@google-cloud/promisify
Version:
A simple utility for promisifying functions and classes.
148 lines • 5.59 kB
JavaScript
;
/* eslint-disable prefer-rest-params */
Object.defineProperty(exports, "__esModule", { value: true });
exports.callbackifyAll = exports.callbackify = exports.promisifyAll = exports.promisify = void 0;
/**
* Wraps a callback style function to conditionally return a promise.
*
* @param {function} originalMethod - The method to promisify.
* @param {object=} options - Promise options.
* @param {boolean} options.singular - Resolve the promise with single arg instead of an array.
* @return {function} wrapped
*/
function promisify(originalMethod, options) {
if (originalMethod.promisified_) {
return originalMethod;
}
options = options || {};
const slice = Array.prototype.slice;
// tslint:disable-next-line:no-any
const wrapper = function () {
let last;
for (last = arguments.length - 1; last >= 0; last--) {
const arg = arguments[last];
if (typeof arg === 'undefined') {
continue; // skip trailing undefined.
}
if (typeof arg !== 'function') {
break; // non-callback last argument found.
}
return originalMethod.apply(this, arguments);
}
// peel trailing undefined.
const args = slice.call(arguments, 0, last + 1);
// tslint:disable-next-line:variable-name
let PromiseCtor = Promise;
// Because dedupe will likely create a single install of
// @google-cloud/common to be shared amongst all modules, we need to
// localize it at the Service level.
if (this && this.Promise) {
PromiseCtor = this.Promise;
}
return new PromiseCtor((resolve, reject) => {
// tslint:disable-next-line:no-any
args.push((...args) => {
const callbackArgs = slice.call(args);
const err = callbackArgs.shift();
if (err) {
return reject(err);
}
if (options.singular && callbackArgs.length === 1) {
resolve(callbackArgs[0]);
}
else {
resolve(callbackArgs);
}
});
originalMethod.apply(this, args);
});
};
wrapper.promisified_ = true;
return wrapper;
}
exports.promisify = promisify;
/**
* Promisifies certain Class methods. This will not promisify private or
* streaming methods.
*
* @param {module:common/service} Class - Service class.
* @param {object=} options - Configuration object.
*/
// tslint:disable-next-line:variable-name
function promisifyAll(Class, options) {
const exclude = (options && options.exclude) || [];
const ownPropertyNames = Object.getOwnPropertyNames(Class.prototype);
const methods = ownPropertyNames.filter(methodName => {
// clang-format off
return (!exclude.includes(methodName) &&
typeof Class.prototype[methodName] === 'function' && // is it a function?
!/(^_|(Stream|_)|promise$)|^constructor$/.test(methodName) // is it promisable?
);
// clang-format on
});
methods.forEach(methodName => {
const originalMethod = Class.prototype[methodName];
if (!originalMethod.promisified_) {
Class.prototype[methodName] = exports.promisify(originalMethod, options);
}
});
}
exports.promisifyAll = promisifyAll;
/**
* Wraps a promisy type function to conditionally call a callback function.
*
* @param {function} originalMethod - The method to callbackify.
* @param {object=} options - Callback options.
* @param {boolean} options.singular - Pass to the callback a single arg instead of an array.
* @return {function} wrapped
*/
function callbackify(originalMethod) {
if (originalMethod.callbackified_) {
return originalMethod;
}
// tslint:disable-next-line:no-any
const wrapper = function () {
if (typeof arguments[arguments.length - 1] !== 'function') {
return originalMethod.apply(this, arguments);
}
const cb = Array.prototype.pop.call(arguments);
originalMethod.apply(this, arguments).then(
// tslint:disable-next-line:no-any
(res) => {
res = Array.isArray(res) ? res : [res];
cb(null, ...res);
}, (err) => cb(err));
};
wrapper.callbackified_ = true;
return wrapper;
}
exports.callbackify = callbackify;
/**
* Callbackifies certain Class methods. This will not callbackify private or
* streaming methods.
*
* @param {module:common/service} Class - Service class.
* @param {object=} options - Configuration object.
*/
function callbackifyAll(
// tslint:disable-next-line:variable-name
Class, options) {
const exclude = (options && options.exclude) || [];
const ownPropertyNames = Object.getOwnPropertyNames(Class.prototype);
const methods = ownPropertyNames.filter(methodName => {
// clang-format off
return (!exclude.includes(methodName) &&
typeof Class.prototype[methodName] === 'function' && // is it a function?
!/^_|(Stream|_)|^constructor$/.test(methodName) // is it callbackifyable?
);
// clang-format on
});
methods.forEach(methodName => {
const originalMethod = Class.prototype[methodName];
if (!originalMethod.callbackified_) {
Class.prototype[methodName] = exports.callbackify(originalMethod);
}
});
}
exports.callbackifyAll = callbackifyAll;
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