Our projects with parallel_tests and cucumber used to have a patched failure logger as the one from parallel_tests was missing spaces which resulted in the output not being a valid rerun argument. With version 4.9.1 output of ParallelTests::Cucumber::FailuresLogger was fixed.

You can remove the patch (e.g. features/support/cucumber_failures_logger.rb) and switch the logger in config/cucumber.yml back to ParallelTests::Cucumber::FailuresLogger.

Thanks to Dominik for [the fix](https://github.com/grosser/parallel_tests/commit/...

It can be hard to understand what causes a browser scroll smoothly or instantly. CSS, JavaScript and the browser settings all have options to influence the scroll behavior. They all interact with each other and sometimes use the same words for different behavior.

CSS

Scrolling elements can use the scroll-behavior CSS property to express a preference between smooth and instant scrolling.

Preferring instant scrolling

CSS can prefer instant scrolling behavior:

html {
  scroll-behavior: auto; /* the default */
}

An `aut...

This note is a reminder that there is something called AppArmor that could cause weird errors ("File not found", "Can't open file or directory", ...) after configuration changes, e.g. when changing MySQL's data directory.

Remember to have a look at AppArmor's daemon configuration (usually at /etc/apparmor.d/) if you change daemon configuration and run into errors such as the one above.

Rails middlewares are small code pieces that wrap requests to the application. The first middleware gets passed the request, invokes the next, and so on. Finally, the application is invoked, builds a response and passes it back to the last middleware. Each middleware now returns the response until the request is answered. Think of it like Russian Dolls, where each middleware is a doll and the application is the innermost item.

You can run rake middleware to get the ordered list of used middlewares in a Rails application:

$> rake midd...

PostgreSQL offers three character types for your columns:

• character varying(n) (also called varchar or just string): Contents are limited to n characters, smaller contents are allowed.
• character(n): All contents are padded with spaces to allocate exactly n characters.
• text: There is no upper or lower character limit (except for the absolute maximum of 1 GB).

The documentation states:

There is no performance difference among these three types, apart ...

Say you wrap your index view in a form to apply different filters like pagination or a search query. On submit, your index view changes when the filters are applied (through up-submit and up-target).
Now you want to enable more data-specific filters using a separate "Filters" button that opens a popup to not overload your UI.

Filter bar:

Filter popup:

The problem is th...

With the new unpoly client side templates (available since 3.10) there's another way to substitute the ids of inserted nested attribute forms which I added to this card.

Ruby 3.0 introduced a breaking change in how it treats keyword arguments.

There is an excellent blog post on the official Ruby blog going into the details. You should probably read that, but here is a slightly abbreviated version:

What changed

When the last argument of a method call is a Hash, Ruby < 3 automatically converted it to to Keyword Arguments. If you call a method in Ruby >= 3 that accepts keyword arguments, eithe...

When accepting GIF images, you will also accept animated GIFs. Resizing them can be a time-consuming task and will block a Rails worker until the image is processed.

Save yourself that trouble, and simply tell ImageMagick to drop any frames but the first one.

Add the following to your uploader class:

process :remove_animation

private

def remove_animation
  if content_type == 'image/gif'
    manipulate! { |image| image.collapse! }
  end
end

You may also define that process for specific versions only (e.g. only for thum...

JavaScript has no built-in functions to compare two objects or arrays for equality of their contained values.

If your project uses Lodash or Underscore.js, you can use _.isEqual():

_.isEqual([1, 2], [2, 3]) // => false
_.isEqual([1, 2], [1, 2]) // => true

If your project already uses Unpoly you may also use up.util.isEqual() in the same way:

up.util.isEqual([1, 2], [2, 3]) // => false
up.util.isEqual([1, 2], [1, 2]) // => true

If you are wri...

To apply transparency to an element, you can use opacity in CSS. However, sometimes you don't want to make the entire element transparent, only a color.
Using not-so-modern CSS, you can simply generate non-opaque versions of a color. This card describes how to do that.

Note that we're not talking about defining colors with transparency. This is about the case where you have a color but need a more transparent variant of it (e.g. for a border, background, etc.), and where your component does that without defining the transparent variant ...

The currentColor CSS keyword references the current text color and can be used to apply an element's text color to other properties.
Using modern CSS, you can also use it to calculate colors from it. This card describes how to invert currentColor, but you can use this technique for other calculations as well.

How to invert currentColor

They key is CSS' hsl() function and from keyword for it:

--inverted-color: hsl(from ...

