--debug-webpack     Display final webpack configurations for debugging purposes

❯ npx build-storybook --debug-webpack
info @storybook/react v6.3.4
info 
info => Cleaning outputDir: /repo/storybook-static
info => Loading presets
info => Compiling preview..
info => Loading 1 config file in "/repo/.storybook"
info => Loading 9 other files in "/repo/.storybook"
info => Adding stories defined in "/repo/.storybook/main.js"
info => Using implicit CSS loaders
info => Using default Webpack4 setup
10% building 1/1 modules 0 active(node:41651) DeprecationWarning: Default PostCSS plugins are deprecated. When switching to '@storybook/addon-postcss',
you will need to add your own plugins, such as 'postcss-flexbugs-fixes' and 'autoprefixer'.

See https://github.com/storybookjs/storybook/blob/next/MIGRATION.md#deprecated-default-postcss-plugins for details.
(Use `node --trace-deprecation ...` to show where the warning was created)
info => Preview built (16 s)
WARN asset size limit: The following asset(s) exceed the recommended size limit (244 KiB).
WARN This can impact web performance.
WARN Assets: 
WARN   vendors~main.9bba21ad.iframe.bundle.js (3.29 MiB)
WARN entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.
WARN Entrypoints:
WARN   main (3.34 MiB)
WARN       runtime~main.d69e7d63.iframe.bundle.js
WARN       vendors~main.9bba21ad.iframe.bundle.js
WARN       main.36ab2da7.iframe.bundle.js
WARN 
info => Output directory: /repo/storybook-static**To Reproduce**


> npx sb@next repro

> cd reprodir

> npx build-storybook --help
Usage: build-storybook [options]

Options:
  -V, --version                     output the version number
  -s, --static-dir <dir-names>      Directory where to load static files from
  -o, --output-dir <dir-name>       Directory where to store built files
  -c, --config-dir <dir-name>       Directory where to load Storybook configurations from
  -w, --watch                       Enable watch mode
  --quiet                           Suppress verbose build output
  --loglevel <level>                Control level of logging during build
  --no-dll                          Do not use dll reference (no-op)
  --docs-dll                        Use Docs dll reference (legacy)
  --ui-dll                          Use UI dll reference (legacy)
  --debug-webpack                   Display final webpack configurations for debugging purposes
  --webpack-stats-json [directory]  Write Webpack Stats JSON to disk
  --preview-url <string>            Disables the default storybook preview and lets your use your own
  --force-build-preview             Build the preview iframe even if you are using --preview-url
  --docs                            Build a documentation-only site using addon-docs
  --modern                          Use modern browser modules
  -h, --help                        display help for command

> npx build-storybook --debug-webpack
info @storybook/react v6.4.0-alpha.17
info
info => Cleaning outputDir: /private/tmp/reprodir/storybook-static
info => Loading presets
info => Compiling preview..
info => Loading 1 config file in "/private/tmp/reprodir/.storybook"
info => Loading 9 other files in "/private/tmp/reprodir/.storybook"
info => Adding stories defined in "/private/tmp/reprodir/.storybook/main.js"
info => Using implicit CSS loaders
info => Using default Webpack4 setup
10% building 1/1 modules 0 active(node:42567) DeprecationWarning: Default PostCSS plugins are deprecated. When switching to '@storybook/addon-postcss',
you will need to add your own plugins, such as 'postcss-flexbugs-fixes' and 'autoprefixer'.

See https://github.com/storybookjs/storybook/blob/next/MIGRATION.md#deprecated-default-postcss-plugins for details.
(Use `node --trace-deprecation ...` to show where the warning was created)
info => Preview built (13 s)
WARN asset size limit: The following asset(s) exceed the recommended size limit (244 KiB).
WARN This can impact web performance.
WARN Assets:
WARN   vendors~main.2e20dc6c.iframe.bundle.js (1.96 MiB)
WARN entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.
WARN Entrypoints:
WARN   main (2 MiB)
WARN       runtime~main.cdb6c1c3.iframe.bundle.js
WARN       vendors~main.2e20dc6c.iframe.bundle.js
WARN       main.b83cef95.iframe.bundle.js
WARN
info => Output directory: /private/tmp/reprodir/storybook-static**System**

Environment Info:

  System:
    OS: macOS 11.4
    CPU: (8) x64 Intel(R) Core(TM) i5-1038NG7 CPU @ 2.00GHz
  Binaries:
    Node: 16.3.0 - /usr/local/bin/node
    Yarn: 2.4.2 - /usr/local/bin/yarn
    npm: 7.15.1 - /usr/local/bin/npm
  Browsers:
    Firefox: 89.0
    Safari: 14.1.1
  npmPackages:
    @storybook/addon-actions: ^6.4.0-alpha.17 => 6.4.0-alpha.17
    @storybook/addon-docs: ^6.4.0-alpha.17 => 6.4.0-alpha.17
    @storybook/addon-essentials: ^6.4.0-alpha.17 => 6.4.0-alpha.17
    @storybook/addon-links: ^6.4.0-alpha.17 => 6.4.0-alpha.17
    @storybook/react: ^6.4.0-alpha.17 => 6.4.0-alpha.17