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mock.js
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mock.js
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'use strict';
const {
ArrayPrototypePush,
ArrayPrototypeSlice,
Error,
FunctionPrototypeCall,
ObjectDefineProperty,
ObjectGetOwnPropertyDescriptor,
ObjectGetPrototypeOf,
Proxy,
ReflectApply,
ReflectConstruct,
ReflectGet,
SafeMap,
} = primordials;
const {
codes: {
ERR_INVALID_ARG_TYPE,
ERR_INVALID_ARG_VALUE,
},
} = require('internal/errors');
const { kEmptyObject } = require('internal/util');
const {
validateBoolean,
validateFunction,
validateInteger,
validateObject,
} = require('internal/validators');
const { MockTimers } = require('internal/test_runner/mock/mock_timers');
function kDefaultFunction() {}
class MockFunctionContext {
#calls;
#mocks;
#implementation;
#restore;
#times;
constructor(implementation, restore, times) {
this.#calls = [];
this.#mocks = new SafeMap();
this.#implementation = implementation;
this.#restore = restore;
this.#times = times;
}
/**
* Gets an array of recorded calls made to the mock function.
* @returns {Array} An array of recorded calls.
*/
get calls() {
return ArrayPrototypeSlice(this.#calls, 0);
}
/**
* Retrieves the number of times the mock function has been called.
* @returns {number} The call count.
*/
callCount() {
return this.#calls.length;
}
/**
* Sets a new implementation for the mock function.
* @param {Function} implementation - The new implementation for the mock function.
*/
mockImplementation(implementation) {
validateFunction(implementation, 'implementation');
this.#implementation = implementation;
}
/**
* Replaces the implementation of the function only once.
* @param {Function} implementation - The substitute function.
* @param {number} [onCall] - The call index to be replaced.
*/
mockImplementationOnce(implementation, onCall) {
validateFunction(implementation, 'implementation');
const nextCall = this.#calls.length;
const call = onCall ?? nextCall;
validateInteger(call, 'onCall', nextCall);
this.#mocks.set(call, implementation);
}
/**
* Restores the original function that was mocked.
*/
restore() {
const { descriptor, object, original, methodName } = this.#restore;
if (typeof methodName === 'string') {
// This is an object method spy.
ObjectDefineProperty(object, methodName, descriptor);
} else {
// This is a bare function spy. There isn't much to do here but make
// the mock call the original function.
this.#implementation = original;
}
}
/**
* Resets the recorded calls to the mock function
*/
resetCalls() {
this.#calls = [];
}
/**
* Tracks a call made to the mock function.
* @param {object} call - The call details.
*/
trackCall(call) {
ArrayPrototypePush(this.#calls, call);
}
/**
* Gets the next implementation to use for the mock function.
* @returns {Function} The next implementation.
*/
nextImpl() {
const nextCall = this.#calls.length;
const mock = this.#mocks.get(nextCall);
const impl = mock ?? this.#implementation;
if (nextCall + 1 === this.#times) {
this.restore();
}
this.#mocks.delete(nextCall);
return impl;
}
}
const { nextImpl, restore, trackCall } = MockFunctionContext.prototype;
delete MockFunctionContext.prototype.trackCall;
delete MockFunctionContext.prototype.nextImpl;
class MockTracker {
#mocks = [];
#timers;
/**
* Returns the mock timers of this MockTracker instance.
* @returns {MockTimers} The mock timers instance.
*/
get timers() {
this.#timers ??= new MockTimers();
return this.#timers;
}
/**
* Creates a mock function tracker.
* @param {Function} [original] - The original function to be tracked.
* @param {Function} [implementation] - An optional replacement function for the original one.
* @param {object} [options] - Additional tracking options.
* @param {number} [options.times=Infinity] - The maximum number of times the mock function can be called.
* @returns {ProxyConstructor} The mock function tracker.
