v0.21.0: The Webpack 4 Release!

Webpack 4 and so much more 🎇! This is a huge release that contains some backwards-compatibility breaks or changes.

To upgrade, change your version constraint to ^0.21.0 and run yarn upgrade.

You may also need to make a few other changes if you're a Symfony user:

• composer require symfony/webpack-encore-bundle
• Replace your manual script and link tags with the new encore_entry_script_tags() and encore_entry_link_tags() functions from that bundle.

Highlights

• [BC BREAK] Webpack was upgraded to version 4. This includes a number of major
  and minor changes. The changes are listed below under the
  Webpack 4 Upgrade section.

• [DEPRECATION] You must now call either Encore.enableSingleRuntimeChunk()
  or Encore.disableSingleRuntimeChunk(): not calling either method is
  deprecated. The recommended setting is Encore.enableSingleRuntimeChunk().
  This will cause a new runtime.js file to be created, which must be included
  on your page with a script tag (before any other script tags for Encore
  JavaScript files). See the documentation above enableSingleRuntimeChunk() in
  index.js for more details.

• [BEHAVIOR CHANGE] Previously, without any config, Babel was
  configured to "transpile" (i.e. re-write) your JavaScript so
  that it was compatible with all browsers that currently have
  more than 1% of the market share. The new default behavior
  is a bit more aggressive, and may rewrite even more code to
  be compatible with even older browsers. The recommendation
  is to add a new browserslist key to your package.json file
  that specifies exactly what browsers you need to support. For
  example, to get the old configuration, add the following to
  package.json:

{
    "browserslist": "> 1%"
}

See the browserslist library
for a full description of all of the valid browser descriptions.

• Added a new copyFiles() method that is able to copy static files
  into your build directory and allows them to be versioned. #409
  thanks to @Lyrkan

• Introduced a new configureSplitChunks() method that can be
  used to further configure the optimizations.splitChunks configuration.

• A new entrypoints.json file is now always output. For expert
  use-cases, the optimizations.splitChunks.chunks configuration
  can be set via configureSplitChunks() to all. Then, you
  can write some custom server-side code to parse the entrypoints.js
  so that you know which script and link tags are needed for
  each entry.

• The "dynamic import" syntax is now supported out of the box
  because the @babel/plugin-syntax-dynamic-import babel plugin
  is always enabled. This allows you to do "Dynamic Imports"
  as described here: https://webpack.js.org/guides/code-splitting/#dynamic-imports

• A new "version check" system was added for optional dependencies.
  Now, when you install optional plugins to support a feature, if
  you are using an unsupported version, you will see a warning.
  "Package recommendation" errors (i.e. when you enable a feature
  but you are missing some packages) will also contain the version
  in the install string when necessary (e.g. yarn add foo@^2.0).

• Support was added handlebars-loader by calling enableHandlebarsLoader().
  #301 thanks to @ogiammetta

• Support was added for eslint-loader by calling enableEslintLoader().
  #243 thanks to @pinoniq

• The css-loader can now be configured by calling configureCssLoader().
  #335 thanks to @XWB

• It's now possible to control the exclude for Babel so that you can
  process certain node_modules packages through Babel - use
  the new second argument to configureBabel() - #401 thanks to
  @Lyrkan.

Webpack 4 Upgrade Details

• Node 7 is no longer supported. This is because the new
  mini-css-extract-plugin does not support it (and neither)
  does Yarn.

• For Preact, the necessary plugin the user needs to install
  changed from babel-plugin-transform-react-jsx to @babel/plugin-transform-react-jsx.

• The NamedModulesPlugin was removed.

• The babel-preset-env package (which was at version ^1.2.2) was
  removed in favor of @babel/preset-env.

• ExtractTextPlugin was removed and replaced with
  mini-css-extract-plugin. Accordingly, extractTextPluginOptionsCallback()
  was removed.

• Support for CoffeeScript was entirely removed.

• Actual lang="sass" no longer works for Vue. However, lang="scss"
  continues to work fine.

• uglifyjs-webpack-plugin was replaced by terser-webpack-plugin.
  If you're using configureUglifyJsPlugin(), please switch to
  configureTerserPlugin() instead.