feat(rules): update operation-tag-defined rule

check for `tags` existence in `Operation` node`

.changeset/tasty-cougars-dress.md

@@ -0,0 +1,6 @@
+---
+"@redocly/openapi-core": patch
+"@redocly/cli": patch
+---
+
+Updated `operation-tag-defined` configurable rule.

packages/core/src/rules/common/__tests__/operation-tag-defined.test.ts

@@ -0,0 +1,68 @@
+import { outdent } from 'outdent';
+import { lintDocument } from '../../../lint';
+import { parseYamlToDocument, replaceSourceWithRef, makeConfig } from '../../../../__tests__/utils';
+import { BaseResolver } from '../../../resolve';
+
+describe('Oas3 operation-tag-defined', () => {
+  it('should not report on operation object if at least one tag is defined', async () => {
+    const document = parseYamlToDocument(
+      outdent`
+          openapi: 3.0.4
+          tags:
+            - name: a
+          paths:
+            /some:
+              get:
+                tags:
+                  - a
+        `,
+      'foobar.yaml'
+    );
+
+    const results = await lintDocument({
+      externalRefResolver: new BaseResolver(),
+      document,
+      config: await makeConfig({ rules: { 'operation-tag-defined': 'error' } }),
+    });
+
+    expect(replaceSourceWithRef(results)).toMatchInlineSnapshot(`[]`);
+  });
+
+  it('should report on operation object if no tags are defined', async () => {
+    const document = parseYamlToDocument(
+      outdent`
+      openapi: 3.0.4
+      tags:
+        - name: a
+      paths:
+        /some:
+          get:
+        `,
+      'foobar.yaml'
+    );
+
+    const results = await lintDocument({
+      externalRefResolver: new BaseResolver(),
+      document,
+      config: await makeConfig({ rules: { 'operation-tag-defined': 'error' } }),
+    });
+
+    expect(replaceSourceWithRef(results)).toMatchInlineSnapshot(`
+      [
+        {
+          "location": [
+            {
+              "pointer": "#/paths/~1some/get/tags",
+              "reportOnKey": true,
+              "source": "foobar.yaml",
+            },
+          ],
+          "message": "Operation tags should be defined",
+          "ruleId": "operation-tag-defined",
+          "severity": "error",
+          "suggest": [],
+        },
+      ]
+    `);
+  });
+});

packages/core/src/rules/common/operation-tag-defined.ts

@@ -11,6 +11,13 @@ export const OperationTagDefined: Oas3Rule | Oas2Rule = () => {
       definedTags = new Set((root.tags ?? []).map((t) => t.name));
     },
     Operation(operation: Oas2Operation | Oas3Operation, { report, location }: UserContext) {
+      if (!operation?.hasOwnProperty('tags')) {
+        report({
+          message: `Operation tags should be defined`,
+          location: location.child('tags').key(),
+        });
+        return;
+      }
       if (operation.tags) {
         for (let i = 0; i < operation.tags.length; i++) {
           if (!definedTags.has(operation.tags[i])) {