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predicate.ts
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predicate.ts
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import is from '@sindresorhus/is';
import {ArgumentError} from '../argument-error';
import {not} from '../operators/not';
import {BasePredicate, testSymbol} from './base-predicate';
import {Main} from '..';
import {generateArgumentErrorMessage} from '../utils/generate-argument-error-message';
/**
Function executed when the provided validation fails.
@param value - The tested value.
@param label - Label of the tested value.
@returns {string} - The actual error message.
*/
export type ValidatorMessageBuilder<T> = (value: T, label?: string) => string;
/**
@hidden
*/
export interface Validator<T> {
message(value: T, label?: string, result?: any): string;
validator(value: T): unknown;
/**
Provide custom message used by `not` operator.
When absent, the return value of `message()` is used and 'not' is inserted after the first 'to', e.g. `Expected 'smth' to be empty` -> `Expected 'smth' to not be empty`.
*/
negatedMessage?(value: T, label: string): string;
}
/**
@hidden
*/
export interface PredicateOptions {
optional?: boolean;
}
/**
@hidden
*/
export interface Context<T = unknown> extends PredicateOptions {
validators: Array<Validator<T>>;
}
/**
@hidden
*/
export const validatorSymbol = Symbol('validators');
export type CustomValidator<T> = (value: T) => {
/**
Should be `true` if the validation is correct.
*/
validator: boolean;
/**
The error message which should be shown if the `validator` is `false`. Or a error function which returns the error message and accepts the label as first argument.
*/
message: string | ((label: string) => string);
};
/**
@hidden
*/
export class Predicate<T = unknown> implements BasePredicate<T> {
private readonly context: Context<T> = {
validators: []
};
constructor(
private readonly type: string,
private readonly options: PredicateOptions = {}
) {
this.context = {
...this.context,
...this.options
};
const typeString = this.type.charAt(0).toLowerCase() + this.type.slice(1);
this.addValidator({
message: (value, label) => {
// We do not include type in this label as we do for other messages, because it would be redundant.
const label_ = label?.slice(this.type.length + 1);
// eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
return `Expected ${label_ || 'argument'} to be of type \`${this.type}\` but received type \`${is(value)}\``;
},
validator: value => (is as any)[typeString](value)
});
}
/**
@hidden
*/
[testSymbol](value: T, main: Main, label: string | Function): asserts value is T {
// Create a map of labels -> received errors.
const errors = new Map<string, Set<string>>();
for (const {validator, message} of this.context.validators) {
if (this.options.optional === true && value === undefined) {
continue;
}
let result: unknown;
try {
result = validator(value);
} catch (error: unknown) {
// Any errors caught means validators couldn't process the input.
result = error;
}
if (result === true) {
continue;
}
const label2 = is.function_(label) ? label() : label;
const label_ = label2 ?
`${this.type} \`${label2}\`` :
this.type;
const mapKey = label2 || this.type;
// Get the current errors encountered for this label.
const currentErrors = errors.get(mapKey);
// Pre-generate the error message that will be reported to the user.
const errorMessage = message(value, label_, result);
// If we already have any errors for this label.
if (currentErrors) {
// If we don't already have this error logged, add it.
currentErrors.add(errorMessage);
} else {
// Set this label and error in the full map.
errors.set(mapKey, new Set([errorMessage]));
}
}
// If we have any errors to report, throw.
if (errors.size > 0) {
// Generate the `error.message` property.
const message = generateArgumentErrorMessage(errors);
throw new ArgumentError(message, main, errors);
}
}
/**
@hidden
*/
get [validatorSymbol](): Array<Validator<T>> {
return this.context.validators;
}
/**
Invert the following validators.
*/
get not(): this {
return not(this) as this;
}
/**
Test if the value matches a custom validation function. The validation function should return an object containing a `validator` and `message`. If the `validator` is `false`, the validation fails and the `message` will be used as error message. If the `message` is a function, the function is invoked with the `label` as argument to let you further customize the error message.
@param customValidator - Custom validation function.
*/
validate(customValidator: CustomValidator<T>): this {
return this.addValidator({
message: (_, label, error) => typeof error === 'string' ?
`(${label}) ${error}` :
error(label),
validator: value => {
const {message, validator} = customValidator(value);
if (validator) {
return true;
}
return message;
}
});
}
/**
Test if the value matches a custom validation function. The validation function should return `true` if the value passes the function. If the function either returns `false` or a string, the function fails and the string will be used as error message.
@param validator - Validation function.
*/
is(validator: (value: T) => boolean | string): this {
return this.addValidator({
message: (value, label, error) => (error ?
`(${label}) ${error}` :
`Expected ${label} \`${value}\` to pass custom validation function`
),
validator
});
}
/**
Provide a new error message to be thrown when the validation fails.
@param newMessage - Either a string containing the new message or a function returning the new message.
@example
```
ow('🌈', 'unicorn', ow.string.equals('🦄').message('Expected unicorn, got rainbow'));
//=> ArgumentError: Expected unicorn, got rainbow
```
@example
```
ow('🌈', ow.string.minLength(5).message((value, label) => `Expected ${label}, to have a minimum length of 5, got \`${value}\``));
//=> ArgumentError: Expected string, to be have a minimum length of 5, got `🌈`
```
*/
message(newMessage: string | ValidatorMessageBuilder<T>): this {
const {validators} = this.context;
validators[validators.length - 1]!.message = (value, label): string => {
if (typeof newMessage === 'function') {
return newMessage(value, label);
}
return newMessage;
};
return this;
}
/**
Register a new validator.
@param validator - Validator to register.
*/
addValidator(validator: Validator<T>): this {
this.context.validators.push(validator);
return this;
}
}