When you write your next CarrierWave uploader, consider processing your images with libvips instead of ImageMagick.

Reasons for libvips

There are several upsides to using libvips over ImageMagick:

• libvips is considerably faster and uses less memory.
• ImageMagick has a large attack surface that has repeatedly caused security incidents in the past (compare [ImageMagick CVEs](https://www....

When RubyMine reports Rubocop returning "exit code -1", upgrading Rubocop can be the fix:

gem install rubocop

"The logs" can be accessed with Ctrl + Shift + A > Show log in (Files). This opens your file manager at the IDEA log location; the log file is called "idea.log".
If your operating system supports it, right click into the file manager > Open in Terminal. There run tail -f idea.log to follow the log.

It most cases it's not necessary to add a version constraint next to your gems in the Gemfile. Since all versions are saved in the Gemfile.lock, everyone running bundle install will get exactly the same versions.

There are some exceptions, where you can consider adding a version constrain to the Gemfile:

• You are not checking in the Gemfile.lock into the version control (not recommended)
• A specific gem has a bug in a more recent version (adding a comment for the reason is highly recommended)
• You want to ensure no one upgrade...

If you have a fully functional CI pipeline but no CD, you might find yourself frequently waiting for CI (with "merge after pipeline succeeds") just to perform the deployment.

The following command waits for the next commit that lands on the current branch (should be main or similar) and proceeds to deploy staging afterwards:

alias await-deployment='watch -g git pull && bundle exec cap staging deploy'

Note

Use at your own risk.
You could be deploying code from someone else that was pushed to the same branch in the meantime.

Code splitting is a feature of esbuild that can keep huge libraries out of the main bundle.

How code splitting works

Like Webpack esbuild lets you use the await import() function to load code on demand:

// application.js
const { fun } = await import('library.js')

fun()

However, esbuild's code splitting is disabled by default. The code above would simply inline (copy) `l...

You can use rake --where task to find the source location that defines task:

bundle exec rake --where assets:precompile
rake assets:precompile              /home/henning/.rbenv/versions/2.6.6/lib/ruby/gems/2.6.0/gems/precompiled_assets-0.2.1/lib/precompiled_assets/tasks/assets.rake:5:in `block in <main>'

Debugging your integration tests, that run a headless Chrome inside a docker image, is tricky.

In many cases you can connect your Chrome to a remote docker container like docker-selenium, which should be the preferred way when you try to inspect a page within your integration test.

Otherwise you might be able to start your docker container with --net=host and access your local chromedriver in the host address space host.docker.internal.

If both options above don't work for you here is a...

Every Rails response has a default ETag header. In theory this would enable caching for multiple requests to the same resource. Unfortunately the default ETags produced by Rails are effectively random, meaning they can never match a future request.

Understanding ETags

When your Rails app responds with ETag headers, future requests to the same URL can be answered with an empty response if the underlying content ha...

tl;dr

asdf allows you to manage multiple runtime versions with a single CLI tool and is backwards compatible by supporting existing config files, like e.g. .nvmrc or .ruby-version.

Getting Started

1. Disable rbenv
   1.1 Delete or comment out source /home/$user/.rbenvrc in ~/.profile
   1.2 Delete or comment our eval "$(rbenv init -)" in ~/.bashrc or ~/.zshrc
   1.3 To take effect you may have to restart your shell or log out and log in again from your current linux session
2. Install asdf by following the official ...

By activating strict_loading you force developers to address n+1 queries by preloading all associations used in the index view. Using an association that is not preloaded will raise an ActiveRecord::StrictLoadingViolationError.

I think it's a good default to activate strict_loading in your controllers' #index actions. This way, when a change introduces an n+1 query, you...

Since Ruby 3.2.0 you can measure coverage support for eval statements and support has been added for the simplecov gem as well.

This allows to track coverage across ruby templates such as haml, erb, ...

Simply set this within simplecov

SimpleCov.start do
  enable_coverage_for_eval
end

SASS has an @extend keyword to inherit styles.

.alert
  color: red
  
  &.-framed
    border: 1px solid red
    padding: 5px
    
  &.-homepage
    @extend .-framed
    border-width: 5px

When compiling, SASS will simply join the selectors. Note how .-homepage is written where .-framed was defined:

...
.alert.-framed, .alert.-homepage {
  border: 1px solid red;
  padding: 5px;
}
.alert.-homepage {
  border-width: 5px;
}

Warning

Unfortunately, this does...

