A Rails script lives in lib/scripts and is run with bin/rails runner lib/scripts/.... They are a simple tool to perform some one-time actions on your Rails application. A Rails script has a few advantages over pasting some prepared code into a Rails console:

• Version control
• Part of the repository, so you can build on previous scripts for a similar task
• You can have tests (see below)

Although not part of the application, your script is code and should adhere to the common quality standards (e.g. no spaghetti code). However, a scri...

You can ignore certain commits when using git blame with the --ignore-revs-file option. This is handy to ignore large rubocop commits or big renamings in your project. You can add and commit a .git-blame-ignore-revs file in your project to track a list of commits that should be ignored.

# a list of commit shas
123...
456...

Use git blame with the --ignore-revs-file option and ignore the SHAs specified in .git-blame-ignore-revs.

git blame --ignore-revs-file .git-blame-ignore-revs

If you want to use this flag by def...

The linked article suggests an interesting way to speed up tests of Rails + Postgres apps:

PostgreSQL allows the creation of “unlogged” tables, which do not record data in the PostgreSQL Write-Ahead Log. This can make the tables faster, but significantly increases the risk of data loss if the database crashes. As a result, this should not be used in production environments. If you would like all created tables to be unlogged in the test environment you can add the following to your...

In the Gitlab settings the flag Auto-cancel redundant pipelines is enabled by default. This auto-cancels jobs that have the interruptible setting set to true (defaults to false e.g. to not cancel deploys by accident).

Consider to set the interruptible flag for test jobs to reduce the load on your runners like in the following example .gitlab-ci.yml:

rubocop:
  interruptible: true
  script:
    - 'bundle exec rubocop'

rspec:
  int...

When you find similar groups of expect calls in your tests, you can improve readability by extracting the group into its own matcher. RSpec makes this easy by allowing matchers to call other matchers.

Example

The following test checks that two variables foo and bar (1) have no lowercase characters and (2) end with an exclamation mark:

expect(foo).to_not match(/[a-z]/)
expect(foo).to end_with('!')

expect(bar).to_not match(/[a-z]/)
expect(bar).to end_with('!')

We can extract the repeated matcher chains into a custom m...

If you ever need to restore exact records from one database to another, Marshal might come in handy.

Marshal.dump is part of the ruby core and available in all ruby versions without the need to install anything. This serializes complete ruby objects including id, object_id and all internal state.

Marshal.load deserializes a string to an object. A deserialized object cannot be saved to database directly as the the dumped object was not marked dirty, thus rails does not see the need to save it, even if the object is not present in...

I recently stumbled over a problem that my feature tests broke in CI because of a mismatching chromedriver version.

In this specific project we have a fixed Chromium version in a Debian 12 environment instead of Chrome. The tests however used a recent chrome version instead.

$ chromedriver --version
ChromeDriver 117.0.5938.149 (e3344ddefa12e60436fa28c81cf207c1afb4d0a9-refs/branch-heads/5938@{#1539})
$ chromium --version
Chromium 117.0.5938.149 built on Debian 12.1, running on Debian 12.1

> WARN Selenium [:selenium_manager] The chromed...

Disclaimer

This card is a collection of guides and things to have in mind when upgrading to a specific version. It is not meant to be complete, so please feel free to contribute!

General workflows

• The official guide
• How to upgrade Rails: Workflow advice
• Upgrading Rails: Example commits

Upgrade to Rails 7

• Don't use log level :debug in your production environments
• [Rails 7.1: Take care of...

Besides Plotting graphs in Ruby with Gruff, which comes handy for many uses cases, you sometimes might need configuration for more advanced plots, e.g. for academic concerns. Then using Gnuplot, the first academic open source plotting software, might be a good option.

There are several wrappers for Ruby available and I mainly looked at one of the two most frequently used ones, which are [ruby_gnuplot](https://github.com/rdp/ruby_gnuplot...

Both knapsack and parallel_tests have the option to split groups by historic execution time. The required logs for this might be outdated since you manually have to update and push them into your repository.

The following card includes an option how you can keep them consistently up to date with no extra effort locally and/or remotely.

How to always split by execution logs

Parallel Tests

The parallel_tests gem has the option flag `--group...

For my computer science bachelor's thesis I programmed and evaluated a CLI Test Case Prioritization (TCP) tool for makandra. It has been written as a Ruby Gem and was tested and evaluated against one Ruby on Rails project. This card will summarize and present the research results, the evaluation and the programmed CLI tool.

The code has been published for educational purposes on GitHub. The german bachelor's thesis has also been included for download at the end.

...

The git doc states on the difference of these two commands:

• git-restore[1] is about restoring files in the working tree from either the index or another commit. This command does not update your branch. The command can also be used to restore files in the index from another commit.
• git-reset[1] is about updating your branch, moving the tip in order to add or remove commits from the branch. This operation changes the commit history.

git reset can also be used to restore th...

In CI test runs I noticed that string sorting order changed after switching from a debian-based PostgreSQL docker image to one that is based on Alpine Linux.

Debian image sorting: bar Bar foo Foo
Alpine image sorting: Bar Foo bar foo

Explanation

Alpine Linux is a very slim linux distribution that results in small docker image sizes (roughly 100MB instead of 150MB), so it's a popular choice. However, it does not have all comman locales installed and does not use all locales that a user installs by default.
Postgres orders string co...

Git log offers useful options for filtering. This card provides a short overview.

By message

Only commits that include a specific string in their commit message

git log --grep="tracker id"

By file

Only commits that introduced changes to a specific file

git log -- foo.rb bar.rb

Note

In case the file was renamed or moved the --follow option can be helpful

git log --follow -- foo.rb

By content

If you want to know when a specific line of code was added in the project

git log -S"def function_name"

By range

...

Sometimes you'll find yourself with a set of tasks that require similar code for different models. For example, if you start working at a new application that allows CRUDing pears and apples, each commit might look similar to this:

commit 41e3adef10950b324ae09e308f632bef0dee3f87 (HEAD -> ml/add-apples-12345)
Author: Michael Leimstaedtner <michael.leimstaedtner@acme.com>
Date:   Fri Aug 11 09:42:34 2023 +0200

    Add Apples as a new fruit

diff --git a/app/models/apple.rb b/app/models/apple.rb
new file mode 100644
index 0000000..a51...

Splitting up commits makes the process of reviewing often easier, since you can create several merge requests or review every commit one by one.

So when you find out that you have portions of the code that you initially didn't intend to change or when you do some refactoring along the current changes, you can use one of the following processes to split up the changes into several commits in a logical order:

#1 Splitting up the last n commits into m commits
#2 Adding changes to a previous commit
2.1 While adding new changes
2.2 S...

It most cases it's not necessary to add a version constraint next to your packages in the package.json. Since all versions are saved in a lockfile, everyone running yarn install will get exactly the same versions. Yarn saves this lockfile as yarn.lock and npm as package-lock.json.

There are some exceptions, where you can consider adding a version constraint to the package.json:

• You are not checking the lockfile into version control (not recommended)
• A specific package has a bug in a more recent version
• You want to ensure no...

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.

Git commands like diff use the less binary for their output representation.

I often find myself searching for strings like todo, then switching to the case-insensitive mode (-i) and re-doing my search.
Today I figured out that you can configure git to show case insensitive diffs every time:

git config --global core.pager 'less -i'

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...

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 ...