65 lines
1.3 KiB
JavaScript
65 lines
1.3 KiB
JavaScript
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'use strict'
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var slice = [].slice
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module.exports = wrap
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// Wrap `fn`.
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// Can be sync or async; return a promise, receive a completion handler, return
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// new values and errors.
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function wrap(fn, callback) {
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var invoked
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return wrapped
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function wrapped() {
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var params = slice.call(arguments, 0)
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var callback = fn.length > params.length
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var result
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if (callback) {
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params.push(done)
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}
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try {
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result = fn.apply(null, params)
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} catch (error) {
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// Well, this is quite the pickle.
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// `fn` received a callback and invoked it (thus continuing the pipeline),
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// but later also threw an error.
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// We’re not about to restart the pipeline again, so the only thing left
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// to do is to throw the thing instead.
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if (callback && invoked) {
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throw error
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}
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return done(error)
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}
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if (!callback) {
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if (result && typeof result.then === 'function') {
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result.then(then, done)
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} else if (result instanceof Error) {
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done(result)
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} else {
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then(result)
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}
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}
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}
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// Invoke `next`, only once.
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function done() {
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if (!invoked) {
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invoked = true
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callback.apply(null, arguments)
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}
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}
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// Invoke `done` with one value.
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// Tracks if an error is passed, too.
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function then(value) {
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done(null, value)
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}
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}
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