fix: resolve discriminator defaultMapping into components schemas when bundling

[tatomyr]

What/Why/How?

Fixed an issue where discriminator defaultMapping was not resolved when bundling.

Reference

Testing

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Check yourself

• This PR follows the contributing guide
• All new/updated code is covered by tests
• Core code changed? - Tested with other Redocly products (internal contributions only)
• New package installed? - Tested in different environments (browser/node)
• Documentation update has been considered

Security

• The security impact of the change has been considered
• Code follows company security practices and guidelines

---

Note

Low Risk
Low risk: change is scoped to OAS3 bundling behavior for discriminator.defaultMapping and is covered by new unit and e2e tests, with minimal surface area outside bundling.

Overview
Fixes bundling so OAS3 discriminator.defaultMapping is treated like discriminator.mapping: mapping-like values are now resolved and saved into #/components/schemas/... instead of being left as an unresolved string.

Adds regression coverage via a new unit test for component-name mappings and a new OAS 3.2 e2e fixture/snapshot verifying defaultMapping to an external schema is rewritten to an internal component ref.

^{Reviewed by Cursor Bugbot for commit daa0ca6. Bugbot is set up for automated code reviews on this repo. Configure here.}

[changeset-bot]

🦋 Changeset detected

Latest commit: daa0ca6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@redocly/openapi-core	Patch
@redocly/cli	Patch
@redocly/respect-core	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	79.93% (🎯 79%)	6727 / 8416
🔵	Statements	79.36% (🎯 79%)	6965 / 8776
🔵	Functions	83.1% (🎯 82%)	1367 / 1645
🔵	Branches	71.55% (🎯 71%)	4566 / 6381

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
packages/core/src/bundle/bundle-visitor.ts	64.75%	61.06%	100%	64.75%	30, 34-42, 49-57, 64, 73, 81, 86-107, 172-184, 201-202, 219-225, 236-237, 274

Generated in workflow #9444 for commit daa0ca6 by the Vitest Coverage Report Action

[github-actions]

CLI Version	Mean Time ± Std Dev (s)	Relative Performance (Lower is Faster)
cli-latest	3.253s ± 0.047s	▓ 1.01x
cli-next	3.228s ± 0.008s	▓ 1.00x (Fastest)

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Missing isMappingRef check for defaultMapping resolution
  • Added an isMappingRef guard before resolving defaultMapping and covered the plain schema-name case with a unit test so valid OAS 3.2 documents no longer report unresolved refs.

Or push these changes by commenting:

@cursor push 49f3370f76

Preview (49f3370f76)

diff --git a/packages/core/src/__tests__/bundle.test.ts b/packages/core/src/__tests__/bundle.test.ts
--- a/packages/core/src/__tests__/bundle.test.ts
+++ b/packages/core/src/__tests__/bundle.test.ts
@@ -302,6 +302,36 @@
     expect(problems).toHaveLength(0);
   });
 
+  it('should not resolve discriminator defaultMapping schema names (OAS 3.2)', async () => {
+    const document = outdent`
+      openapi: 3.2.0
+      paths: {}
+      components:
+        schemas:
+          Pet:
+            type: object
+            discriminator:
+              propertyName: kind
+              defaultMapping: Cat
+          Cat:
+            type: object
+            properties:
+              kind:
+                type: string
+    `;
+
+    const {
+      bundle: { parsed },
+      problems,
+    } = await bundleFromString({
+      source: document,
+      config: await createConfig({}),
+    });
+
+    expect(problems).toHaveLength(0);
+    expect((parsed as any).components.schemas.Pet.discriminator.defaultMapping).toBe('Cat');
+  });
+
   it('should pull hosted schema', async () => {
     const { bundle: res, problems } = await bundle({
       config: await createConfig({}),

diff --git a/packages/core/src/bundle/bundle-visitor.ts b/packages/core/src/bundle/bundle-visitor.ts
--- a/packages/core/src/bundle/bundle-visitor.ts
+++ b/packages/core/src/bundle/bundle-visitor.ts
@@ -2,6 +2,7 @@
 import { type SpecMajorVersion } from '../oas-types.js';
 import {
   isAbsoluteUrl,
+  isMappingRef,
   replaceRef,
   isExternalValue,
   isRef,
@@ -208,7 +209,12 @@
     const componentType = mapTypeToComponent('Schema', version)!;
     visitor.Discriminator = {
       leave(discriminator: Oas3Discriminator, ctx: UserContext) {
-        if (typeof discriminator.defaultMapping !== 'string') return;
+        if (
+          typeof discriminator.defaultMapping !== 'string' ||
+          !isMappingRef(discriminator.defaultMapping)
+        ) {
+          return;
+        }
 
         const resolved = ctx.resolve({ $ref: discriminator.defaultMapping });
         if (!resolved.location || resolved.node === undefined) {

_{This Bugbot Autofix run was free. To enable autofix for future PRs, go to the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit a94bfe2. Configure here.}

[github-actions]

📦 A new experimental 🧪 version v0.0.0-snapshot.1776177415 of Redocly CLI has been published for testing.

Install with NPM:

npm install @redocly/cli@0.0.0-snapshot.1776177415
# or
npm install @redocly/openapi-core@0.0.0-snapshot.1776177415
# or
npm install @redocly/respect-core@0.0.0-snapshot.1776177415

⚠️ Note: This is a development build and may contain unstable features.