
+                    },
+                  },
+                ],
+                discriminator: { propertyName: 'method' },
+              },
+            },
+          },
+        },
+      },
+    };
+
+    const result = checkSchema({
+      stepCallCtx: {
+        ...stepCallCtx,
+        $response: {
+          body: { method: 'cash' },
+          statusCode: 200,
+          header: { 'content-type': 'application/json' },
+          contentType: 'application/json',
+        },
+      } as unknown as StepCallContext,
+      descriptionOperation: discriminatorDescriptionOperation,
+      ctx,
+    });
+
+    const schemaCheck = result.find((c) => c.name === CHECKS.SCHEMA_CHECK);
+    expect(schemaCheck).toBeDefined();
+    expect(schemaCheck?.passed).toBe(true);
+    expect(schemaCheck?.message).not.toContain('Ajv error');
+  });
+
+  it('should fail schema check for discriminator with allOf + not when body does not match', () => {
+    const discriminatorDescriptionOperation = {
+      ...descriptionOperation,
+      responses: {
+        '200': {
+          description: 'successful operation',
+          content: {
+            'application/json': {
+              schema: {
+                oneOf: [
+                  {
+                    type: 'object',
+                    properties: {
+                      method: {
+                        allOf: [
+                          { enum: ['cash', 'payment-card', 'paypal'] },
+                          { not: { enum: ['payment-card', 'paypal'] } },
+                        ],
+                      },
+                    },
+                  },
+                  {
+                    type: 'object',
+                    properties: {
+                      method: { const: 'payment-card' },
+                    },
+                  },
+                ],
+                discriminator: { propertyName: 'method' },
+              },
+            },
+          },
+        },
+      },
+    };
+
+    const result = checkSchema({
+      stepCallCtx: {
+        ...stepCallCtx,
+        $response: {
+          body: { method: 'bitcoin' },
+          statusCode: 200,
+          header: { 'content-type': 'application/json' },
+          contentType: 'application/json',
+        },
+      } as unknown as StepCallContext,
+      descriptionOperation: discriminatorDescriptionOperation,
+      ctx,
+    });
+
+    const schemaCheck = result.find((c) => c.name === CHECKS.SCHEMA_CHECK);
+    expect(schemaCheck).toBeDefined();
+    expect(schemaCheck?.passed).toBe(false);
+    expect(schemaCheck?.message).not.toContain('Ajv error');
+  });
+
   it('should return empty checks if no response available', () => {
     const stepCtx = {
       $request: {

packages/respect-core/src/modules/flow-runner/schema/schema-checker.ts

@@ -20,7 +20,7 @@ const ajvStrict = new Ajv({
   strictSchema: false,
   inlineRefs: false,
   validateSchema: false,
-  discriminator: true,
+  discriminator: false,
   allowUnionTypes: true,
   validateFormats: true,
   logger: false,
@@ -79,18 +79,14 @@ function checkSchemaFromDescription({
 
   if (schemaFromDescription && !isSchemaWithCircularRef) {
     try {
+      const processedSchema = removeWriteOnlyProperties(
+        schemaFromDescription as JSONSchemaType<unknown>
+      );
       checks.push({
         name: CHECKS.SCHEMA_CHECK,
-        passed: ajvStrict.validate(
-          removeWriteOnlyProperties(schemaFromDescription as JSONSchemaType<unknown>),
-          resultBody
-        ),
+        passed: ajvStrict.validate(processedSchema, resultBody),
         message: ajvStrict.errors
-          ? printAjvErrors(
-              removeWriteOnlyProperties(schemaFromDescription as JSONSchemaType<unknown>),
-              resultBody,
-              ajvStrict.errors
-            )
+          ? printAjvErrors(processedSchema, resultBody, ajvStrict.errors)
           : '',
         severity: ctx.severity['SCHEMA_CHECK'],
       });