If you use a newer SSH key generated with the ED25519 algorithm instead of RSA (see Create a new SSH key pair), the deployment with Capistrano may fail with the following message:

The deploy has failed with an error: unsupported key type `ssh-ed25519'
net-ssh requires the following gems for ed25519 support:
 * ed25519 (>= 1.2, < 2.0)
 * bcrypt_pbkdf (>= 1.0, < 2.0)
See https://github.com/net-ssh/net-ssh/issues/565 for more information
Gem::LoadError : "ed25519 i...

In the past we validate and set default values for boolean attributes in Rails and not the database itself.

Reasons for this:

• Older Rails didn't support database defaults when creating new records
• Application logic is "hidden" in the database

An alternative approach, which currently reflects more the general opinion of the Rails upstream on constraints in the database, is adding default values in the schema of the database itself. We also ...

Sometimes I ran across a GitHub merge request of a gem where it was not completely obvious in which version the change was released. This might be the case for a bugfix PR that you want to add to your project.

Git can help you to find the next git tag that was set in the branch. This usually has the name of the version in it (as the rake release task automatically creates a git tag during release).

git name-rev --tags <commit ref>

Note

The more commonly used git describe command will return the last tag before a c...

After upgrading to Rails 6.1.7.2 one of our apps printed a wall of warnings while booting:

/var/www/app/shared/bundle/ruby/2.6.0/gems/net-protocol-0.2.1/lib/net/protocol.rb:68: warning: already initialized constant Net::ProtocRetryError
/home/deploy-app/.rbenv/versions/2.6.10/lib/ruby/2.6.0/net/protocol.rb:66: warning: previous definition of ProtocRetryError was here
/var/www/app/shared/bundle/ruby/2.6.0/gems/net-protocol-0.2.1/lib/net/protocol.rb:214: warning: already initialized constant Net::BufferedIO::BUFSIZE
/home/deploy-app/.rben...

Bundler so far ignored the version specified under BUNDLED_WITH in the Gemfile.lock. This had two annoying consequences:

• If the bundler version on your system was lower than in the Gemfile.lock, you got an error message and had to manually install the correct version.
• If the bundler version on your system was higher than in the Gemfile.lock, bundler silently updated the version in the Gemfile.lock to your system's bundler version. To avoid this, you had to always specify, which version you want to use for each bundler c...

Timecop is a great gem to set the current time in tests. However, it is easy to introduce flakyness to your test suite when you forget to reset the time after the test.
This might be the case if:

• a test freezes time and a later test does not work for frozen time
• a later test needs the real current date to work correctly

Often you only notice these kinds of errors in rare cases when tests are executed in a particular order.

A way to avoid this is by using block notation (`Timecop.travel(...) ...

In a Jasmine spec you want to spy on a function that is imported by the code under test. This card explores various methods to achieve this.

Example

We are going to use the same example to demonstrate the different approaches of mocking an imported function.

We have a module 'lib' that exports a function hello():

// lib.js

function hello() {
  console.log("hi world")
}

export hello

We have a second module 'client' that exports a function helloTwice(). All this does is call hello() ...

We usually rely on VCR and WebMock to prevent any real network connection when running our unit tests.

This is not entirely true: They are both limited to a set of HTTP libraries listed below (as of 2022). Direct calls to Kernel#open or OpenURI#open_uri are not mocked and will trigger real network requests even in tests. This might bite you e.g. in [older versions of CarrierWave](https://github.com/carrierwaveuploader/carrierwave/blob/0.11-stable/lib/carrierwave/upl...

The problem

If you're experiencing that your bundle install command fails with an error message like this, rubygems.org might have issues with their ipv6 connectivity:

$ bundle install
Fetching source index from https://rubygems.org/

Retrying fetcher due to error (2/4): Bundler::HTTPError Could not fetch specs from https://rubygems.org/ due to underlying error <timed out (https://rubygems.org/specs.4.8.gz)>

The (a little bit dirty) possible solution

If that's actually the case, then you can try to deprioritize the ipv...

Greg Molnar has written a neat article about creating a single-file Rails app.
This is not meant for production use but can be useful to try things out, e.g. when hunting down a bug or embedding a Rails app into the tests of a gem.

What you do is basically:

1. Put everything (gems, application config, database migrations, models, controllers) into a single .ru file, like app.ru.
2. Run it via rackup app.ru. (Hint: if your file is called config.ru, you can just run `rac...

Sometimes the need arises for SSL in local development. We have guides for different webservers, this one is for puma.

0. make sure mkcert is installed

1. create an SSL certificate for localhost with mkcert:

$ mkcert-v1.4.4-linux-amd64 localhost
Created a new local CA 💥
...

2. use the certificate in the Puma config config/puma.rb:

localhost_key = "#{File.join('localhos...