---
stage: Create
group: Source Code
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# Merge request widget extensions **(FREE)**

> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/44616) in GitLab 13.6.

## Summary

Extensions in the merge request widget enable you to add new features
into the widget that match the existing design and interaction as other extensions.

## Usage

To use extensions you need to first create a new extension object to fetch the
data to render in the extension. See the example file in
`app/assets/javascripts/vue_merge_request_widget/extensions/issues.js` for a working example.

The basic object structure is as below:

```javascript
export default {
  name: '',
  props: [],
  computed: {
    summary() {},
    statusIcon() {},
  },
  methods: {
    fetchCollapsedData() {},
    fetchFullData() {},
  },
};
```

By following the same data structure, each extension can follow the same registering structure,
but each extension can manage its data sources.

After creating this structure you need to register it. Registering the extension can happen at any
point _after_ the widget has been created.

To register a extension the following can be done:

```javascript
// Import the register method
import { registerExtension } from '~/vue_merge_request_widget/components/extensions';

// Import the new extension
import issueExtension from '~/vue_merge_request_widget/extensions/issues';

// Register the imported extension
registerExtension(issueExtension);
```

## Fetching errors

If `fetchCollapsedData()` or `fetchFullData()` methods throw an error:

- The loading state of the extension is updated to `LOADING_STATES.collapsedError` and `LOADING_STATES.expandedError`
  respectively.
- The extensions header displays an error icon and updates the text to be either:
  - The text defined in `$options.i18n.error`.
  - "Failed to load" if `$options.i18n.error` is not defined.
- The error is sent to Sentry to log that it occurred.

To customise the error text, you need to add it to the `i18n` object in your extension:

```javascript
export default {
  //...
  i18n: {
    //...
    error: __('Your error text'),
  },
};
```