- Read the error message carefully. The error message will tell you the precise key value that is not matching what Webpack expects.
- Put a
debugger
statement in your Webpack configuration and runbin/webpack --debug-webpacker
. If you have a node debugger installed, you'll see the Chrome debugger for your webpack config. For example, install the Chrome extension NiM and set the option for the dev tools to open automatically. For more details on debugging, see the official Webpack docs on debugging - Any arguments that you add to bin/webpack get sent to webpack. For example, you can pass
--debug
to switch loaders to debug mode. See webpack CLI debug options for more information on the available options. - You can also pass additional options to the command to run the webpack-dev-server and start the webpack-dev-server with the option
--debug-webpacker
If you get the error ENOENT: no such file or directory - node-sass
on deploy with
assets:precompile
or bundle exec rails webpacker:compile
you may need to
move Sass to production dependencies
.
Move any packages that related to Sass (e.g. node-sass
or sass-loader
) from
devDependencies
to dependencies
in package.json
. This is because
webpacker is running on a production system with the Rails workflow to build
the assets. Particularly on hosting providers that try to detect and do the right
thing, like Heroku.
However, if you get this on local development, or not during a deploy then you
may need to rebuild node-sass
. It's a bit of a weird error; basically, it
can't find the node-sass
binary. An easy solution is to create a postinstall
hook to ensure node-sass
is rebuilt whenever new modules are installed.
In package.json
:
"scripts": {
"postinstall": "npm rebuild node-sass"
}
- If you get this error
Can't find hello_react.js in manifest.json
when loading a view in the browser it's because webpack is still compiling packs. Webpacker uses amanifest.json
file to keep track of packs in all environments, however since this file is generated after packs are compiled by webpack. So, if you load a view in browser whilst webpack is compiling you will get this error. Therefore, make sure webpack (i.e./bin/webpack-dev-server
) is running and has completed the compilation successfully before loading a view.
- If you get this error while trying to use Elm, try rebuilding Elm. You can do
so with a postinstall hook in your
package.json
:
"scripts": {
"postinstall": "npm rebuild elm"
}
-
This could happen if
webpacker:install
step is skipped. Please runbundle exec rails webpacker:install
to fix the issue. -
If you encounter the above error on heroku after upgrading from Rails 4.x to 5.1.x, then the problem might be related to missing
yarn
binstub. Please run following commands to update/add binstubs:
bundle config --delete bin
./bin/rails app:update:bin # or rails app:update:bin
If you are running webpack on Windows, your command shell may not be able to interpret the preferred interpreter
for the scripts generated in bin/webpack
and bin/webpack-dev-server
. Instead you'll want to run the scripts
manually with Ruby:
C:\path>ruby bin\webpack
C:\path>ruby bin\webpack-dev-server
Invalid configuration object. webpack has been initialised using a configuration object that does not match the API schema.
If you receive this error when running $ ./bin/webpack-dev-server
ensure your configuration is correct; most likely the path to your "packs" folder is incorrect if you modified from the original "source_path" defined in config/webpacker.yml
.
If your tests are timing out or erroring on CI it is likely that you are experiencing the slow Elm compilation issue described here: elm-compiler issue #1473
The issue is related to CPU count exposed by the underlying service. The basic solution involves using libsysconfcpus to change the reported CPU count.
Basic fix involves:
# install sysconfcpus on CI
git clone https://github.com/obmarg/libsysconfcpus.git $HOME/dependencies/libsysconfcpus
cd libsysconfcpus
.configure --prefix=$HOME/dependencies/sysconfcpus
make && make install
# use sysconfcpus with elm-make
mv $HOME/your_rails_app/node_modules/.bin/elm-make $HOME/your_rails_app/node_modules/.bin/elm-make-old
printf "#\041/bin/bash\n\necho \"Running elm-make with sysconfcpus -n 2\"\n\n$HOME/dependencies/sysconfcpus/bin/sysconfcpus -n 2 $HOME/your_rails_app/node_modules/.bin/elm-make-old \"\$@\"" > $HOME/your_rails_app/node_modules/.bin/elm-make
chmod +x $HOME/your_rails_app/node_modules/.bin/elm-make
This error occurs because you are trying to minify by terser a pack that's already been minified by Webpacker. To avoid this conflict and prevent appearing of ExecJS::RuntimeError error, you will need to disable uglifier from Rails config:
// production.rb
# From
Rails.application.config.assets.js_compressor = :uglifier
# To
Rails.application.config.assets.js_compressor = Uglifier.new(harmony: true)
Angular: WARNING in ./node_modules/@angular/core/esm5/core.js, Critical dependency: the request of a dependency is an expression
To silent these warnings, please update config/webpack/environment.js
// environment.js
const webpack = require('webpack')
const { resolve } = require('path')
const { environment, config } = require('@rails/webpacker')
environment.plugins.append('ContextReplacement',
new webpack.ContextReplacementPlugin(
/angular(\\|\/)core(\\|\/)(@angular|esm5)/,
resolve(config.source_path)
)
)
If compiling is not producing output files and there are no error messages to help troubleshoot. Setting the webpack_compile_output configuration variable to 'true' in webpacker.yml may add some helpful error information to your log file (Rails log/development.log or log/production.log)
# webpacker.yml
default: &default
source_path: app/javascript
source_entry_path: packs
public_root_path: public
public_output_path: complaints_packs
webpack_compile_output: true