sindresorhus / make-synchronous

Make an asynchronous function synchronous

make-synchronous

Make an asynchronous function synchronous

This is the wrong tool for most tasks! Prefer using async APIs whenever possible.

The benefit of this package over packages like deasync is that this one is not a native Node.js addon (which comes with a lot of problems). Instead, this package executes the given function synchronously in a subprocess.

This package works in Node.js only, not the browser.

Install

npm install make-synchronous

Usage

import makeSynchronous from 'make-synchronous';

const fn = makeSynchronous(async number => {
	const {default: delay} = await import('delay');

	await delay(100);

	return number * 2;
});

console.log(fn(2));
//=> 4

API

makeSynchronous(asyncFunction)

Returns a wrapped version of the given async function which executes synchronously. This means no other code will execute (not even async code) until the given async function is done.

The given function is executed in a subprocess, so you cannot use any variables/imports from outside the scope of the function. You can pass in arguments to the function. To import dependencies, use await import(…) in the function body.

It uses the V8 serialization API to transfer arguments, return values, errors between the subprocess and the current process. It supports most values, but not functions and symbols.

Related

• make-asynchronous - Make a synchronous function asynchronous by running it in a worker
• sleep-synchronously - Block the main thread for a given amount of time

make-synchronous's Issues

node version

is it possible to get this running with newer node versions?

I does not work with a current angular project.

Why not sleep-synchronously until the async call is done?

Why not sleep-synchronously until the async call is done?

Something like

const sleepSynchronously = require('sleep-synchronously');

function makeSynchronous(fn) {
  let done = false;
  let _result;
  let _error;

  (async () => {
    try {
      _result = await fn();
    } catch (error) {
      _error = error;
    }
    done = true;
  })();

  while (!done) {
    sleepSynchronously(100);
  }

  if (_error) {
    throw _error;
  }

  return _result;
}

Example doesn't work

Try running the example in https://npm.runkit.com/make-synchronous.

[feat] CJS

https://github.com/sindresorhus/make-synchronous#make-synchronous

This is the wrong tool for most tasks! Prefer using async APIs whenever possible.

• This is not a generic purpose package
• under the philosophy of special handling for special case

So, I think it might be better to have commonjs version of this package.

I think there are still a lot of real world cases need make-synchronous within CJS context, for example

• CJS package load ESM only package
• eslint/eslint#15394
• ...

So, as this is not a generic purpose package, I think it's worth to get CJS back.

• dual package
• or conditional exports
• or backport

BTW, what are the real world use case of make-synchronous within ESM context?

Use `worker_threads`

See https://github.com/rx-ts/synckit/blob/perf/make-synchronous/benchmarks/benchmark.txt

It's about 300x slower.

Can't execute mariadb function wrapper

I am trying to build a wrapper around a mariadb function, but calling it fails with error:
What am I doing wrong?

S:\Development\mariadb\node_modules\make-synchronous\index.js:61
throw error;
^

ReferenceError: ConnOptions is not defined
at createConnection ([stdin]:17:21)
at [stdin]:22:3
at [stdin]:27:6
at Script.runInThisContext (vm.js:120:18)
at Object.runInThisContext (vm.js:309:38)
at Object. ([stdin]-wrapper:10:26)
at Module._compile (internal/modules/cjs/loader.js:1015:30)
at evalScript (internal/process/execution.js:94:25)
at internal/main/eval_stdin.js:29:5
at Socket. (internal/process/execution.js:207:5)

Code:

const ms = require('make-synchronous');
const mariadb = require('mariadb');

function createConnection(opts) {
const fn = ms(mariadb.createConnection)
var conn = fn(opts)
return conn
}

var conn = createConnection({host:'localhost',user:'rudi',password:'secret'})

Accept `string` as function

The module already works with strings, only the types should be updated.

Probably type AsyncFunction = (...args: any[]) => Promise<unknown>; should be type AsyncFunction = ((...args: any[]) => Promise<unknown>;) | string

Passing parameter to first async call produces "No debugger available, can not send 'variables'"

I am calling an async function that calls a series of async functions.
First call in the series gives me the error "No debugger available...".
(createConnection)

Code:

function syncFunction(param) {
const ms = require('make-synchronous');
const fn = ms(a.asyncFunction(param))
return fn(param)
}

async function asyncFunction(param) {
var rows = []
const mariadb = require('mariadb');
var conn = await mariadb.createConnection({host: 'localhost', user: 'rudi', password:'***'});
try {
rows = await conn.query("SELECT 1 as val");
} catch (err) {
console.log('error')
throw err;
} finally {
await conn.destroy()
}
console.log(rows)
return rows
}

var res = syncFunction('example')
console.log(res)

Here is the output

const result = await ([object Promise])(...arguments_);
^^^^^^^

SyntaxError: Unexpected identifier
at new Script (vm.js:88:7)
at createScript (vm.js:261:10)
at Object.runInThisContext (vm.js:309:10)
at Object. (stdin-wrapper:10:26)
at Module._compile (internal/modules/cjs/loader.js:1015:30)
at evalScript (internal/process/execution.js:94:25)
at internal/main/eval_stdin.js:29:5
at Socket. (internal/process/execution.js:207:5)
at Socket.emit (events.js:326:22)
at endReadableNT (_stream_readable.js:1223:12)
end
[
{ val: 1 },
meta: [
ColumnDef {
_parse: [StringParser],
collation: [Collation],
columnLength: 1,
columnType: 3,
flags: 129,
scale: 0,
type: 'LONG'
}
]
]