*/
fn(
original = function() {},
implementation = original,
options = kEmptyObject,
) {
if (original !== null && typeof original === 'object') {
options = original;
original = function() {};
implementation = original;
} else if (implementation !== null && typeof implementation === 'object') {
options = implementation;
implementation = original;
}
validateFunction(original, 'original');
validateFunction(implementation, 'implementation');
validateObject(options, 'options');
const { times = Infinity } = options;
validateTimes(times, 'options.times');
const ctx = new MockFunctionContext(implementation, { __proto__: null, original }, times);
return this.#setupMock(ctx, original);
}
/**
* Creates a method tracker for a specified object or function.
* @param {(object | Function)} objectOrFunction - The object or function containing the method to be tracked.
* @param {string} methodName - The name of the method to be tracked.
* @param {Function} [implementation] - An optional replacement function for the original method.
* @param {object} [options] - Additional tracking options.
* @param {boolean} [options.getter=false] - Indicates whether this is a getter method.
* @param {boolean} [options.setter=false] - Indicates whether this is a setter method.
* @param {number} [options.times=Infinity] - The maximum number of times the mock method can be called.
* @returns {ProxyConstructor} The mock method tracker.
*/
method(
objectOrFunction,
methodName,
implementation = kDefaultFunction,
options = kEmptyObject,
) {
validateStringOrSymbol(methodName, 'methodName');
if (typeof objectOrFunction !== 'function') {
validateObject(objectOrFunction, 'object');
}
if (implementation !== null && typeof implementation === 'object') {
options = implementation;
implementation = kDefaultFunction;
}
validateFunction(implementation, 'implementation');
validateObject(options, 'options');
const {
getter = false,
setter = false,
times = Infinity,
} = options;
validateBoolean(getter, 'options.getter');
validateBoolean(setter, 'options.setter');
validateTimes(times, 'options.times');
if (setter && getter) {
throw new ERR_INVALID_ARG_VALUE(
'options.setter', setter, "cannot be used with 'options.getter'",
);
}
const descriptor = findMethodOnPrototypeChain(objectOrFunction, methodName);
let original;
if (getter) {
original = descriptor?.get;
} else if (setter) {
original = descriptor?.set;
} else {
original = descriptor?.value;
}
if (typeof original !== 'function') {
throw new ERR_INVALID_ARG_VALUE(
'methodName', original, 'must be a method',
);
}
const restore = { __proto__: null, descriptor, object: objectOrFunction, methodName };
const impl = implementation === kDefaultFunction ?
original : implementation;
const ctx = new MockFunctionContext(impl, restore, times);
const mock = this.#setupMock(ctx, original);
const mockDescriptor = {
__proto__: null,
configurable: descriptor.configurable,
enumerable: descriptor.enumerable,
};
if (getter) {
mockDescriptor.get = mock;
mockDescriptor.set = descriptor.set;
} else if (setter) {
mockDescriptor.get = descriptor.get;
mockDescriptor.set = mock;
} else {
mockDescriptor.writable = descriptor.writable;
mockDescriptor.value = mock;
}
ObjectDefineProperty(objectOrFunction, methodName, mockDescriptor);
return mock;
}
/**
* Mocks a getter method of an object.
* This is a syntax sugar for the MockTracker.method with options.getter set to true
* @param {object} object - The target object.
* @param {string} methodName - The name of the getter method to be mocked.
* @param {Function} [implementation] - An optional replacement function for the targeted method.
* @param {object} [options] - Additional tracking options.
* @param {boolean} [options.getter=true] - Indicates whether this is a getter method.
* @param {boolean} [options.setter=false] - Indicates whether this is a setter method.
* @param {number} [options.times=Infinity] - The maximum number of times the mock method can be called.
* @returns {ProxyConstructor} The mock method tracker.
