TypeScript users: Type Behavior change! items.vectors.default Now Returns number[] | number[][] - Type Error Fix

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If you’re encountering this TypeScript error after upgrading from weaviate-client v3.6.0 and above:

Type 'PrimitiveVectorType' is not assignable to type 'number[]'.
Type 'MultiVectorType' is not assignable to type 'number[]'.
Type 'number[]' is not assignable to type 'number'

New Type Definitions

In the upcoming release, items.vectors.default now returns PrimitiveVectorType which is essentially a union type number[] | number[][] instead of just number[]. This change introduces support for multi-vector scenarios while maintaining backward compatibility for single vectors.

export interface Vectors {
  [k: string]: PrimitiveVectorType;
}
export type PrimitiveVectorType = SingleVectorType | MultiVectorType;
export type SingleVectorType = number[];
export type MultiVectorType = number[][];

Problem Code Example

This code will now cause a TypeScript error:

const searchResults = await wikipediaCollection.query.nearText('women in the olympics', {
    autoLimit: 1,
    includeVector: true, 
    returnMetadata: ['distance'],
})

let myVec: number[]; 
for (const item of searchResults.objects) { 
    myVec = item.vectors.default; // ❌ Type error here
    console.log(myVec) 
}

Solutions

Use Type Assertions

If you know your data will always be a single vector:


let myVec: number[];
for (const item of searchResults.objects) { 
    myVec = item.vectors.default as number[]; // ✅ Type assertion
    console.log(myVec) 
}

If you know your data will always be a multi-vector:


let myVec: number[][];
for (const item of searchResults.objects) { 
    myVec = item.vectors.default as number[][]; // ✅ Type assertion
    console.log(myVec) 
}

:police_car_light: Optionally you can update your Type Annotations or use Type Guards.

Why This Change?

This breaking change enables support for multi-vector use cases while maintaining the existing API structure. The union type ensures type safety when working with both single vectors and multi-vector scenarios.

If you have questions about this change or need help with migration, please reply to this thread.

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