106 lines
2.0 KiB
JavaScript
106 lines
2.0 KiB
JavaScript
'use strict'
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/**
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* Module dependencies.
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*/
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const co = require('co')
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const compose = require('koa-compose')
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/**
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* Expose `convert()`.
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*/
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module.exports = convert
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/**
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* Convert Koa legacy generator-based middleware
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* to modern promise-based middleware.
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*
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*
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* @api public
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* */
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function convert (mw) {
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if (typeof mw !== 'function') {
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throw new TypeError('middleware must be a function')
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}
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// assume it's Promise-based middleware
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if (
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mw.constructor.name !== 'GeneratorFunction' &&
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mw.constructor.name !== 'AsyncGeneratorFunction'
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) {
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return mw
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}
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const converted = function (ctx, next) {
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return co.call(
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ctx,
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mw.call(
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ctx,
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(function * (next) { return yield next() })(next)
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))
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}
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converted._name = mw._name || mw.name
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return converted
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}
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/**
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* Convert and compose multiple middleware
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* (could mix legacy and modern ones)
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* and return modern promise middleware.
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*
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*
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* @api public
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* */
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// convert.compose(mw, mw, mw)
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// convert.compose([mw, mw, mw])
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convert.compose = function (arr) {
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if (!Array.isArray(arr)) {
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arr = Array.from(arguments)
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}
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return compose(arr.map(convert))
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}
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/**
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* Convert Koa modern promise-based middleware
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* to legacy generator-based middleware.
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*
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*
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* @api public
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* */
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convert.back = function (mw) {
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if (typeof mw !== 'function') {
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throw new TypeError('middleware must be a function')
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}
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// assume it's generator middleware
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if (mw.constructor.name === 'GeneratorFunction' || mw.constructor.name === 'AsyncGeneratorFunction') {
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return mw
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}
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const converted = function * (next) {
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const ctx = this
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let called = false
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yield mw(ctx, function () {
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if (called) {
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// guard against multiple next() calls
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// https://github.com/koajs/compose/blob/4e3e96baf58b817d71bd44a8c0d78bb42623aa95/index.js#L36
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throw new Error('next() called multiple times')
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}
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called = true
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return co.call(ctx, next)
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})
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}
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converted._name = mw._name || mw.name
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return converted
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}
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