GitbookIO/gitbook · error · Error

Expected schema of object to be provided: ${schema.type}

Error message

Expected schema of object to be provided: ${schema.type}

What it means

Thrown by inferDefaultInputValuesFromObjectJSONSchema in @gitbook/expr when the passed JSON schema is not of type 'object' or has no properties map. The function only produces a Record<string, InputValuesType> from an object schema's properties, so arrays, strings, or object schemas without properties are rejected.

Source

Thrown at packages/expr/src/input-values.ts:20

import { filterOutNullable } from './utils';

type InputValuesType =
    | null
    | string
    | number
    | boolean
    | { [key: string]: InputValuesType }
    | InputValuesType[];

/**
 * Infers a default inputValues object based on the JSON schema of an object.
 */
export function inferDefaultInputValuesFromObjectJSONSchema(
    schema: JSONSchema7
): Record<string, InputValuesType> {
    if (schema.type !== 'object' || !schema.properties) {
        throw new Error(`Expected schema of object to be provided: ${schema.type}`);
    }

    const result: Record<string, InputValuesType> = {};

    for (const [key, propertySchema] of Object.entries(schema.properties)) {
        if (typeof propertySchema === 'boolean') {
            continue;
        }

        result[key] = inferDefaultInputValueFromJSONSchema(propertySchema);
    }

    return result;
}

function inferDefaultInputValueFromJSONSchema(schema: JSONSchema7): InputValuesType {
    switch (schema.type) {
        case 'object':

View on GitHub (pinned to db67585ee2)

Solutions

1. Check schema.type === 'object' and schema.properties exists before calling; use inferDefaultInputValueFromJSONSchema for non-object schemas
2. Dereference $refs first so the concrete type/properties are present
3. If the input really is an array/scalar, switch to the single-value inference API

Example fix

// before
const values = inferDefaultInputValuesFromObjectJSONSchema(arraySchema); // type: 'array'

// after
const values =
    schema.type === 'object'
        ? inferDefaultInputValuesFromObjectJSONSchema(schema)
        : { value: inferDefaultInputValueFromJSONSchema(schema) };

const isObjectSchema = (s: JSONSchema7) => s.type === 'object' && !!s.properties;

function isObjectJSONSchema(schema: JSONSchema7): schema is JSONSchema7 & { type: 'object'; properties: Record<string, JSONSchema7Definition> } {
    return schema.type === 'object' && typeof schema.properties === 'object' && schema.properties !== null;
}

When it happens

Trigger: Calling defaultInputValues or inferDefaultInputValuesFromObjectJSONSchema with a schema whose type is 'array', 'string', 'number', or an object schema missing/empty properties (undefined properties triggers it too).

Common situations: Feeding a JSON Schema that describes an array or scalar instead of an object; schemas generated from tooling that omit properties; passing a $ref that hasn't been dereferenced so type/properties are absent; version changes in @gitbook/expr tightening schema requirements.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Unsupported schema type: ${schema.type}
• Invalid hex color provided: ${originalHex}
• Invalid nodes found when parsing
• Empty or invalid expression
• invalid

AI-assisted analysis of GitbookIO/gitbook@db67585ee2 (2026-08-28). Data as JSON: /api/errors/61b037b4d4ee9111. Report an issue: GitHub.