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I tried to implement async/await in javascript staying closer to CPS form without the extra caching layers and state machines (without the promises) that normal

I tried to implement async/await in javascript staying closer to CPS form without the extra caching layers and state machines (without the promises) that normally wrap every async calls. https://www.npmjs.com/package/casync https://www.npmjs.com/package/casync I use it all the time. Except for the lack of language level tooling (that you get with promise wrapped async/await), it works quite well and it's faster than native async/await. I wish something like it would be integrated in the language.

dandanua 6y ago
Very cool! I was always wondering why a single-threaded language doesn't transform async/await into a "callback heaven" under the hood. It should be much easier than what Rust did to garbage collection.
- Twisol 6y ago
  Exceptions kind of muck with things, since you want to be able to establish handlers further up the stack. Compiling async/await to callbacks means also compiling exceptions down to a different mechanism, which makes it difficult to get a stack trace and so on.
  - BenoitEssiambre 6y ago
    Note that casync gives you somewhat ok stack traces (with language level support it could be better) for example: const {casync} = require('./casync.js'); let inner=casync(function*(next){ throw new Error("test err"); }); let outer=casync(function*(next){ yield inner(next); }); outer((err)=>{throw err;}); Gives you Error: test err at /home/benoit/Documents/casync/errorTest.js:4:8 at Generator.next (<anonymous>) at doNext (/home/benoit/Documents/casync/casync.js:26:12) at next (/home/benoit/Documents/casync/casync.js:44:5) at /home/benoit/Documents/casync/casync.js:49:3 at /home/benoit/Documents/casync/errorTest.js:8:8 at Generator.next (<anonymous>) at doNext (/home/benoit/Documents/casync/casync.js:26:12) at next (/home/benoit/Documents/casync/casync.js:44:5) at /home/benoit/Documents/casync/casync.js:49:3 If you skip the lines inside casync which are in most case irrelevant you get: Error: test err at /home/benoit/Documents/casync/errorTest.js:4:8 at /home/benoit/Documents/casync/errorTest.js:8:8

dandanua 6y ago

Very cool! I was always wondering why a single-threaded language doesn't transform async/await into a "callback heaven" under the hood. It should be much easier than what Rust did to garbage collection.

Twisol 6y ago
Exceptions kind of muck with things, since you want to be able to establish handlers further up the stack. Compiling async/await to callbacks means also compiling exceptions down to a different mechanism, which makes it difficult to get a stack trace and so on.
- BenoitEssiambre 6y ago
  Note that casync gives you somewhat ok stack traces (with language level support it could be better) for example: const {casync} = require('./casync.js'); let inner=casync(function*(next){ throw new Error("test err"); }); let outer=casync(function*(next){ yield inner(next); }); outer((err)=>{throw err;}); Gives you Error: test err at /home/benoit/Documents/casync/errorTest.js:4:8 at Generator.next (<anonymous>) at doNext (/home/benoit/Documents/casync/casync.js:26:12) at next (/home/benoit/Documents/casync/casync.js:44:5) at /home/benoit/Documents/casync/casync.js:49:3 at /home/benoit/Documents/casync/errorTest.js:8:8 at Generator.next (<anonymous>) at doNext (/home/benoit/Documents/casync/casync.js:26:12) at next (/home/benoit/Documents/casync/casync.js:44:5) at /home/benoit/Documents/casync/casync.js:49:3 If you skip the lines inside casync which are in most case irrelevant you get: Error: test err at /home/benoit/Documents/casync/errorTest.js:4:8 at /home/benoit/Documents/casync/errorTest.js:8:8