ow/dist/utils/generate-argument-error-message.js

Function argument validation for humans

/**
Generates a complete message from all errors generated by predicates.

@param errors - The errors generated by the predicates.
@param isAny - If this function is called from the any argument.
@hidden
*/
export const generateArgumentErrorMessage = (errors, isAny = false) => {
    const message = [];
    const errorArray = [...errors.entries()];
    const anyErrorWithoutOneItemOnly = errorArray.some(([, array]) => array.size !== 1);
    // If only one error "key" is present, enumerate all of those errors only.
    if (errorArray.length === 1) {
        const [, returnedErrors] = errorArray[0];
        if (!isAny && returnedErrors.size === 1) {
            const [errorMessage] = returnedErrors;
            return errorMessage;
        }
        for (const entry of returnedErrors) {
            message.push(`${isAny ? '  - ' : ''}${entry}`);
        }
        return message.join('\n');
    }
    // If every predicate returns just one error, enumerate them as is.
    if (!anyErrorWithoutOneItemOnly) {
        return errorArray.map(([, [item]]) => `  - ${item}`).join('\n');
    }
    // Else, iterate through all the errors and enumerate them.
    for (const [key, value] of errorArray) {
        message.push(`Errors from the "${key}" predicate:`);
        for (const entry of value) {
            message.push(`  - ${entry}`);
        }
    }
    return message.join('\n');
};