The :nth-child pseudo class is commonly used for targeting elements based on their position within a parent container, for example the third element in a list or every even-numbered item. However, :nth-child can do more.

In modern CSS specifications (Level 4), there’s an additional feature that lets you use :nth-child in combination with a list of css selectors. This way, you can ta...

You can do so much more than console.log(...)! See the attached link for a great breakdown of what the developer console can give you.

Some of my favorites:

console.log takes many arguments

E.g. console.log("Current string:", string, "Current number:", 12)

Your output can have hyperlinks to Javascript objects

E.g. console.log("Check out the current %o, it's great", location)

[Di...

When you build a JSON API you need to come up with a style to represent attributes, pagination, errors or including associated objects. Instead of reinventing the wheel, you may reuse successful API designs.

JSON API

JSON:API specifies common features found in most JSON APIs, like pagination, ordering and nested resources. The spec looks very similar to how one would build an API with Rails and uses similar patterns. Even if you don't plan on supporting the whole spec, it can still make sense to know how th...

When your Rails application server raises error, Capybara will fail your test when it clears the session after the last step. The effect is a test that passes all steps, but fails anyway.

Capybara's behavior will help you to detect and fix errors in your application code. However, sometimes your application will explode with an error outside your control. Two examples:

• A JavaScript library references a source map in its build, but forgets to package the source map
• CarrierWave cleans up an upload or cache file after the record was delet...

When you want to filter records in a model where a string column roughly matches a given term, you can use PostgreSQL’s trigram similarity search.

Writing a fuzzy query in Rails

User.where("similarity(name, ?) > 0.3", "John")

This finds all users where the name is similar to "John" with a similarity score above 0.3.

You can tune the threshold:

• Closer to 1.0 = stricter match
• Closer to 0.0 = looser match

Ordering by best match

User
  .where("similarity(name, ?) > 0.3", "John")
  .order(Arel.sql("similarity(n...

Purpose:
Interactively rebase your current branch onto main, keeping the original base commit (i.e. not rebasing onto main directly).

Use Case:
Useful when you've branched off a long-lived feature branch and want to clean up your commits without changing the original base. Afterwards you will be able to rebase one clean commit interactively onto main without going through each commit individually using git rebase -i main.

What it does:

• Opens an interactive rebase UI to choose squash/edit/fixup for each co...

When you send automated emails from a noreply@-address, and the recipient has an out of office enabled, the autoreply bounces and they get an additional email with an error message.

To prevent the recipient's auto-response and the following error message you can set the email header Auto-Submitted: auto-generated in your mailer, for example like this:

class NoReplyMailer < ApplicationMailer
  default from: 'noreply@yourapp.com', 'Auto-Submitted' => 'auto-generated'
end  

You can check the maximum client Redis database size in Sidekiq with this command.

Sidekiq.redis { |redis| puts redis.info.fetch('maxmemory_human') }
#=> 512.00M

If you just want the maximum database size for a known Redis database URL you can use the Redis Ruby client or the Redis CLI:

Redis database size via Ruby client

irb(main):002> Redis.new(url: 'redis://localhost:16380/1').info.fetch('maxmemory_human')
=> "512.00M"

Redis database size via CLI

$ redis-c...

If you want to fill in textareas with multiple lines of text (containing line breaks / new lines) you can use Cucumber's docstrings:

And I fill in "Comment" with:
  """
  This is a long comment.
  With multiple lines.

  And paragraphs.
  """

The step definition is part of the spreewald gem

You can use local copies of gems in your Gemfile like this:

gem 'spreewald', path: '~/gems/spreewald'

As soon as you have bundled your project with the local copy of the gem, all code changes in the copy will be available on your project. So you can for example set a debugger or add console output in the gem and use it from your project.
If you checked out the gem with your versioning tool, you can easily reset your changes afterwards or make a pull request for the gem if you improved it.

Don't commit a Gemfile with local path...

To safely transport an arbitrary string within a URL, you need to percent-encode characters that have a particular meaning in URLs, like & or =.

If you are using Rails URL helpers like movies_path(:query => ARBITRARY_STRING_HERE), Rails will take care of the encoding for you. If you are building URLs manually, you need to follow this guide.

Ruby

In Ruby, use CGI.escape:

# ✅ good
CGI.escape('foo=foo&bar=bar')
=> "foo%3Dfoo%26bar%3Dbar"

Do not ever use `URI.en...

Added reference to git who.