feat: Add ensureError utility for converting unknown values to error

[abretonc7s]

Summary

This utility already exists in metamask-mobile and is duplicated across different teams/codebases. It makes sense to have it published in @metamask/utils as a shared utility.

Currently, when catching errors in JavaScript/TypeScript, the caught value can be anything (unknown). The existing error utilities provide:

• Type guards: isErrorWithCode, isErrorWithMessage, isErrorWithStack
• Message extraction: getErrorMessage(error) → returns a string
• Error wrapping: wrapError(error, message) → creates new Error with cause link

However, there is no utility to guarantee an Error instance from an unknown caught value without wrapping it in a new Error.

This PR adds ensureError(error: unknown): Error which:

• Returns the original Error instance unchanged if already an Error
• Converts non-Error values to Error("Unknown error") with the original value preserved in cause

For adding context, developers can compose with wrapError: wrapError(ensureError(err), 'context')

Why this is needed

In mobile, we have many locations doing error instanceof Error ? error : new Error(error). This utility standardizes that pattern. External libraries and third-party SDKs sometimes throw non-Error values (undefined, strings, objects), and we need to convert them to proper Error instances for Sentry to process correctly.

Real example: METAMASK-MOBILE-5DKA - 10,675 occurrences affecting 429 users where HyperLiquid SDK throws undefined.

Key differences from wrapError:

Utility	Purpose	Output
getErrorMessage()	Extract message safely	string
wrapError()	Add context, create error chain	Error (new, with cause)
ensureError()	Guarantee Error instance	Error (original or converted)

• ensureError returns the original Error if already an Error (no wrapping)
• wrapError always creates a new Error with a cause chain

Implementation notes

• Uses direct property assignment for cause to preserve the original thrown value for debugging
• Simple type assertion avoids the need for polyfills or TypeScript ignores

Test plan

• Added comprehensive tests for all scenarios (Error instances, fs.promises errors, strings, objects, null, undefined)
• Tests verify Error instances are returned unchanged (preserving stack traces)
• Tests verify original value is preserved in cause
• All existing tests pass
• 100% code coverage maintained
• Linting passes
• Build succeeds

[Copilot]

Pull request overview

This PR adds a new ensureError utility function to the @metamask/utils package that guarantees an Error instance from unknown values without wrapping existing errors. This addresses a common need across MetaMask codebases where caught errors need to be converted to Error instances while preserving original errors unchanged.

Changes:

• Adds ensureError(error: unknown, context?: string): Error function that returns existing Error instances unchanged or converts other values to Error instances
• Provides comprehensive test coverage for all code paths including Error instances, fs.promises errors, primitives (strings, numbers), objects, and null/undefined
• Updates export snapshots in both index and node entry points

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/errors.ts	Implements the new ensureError function with proper type guards and message handling
src/errors.test.ts	Adds comprehensive test suite covering all scenarios including Error preservation, type conversions, and context handling
src/index.test.ts	Updates export snapshot to include ensureError in alphabetical order
src/node.test.ts	Updates export snapshot to include ensureError in alphabetical order

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[Gudahtt]

I had a couple of questions, but good idea to make this a shared utility. I've wanted this for a long time. The type checking/coercion in every single catch block is such a pain.

[cursor]

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

[Gudahtt]

Requesting changes due to disallowed @ts-ignore directives

Requested changes (ts-ignore removal) have been made

[Gudahtt]

LGTM!