TL;DR

Yup has reached version 1.0, signifying a stable release after years of development and providing a more reliable validation (data correctness) experience.

Breaking

• Removed mixed() type. (Use .type('mixed') instead.)
• Removed nullable() and defined() methods. (Use .nullable() and .required() respectively.)

New

• Added support for specifying a custom message for each segment of a composite key. (Improves error clarity)
• Implemented test() schema method for custom validation logic. (Allows flexible validation rules)

Fixes Worth Knowing

• Fixed an issue where ref schemas weren’t correctly resolving in certain nested scenarios. (Improves complex form validation)

Before You Upgrade

• Update any code using mixed(), nullable(), or defined() to use the new equivalents as described in the Breaking Changes section.

TL;DR

Yup’s schema casting is changing in v1, and a migration path is now available to handle previously accepted patterns like nullable required fields.

Breaking

• Optionality Assertion: Yup v1 strictly enforces optionality during cast, disallowing patterns like string().nullable().required(). Use the new assert: 'ignore-optionality' option in cast for incremental upgrades.
• partial and lazy schemas: The order of operations for partial and lazy schemas has been adjusted for consistency, potentially impacting conditional schema behavior.

New

• Lazy Schema Improvements: Types and fixes have been implemented for lazy schemas (dynamic schemas) and deepPartial (partially defined objects).

Fixes Worth Knowing

• Fixed a bug where partial schemas weren’t correctly handling optionality with lazy schemas.
• Corrected typos in documentation and code comments.

Before You Upgrade

• Review your schemas for string().nullable().required() patterns and utilize the assert: 'ignore-optionality' option in cast during migration.

TL;DR

Yup now strictly enforces type casting, throwing errors instead of silently coercing invalid values to defaults, improving data validation reliability.

Breaking

• Type casting now throws errors for invalid types (data validation).
• cast option assert: false is required to retain previous silent coercion behavior.

Before You Upgrade

If you rely on Yup’s previous silent type coercion, explicitly set assert: false in your cast options to maintain existing behavior.