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86 lines
2.7 KiB
86 lines
2.7 KiB
3 years ago
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'use strict';
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/*
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* cls-bluebird
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* Function to shim `Promise.coroutine`
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*
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* Works by binding the `.next()` and `.throw()` methods of generator to CLS context
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* at time when coroutine is executed.
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*
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* In bluebird v3.x, running the coroutine internally calls `.lastly()` if cancellation is enabled.
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* To prevent unnecessary binding of the `.lastly()` callback to CLS context, this patch
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* temporarily disables the patch on `Promise.prototype.lastly`.
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* NB This patch could break if bluebird internals change, but this is covered by the tests.
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*/
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// Modules
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var shimmer = require('shimmer');
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// Exports
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/**
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* Patch `Promise.coroutine` or `Promise.spawn` to maintain current CLS context after all `yield` statements.
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*
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* @param {string} methodName - method name (either 'coroutine' or 'spawn')
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* @param {Function} Promise - Bluebird Promise constructor to patch
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* @param {Object} ns - CLS namespace to bind callbacks to
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* @returns {undefined}
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*/
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module.exports = function(methodName, Promise, ns, v3) {
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var lastlyPatched = Promise.prototype.lastly,
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lastlyOriginal = Promise.prototype.lastly.__original;
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// Patch method
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shimmer.wrap(Promise, methodName, function(original) {
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return function(generatorFunction, options) {
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// NB If `generatorFunction` is not a function, do not alter it.
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// Pass value directly to bluebird which will throw an error.
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if (typeof generatorFunction === 'function') {
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// Create proxy generator function
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var generatorFunctionOriginal = generatorFunction;
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generatorFunction = function() {
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// Create generator from generator function
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var generator = generatorFunctionOriginal.apply(this, arguments);
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// Bind `.next()`, '.throw()' and `.return()` to current CLS context.
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// NB CLS context is from when coroutine is called, not when created.
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['next', 'throw', 'return'].forEach(function(name) {
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if (typeof generator[name] === 'function') generator[name] = ns.bind(generator[name]);
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});
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return generator;
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};
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}
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// Temporarily remove patch from `Promise.prototype.lastly` in bluebird v3
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// to avoid unnecessary binding to CLS context.
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var self = this;
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if (methodName === 'spawn' && v3) {
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return tempPatchLastly(function() {
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return original.call(self, generatorFunction, options);
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});
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}
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var fn = original.call(this, generatorFunction, options);
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if (methodName === 'coroutine' && v3) {
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return function() {
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var self = this, args = arguments;
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return tempPatchLastly(function() {
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return fn.apply(self, args);
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});
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};
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}
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return fn;
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};
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});
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function tempPatchLastly(fn) {
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Promise.prototype.lastly = lastlyOriginal;
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var res = fn();
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Promise.prototype.lastly = lastlyPatched;
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return res;
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}
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};
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