[DEP_WEBPACK_WATCH_WITHOUT_CALLBACK] error when using webpack serve with --watch flag

[benediktarnold]

Describe the bug

When running webpack serve with --watch the deprecation warning DEP_WEBPACK_WATCH_WITHOUT_CALLBACK shows up. Initially I thought it's just the same as #1918 but it's a different code path.

What is the current behavior?

When running node with --trace-deprecation this is the full deprecation stack:

10% building(node:54129) [DEP_WEBPACK_WATCH_WITHOUT_CALLBACK] DeprecationWarning: A 'callback' argument need to be provided to the 'webpack(options, callback)' function when the 'watch' option is set. There is no way to handle the 'watch' option without a callback.
    at webpack (/Users/ben/dev/playground/webpack-deprecation-warning/node_modules/webpack/lib/webpack.js:143:5)
    at f (/Users/ben/dev/playground/webpack-deprecation-warning/node_modules/webpack/lib/index.js:37:15)
    at WebpackCLI.createCompiler (/Users/ben/dev/playground/webpack-deprecation-warning/node_modules/webpack-cli/lib/webpack-cli.js:1337:24)
    at async Command.<anonymous> (/Users/ben/dev/playground/webpack-deprecation-warning/node_modules/@webpack-cli/serve/lib/index.js:65:30)
    at async Promise.all (index 1)
    at async Command.<anonymous> (/Users/ben/dev/playground/webpack-deprecation-warning/node_modules/webpack-cli/lib/webpack-cli.js:824:13)

To Reproduce

Steps to reproduce the behavior:

1. checkout https://github.com/benediktarnold/webpack-deprecation-warning
2. run npm install && npm start

Expected behavior

No deprecation warning

Please paste the results of webpack-cli info here, and mention other relevant information

System:
  OS: macOS 11.1
  CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
  Memory: 74.99 MB / 32.00 GB
Binaries:
  Node: 15.5.0 - /usr/local/bin/node
  Yarn: 1.22.10 - /usr/local/bin/yarn
  npm: 7.3.0 - /usr/local/bin/npm
Browsers:
  Chrome: 87.0.4280.141
  Firefox: 84.0.1
  Safari: 14.0.2
Packages:
  webpack: ^5.16.0 => 5.16.0
  webpack-cli: ^4.4.0 => 4.4.0
  webpack-dev-server: ^3.11.2 => 3.11.2
Global Packages:
  webpack: 5.11.1

Additional context

I think the root cause is in

webpack-cli/packages/serve/src/index.ts

Line 77 in 85648db

const compiler = await cli.createCompiler(webpackOptions);

where no callback is provided.

[alexander-akait]

You should not use --watch and serve together, it doesn't have sense, message is some misleading, but just remove it from your command

[benediktarnold]

That is indeed misleading since webpack serve --help mentions --watch as a possible option:

% webpack serve --help                                                                                                                                                                                                                                                                                                                  
Usage: webpack serve|s [options]

Run the webpack dev server.

Options:
  -c, --config <value...>     Provide path to a webpack configuration file e.g. ./webpack.config.js.
  --config-name <value...>    Name of the configuration to use.
  -m, --merge                 Merge two or more configurations using 'webpack-merge'.
  --env <value...>            Environment passed to the configuration when it is a function.
  --progress [value]          Print compilation progress during build.
  -j, --json [value]          Prints result as JSON or store it in a file.
  -d, --devtool <value>       Determine source maps to use.
  --no-devtool                Do not generate source maps.
  --entry <value...>          The entry point(s) of your application e.g. ./src/main.js.
  --mode <value>              Defines the mode to pass to webpack.
  --name <value>              Name of the configuration. Used when loading multiple configurations.
  -o, --output-path <value>   Output location of the file generated by webpack e.g. ./dist/.
  --stats [value]             It instructs webpack on how to treat the stats e.g. verbose.
  --no-stats                  Disable stats output.
  -t, --target <value...>     Sets the build target e.g. node.
  -w, --watch                 Watch for files changes.
  --no-watch                  Do not watch for file changes.

Could you please explain why it doesn't make sense to use serve with --watch? Thanks in advance!
Besides that, the help mentions --no-watch as well. Adding that option to the call has no effect at all and changed files are still compiled immediately.

[snitin315]

Could you please explain why it doesn't make sense to use serve with --watch? Thanks in advance!

serve already watches for changes.

[snitin315]

Maybe be we can add a warning here -

Do not use serve with --watch. serve already watches for changes.

[alexander-akait]

Could you please explain why it doesn't make sense to use serve with --watch? Thanks in advance!

It just has no effect.

Maybe be we can add a warning here -

Yes, warning will be great, and let's hide watch and --no-watch from help for serve and watch command

[snitin315]

I will send a PR

[benediktarnold]

Thanks for your help and your immediate PR! 👍