Comments (6)
You have to either await
or return
next()
. In this case it looks like you should return
since middleware don't do anything after calling next
from compose.
OK , I change my example code ~
const compose = require('koa-compose');
const middleware = [
function (ctx, next) {
// ctx.step1 = true;
ctx.steps = [];
ctx.steps.push(1);
return next();
},
function (ctx, next) {
next();
ctx.steps.push(4);
},
function (ctx, next) {
next();
a = b;
ctx.steps.push(3);
},
function (ctx, next) {
next();
ctx.steps.push(2);
}
];
const ctx = {};
compose(middleware)(ctx).then(() => {
console.log('success', ctx);
}).catch((err) => {
console.log('err', err.stack);
});
If I either return next(), it seems Unreasonable~
from compose.
No exception is going to be thrown with the code above as far as I can tell so the catch at the end won't be called.
However, the middleware need to return next()
for the execution to go down the stack. Middleware are work like a chain of promises. A call to next()
returns a promise that will resolve when the execution has gone down the stack and back up to the given middleware's position again. If you don't return the promise, the stack is traversed in reverse from that point and won't wait for the rest of the chain.
from compose.
Yes , I try to change compose core code~ like this
return function (context, next) {
let index = -1
return dispatch(0)
function dispatch (i) {
if (i <= index) return Promise.reject(new Error('next() called multiple times'))
index = i
let fn = middleware[i]
if (i === middleware.length) fn = next
if (!fn) return Promise.resolve()
try {
// return Promise.resolve(fn(context, function next () {
// return dispatch(i + 1)
// }))
return new Promise((resolve,reject)=>{
fn(context,()=>{resolve(dispatch(i+1));});
})
} catch (err) {
return Promise.reject(err)
}
}
}
I try to keep the promise chain, but can't pass npm test
from compose.
@cavacn You need to return promise in all middleware calling next()
. That's the design of it. Not sure why you're working against it? What are you trying to solve?
from compose.
@fl0w @danwkennedy thanks, Ok , I got it ~
from compose.
Related Issues (20)
- If `fn` is an asynchronous function, this `try catch` will be useless οΌ HOT 2
- I found that some code in the source code like `Promise.reject(),Promise.resolve()` seems redundant HOT 1
- Behavior changes on 4.2.0 HOT 5
- Add debug logs before and after each middleware executes HOT 1
- License is not included
- I donβt understand how the error is thrown when I find that next is called repeatedly. HOT 2
- Why use Promise.resolve() to wrap the execution results of each middleware? HOT 2
- Abnormal middleware errors occurred and KOA could not catch error events. How about the following changes
- [Question/Proposal] Sync/Async execution HOT 1
- Set default branch to next, default npm release to v3 HOT 1
- guard against unhandled next()s in development HOT 15
- Reorganize tests, and switch to Jest HOT 5
- when i use koa-compose with koa-router, koa-router does not work. HOT 6
- [Q&A] About Promise in the source code. HOT 1
- Outdated yield tests
- Can't use destructuring with async await. HOT 2
- Unit test to verify if it handles wrapped non-async functions is wrong. HOT 1
- Control passed to handler before completing middleware chain HOT 4
- Multiple next with non async function HOT 7
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from compose.