*/
getter(
object,
methodName,
implementation = kDefaultFunction,
options = kEmptyObject,
) {
if (implementation !== null && typeof implementation === 'object') {
options = implementation;
implementation = kDefaultFunction;
} else {
validateObject(options, 'options');
}
const { getter = true } = options;
if (getter === false) {
throw new ERR_INVALID_ARG_VALUE(
'options.getter', getter, 'cannot be false',
);
}
return this.method(object, methodName, implementation, {
__proto__: null,
...options,
getter,
});
}
/**
* Mocks a setter method of an object.
* This function is a syntax sugar for MockTracker.method with options.setter set to true.
* @param {object} object - The target object.
* @param {string} methodName - The setter method to be mocked.
* @param {Function} [implementation] - An optional replacement function for the targeted method.
* @param {object} [options] - Additional tracking options.
* @param {boolean} [options.getter=false] - Indicates whether this is a getter method.
* @param {boolean} [options.setter=true] - Indicates whether this is a setter method.
* @param {number} [options.times=Infinity] - The maximum number of times the mock method can be called.
* @returns {ProxyConstructor} The mock method tracker.
*/
setter(
object,
methodName,
implementation = kDefaultFunction,
options = kEmptyObject,
) {
if (implementation !== null && typeof implementation === 'object') {
options = implementation;
implementation = kDefaultFunction;
} else {
validateObject(options, 'options');
}
const { setter = true } = options;
if (setter === false) {
throw new ERR_INVALID_ARG_VALUE(
'options.setter', setter, 'cannot be false',
);
}
return this.method(object, methodName, implementation, {
__proto__: null,
...options,
setter,
});
}
/**
* Resets the mock tracker, restoring all mocks and clearing timers.
*/
reset() {
this.restoreAll();
this.#timers?.reset();
this.#mocks = [];
}
/**
* Restore all mocks created by this MockTracker instance.
*/
restoreAll() {
for (let i = 0; i < this.#mocks.length; i++) {
FunctionPrototypeCall(restore, this.#mocks[i]);
}
}
#setupMock(ctx, fnToMatch) {
const mock = new Proxy(fnToMatch, {
__proto__: null,
apply(_fn, thisArg, argList) {
const fn = FunctionPrototypeCall(nextImpl, ctx);
let result;
let error;
try {
result = ReflectApply(fn, thisArg, argList);
} catch (err) {
error = err;
throw err;
} finally {
FunctionPrototypeCall(trackCall, ctx, {
__proto__: null,
arguments: argList,
error,
result,
// eslint-disable-next-line no-restricted-syntax
stack: new Error(),
target: undefined,
this: thisArg,
});
}
return result;
},
construct(target, argList, newTarget) {
const realTarget = FunctionPrototypeCall(nextImpl, ctx);
let result;
let error;
try {
result = ReflectConstruct(realTarget, argList, newTarget);
} catch (err) {
error = err;
throw err;
} finally {
FunctionPrototypeCall(trackCall, ctx, {
__proto__: null,
arguments: argList,
error,
result,
// eslint-disable-next-line no-restricted-syntax
stack: new Error(),
target,
this: result,
});
}
return result;
},
get(target, property, receiver) {
if (property === 'mock') {
return ctx;
}
return ReflectGet(target, property, receiver);
},
});
ArrayPrototypePush(this.#mocks, ctx);
return mock;
}
}
function validateStringOrSymbol(value, name) {
if (typeof value !== 'string' && typeof value !== 'symbol') {
throw new ERR_INVALID_ARG_TYPE(name, ['string', 'symbol'], value);
}
}
function validateTimes(value, name) {
if (value === Infinity) {
return;
}
validateInteger(value, name, 1);
}
function findMethodOnPrototypeChain(instance, methodName) {
let host = instance;
let descriptor;
while (host !== null) {
descriptor = ObjectGetOwnPropertyDescriptor(host, methodName);
if (descriptor) {
break;
}
host = ObjectGetPrototypeOf(host);
}
return descriptor;
}
module.exports = { MockTracker };