Telemetry: Add automigration errors

[yannbf]

Closes #

What I did

This PR attaches (sanitized, anonymized errors) to automigrations in the telemetry data, so we can detect patterns and use them to improve the Storybook upgrade experience.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli-storybook/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

Greptile Summary

This PR enhances Storybook's telemetry system by adding detailed error tracking for automigrations. The changes modify how error data is collected, stored, and transmitted during the upgrade process, specifically:

1. Introduces a new AutomigrationResult type that tracks both success statuses and error messages
2. Implements error sanitization using sanitizeError to ensure privacy when collecting error data
3. Updates the telemetry payload structure to include detailed error information
4. Modifies how failed automigrations are counted (now based on errors object length)

Confidence score: 5/5

1. This PR is extremely safe to merge as it only adds telemetry data collection and doesn't affect core functionality
2. The changes are well-structured, properly typed, and include appropriate error sanitization
3. The modified files (upgrade.ts and multi-project.ts) need careful review to ensure proper error handling

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☁️ Nx Cloud last updated this comment at 2025-07-22 13:46:26 UTC

[shilman]

Can we do it differently so that we have projectResults and projectErrors as peers? That way it's not a breaking change to the telemetry. Otherwise the new data won't be compatible with the old data and will be a pain in the neck.