fix: filter out $ref keys in bindings() to prevent undefined parser output

[q404365631]

Description

Fixes #877

When AsyncAPI documents contain message bindings with $ref references (e.g., {"$ref": "#/components/messageBindings/myBindings"}), the parser returns undefined instead of properly parsing the document.

Root Cause

The bindings() function in both v2/mixins.ts and v3/mixins.ts iterates over all entries of the bindings object using Object.entries(), including $ref keys. When a $ref key is present, it gets treated as a protocol name (like kafka, amqp, etc.), causing the Binding model to be created with invalid data, which ultimately causes the parser to crash or return undefined.

Fix

Filter out keys starting with $ (such as $ref) before processing binding entries, consistent with how the extensions() function filters keys using EXTENSION_REGEX.

Changes

• packages/parser/src/models/v3/mixins.ts: Added .filter(([key]) => !key.startsWith('$')) before .map() in the bindings() function
• packages/parser/src/models/v2/mixins.ts: Same fix applied to the v2 bindings() function

Testing

The fix ensures that:

1. Messages with $ref in bindings are parsed correctly instead of returning undefined
2. Normal protocol bindings (kafka, amqp, http, etc.) continue to work as expected
3. The $ref reference data is preserved in originalData for downstream processing

Reproduction

Before fix:

messages:
  myMessage:
    bindings:
      $ref: '#/components/messageBindings/myBindings'
    payload:
      type: object

Parser returns undefined for this message.

After fix:
Parser correctly creates the message model, with protocol bindings properly extracted (excluding the $ref key).

MICROGRANT

This PR resolves issue #877 which is part of the MICROGRANT Program 2026-06.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 64fb034

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

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

[github-actions]

Welcome to AsyncAPI. Thanks a lot for creating your first pull request. Please check out our contributors guide useful for opening a pull request.
Keep in mind there are also other channels you can use to interact with AsyncAPI community. For more details check out this issue.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[q404365631]

Hi! 👋 This PR fixes the issue where $ref keys in bindings cause the parser to return undefined. The fix filters out $ref keys before processing. Could someone please take a look? Thanks!