When does webpack cli comes into play - reactjs

Question

How is webpack-cli used in a project?
From what I understand, as soon as I enter npm run start on my bash terminal, webpack starts running the webpack config file where I have written rules to convert jsx to js using babel, scss/less to css (correct me if I'm wrong).
But where does webpack-cli comes into play in all this?

Answer 1

The webpack-dev-server package is responsible to serve the build over an http server that it creates for it. It also re-starts if you make any changes to the source code (when using the hot reload option).
On the other hand, the webpack-cli package is responsible for the build and bundle of the source files. So, webpack-dev-server has to run the webpack-cli.
So you've got to have both of the packages installed.
You can see kind of how it does that in here:
https://github.com/webpack/webpack-dev-server/blob/master/bin/webpack-dev-server.js
/** #type {CliOption} */
const cli = {
name: 'webpack-cli',
package: 'webpack-cli',
binName: 'webpack-cli',
installed: isInstalled('webpack-cli'),
url: 'https://github.com/webpack/webpack-cli',
preprocess() {
process.argv.splice(2, 0, 'serve');
},
};
// ...
const runCli = (cli) => {
if (cli.preprocess) {
cli.preprocess();
}
const path = require('path');
const pkgPath = require.resolve(`${cli.package}/package.json`);
// eslint-disable-next-line import/no-dynamic-require
const pkg = require(pkgPath);
// eslint-disable-next-line import/no-dynamic-require
require(path.resolve(path.dirname(pkgPath), pkg.bin[cli.binName]));
};
// ...
runCommand(packageManager, installOptions.concat(cli.package))
.then(() => {
runCli(cli);
})
.catch((error) => {
console.error(error);
process.exitCode = 1;
});
In webpack v5, that order kind of got reversed since you use webpack server, which is a webpack-cli call, to initiate the serve, that will call the webpack-dev-server package.
I'm not a webpack expert by any means, but I think this will help you to understand it better.