How to execute custom asynchronous manipulations inside Gulp `.pipe`? - gulp

Question

gulp-intercept allows synchronous manipulations with file:
import gulpIntercept from "gulp-intercept";
import VinylFile from "vinyl";
// ...
.pipe(gulpIntercept((compiledHtmlFile: VinylFile): VinylFile => {
doSomethingSyncWith(compiledHtmlFile)
return compiledHtmlFile;
}))
// ...
But I am not sure it will not work for asynchronous manipulations because it has not been documented. Well, when this package was development, maybe even Promises did not exist in ECMAScript.
import gulpIntercept from "gulp-intercept";
import VinylFile from "vinyl";
// ...
// I suppose it will not work.
.pipe(gulpIntercept(async (compiledHtmlFile: VinylFile): VinylFile => {
// does "gulp.pipe" really will wait until it ends?
await doSomethingAsyncWith(compiledHtmlFile)
return compiledHtmlFile;
}))
// ...
There is should be another gulp plugin for for asynchronous manipulations instead. Would you please to teach me it?

Answer 1

Looks like the library you are using doesn't support async functions as an input (as you already said!) but you don't need to use the library at all you can use event-stream and map your function and call callback at the end in following manner:
import VinylFile from "vinyl";
const es = require('event-stream');
const gulp = require('gulp');
// ..
.pipe(
es.map(
async (compiledHtmlFile: VinylFile, callback: any): VinylFile => {
// "gulp.pipe" will really wait until it ends!!!
await doSomethingAsyncWith(compiledHtmlFile);
callback(null, compiledHtmlFile);
}
)
)
// ...
or use with then:
// ..
.pipe(
es.map(
async (compiledHtmlFile: VinylFile, callback: any): VinylFile => {
doSomethingAsyncWith(compiledHtmlFile)
.then(() => {
callback(null, compiledHtmlFile);
});
}
)
)
// ...