Use rbenv-each to run a command for every installed Ruby version
The linked rbenv plugin rbenv-each is very helpful to keep QoL gems up to date that are not part of the Gemfile.
For example, you can bump the geordi
version for all your rubies with the following command:
rbenv each gem update geordi
Another useful example would be to bulk-update bundler
or rubygems.
Note that rbenv-each
hasn't been updated since 2018, but it is fully functiona...
Don't use log level :debug in your production environments
Catch phrase
You don't want sensitive user data in your logs.
Background
Rails per default filters sensitive data like passwords and tokens and writes [FILTERED]
to the logs. The code which is responsible for enabling that usually lives in filter_parameter_logging.rb
(Rails.application.config.filter_parameters
). Here is an example of a filtered log entry:
Unfiltered:
`User Load (0.4ms) SELECT "users".* FROM "users" WHERE "users"."token" = $1 LIMIT $2 [["token", "secret-token"], ["LIMIT", 1]]`
After the filter is appl...
Upgrade Rails: Awareness list
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
Upgrade to Rails 7
- Don't use log level :debug in your production environments
- [Rails 7.1: Take care of...
Advanced plotting in Ruby with Gnuplot
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...
Split your parallel tests by execution time and keep execution logs up to date
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 The required logs for this might be outdated since you manually have to update and push them into your repository.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...
Lightning Talk: Coverage based Test Case Prioritization in Ruby on Rails
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.
...
Git restore vs. reset for reverting previous revisions
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...
redirect_to and redirect
There are multiple ways to redirect URLs to a different URL in Rails, and they differ in small but important nuances.
Imagine you want to redirect the following url https://www.example.com/old_location?foo=bar
to https://www.example.com/new_location?foo=bar
.
Variant A
You can use ActionController::Redirecting#redirect_to
in a controller action
class SomeController < ActionController::Base
def old_location
redirect_to(new_location_url(params.permit(:foo)))
end
end
This will:
- It will redirect with a 302 st...
Do not pass params directly into url_for or URL helpers
Rails' url_for
is useful for generating routes from a Hash, but can lead to an open redirect vulnerability.
Your application's generated route methods with a _url
suffix are also affected because [they use url_for
unter the hood](https://github.com/rails/rails...
Do not use "permit!" for params
Rails' Strong Parameters enable you to allow only specific values from request params
to e.g. avoid mass assignment.
Usually, you say something like params.permit(:email, :password)
and any extra parameters would be ignored, e.g. when calling to_h
.
This is excellent and you should definitely use it.
What is permit!
and why is it dangerous?
However, there is also params.permit!
whic...
Chromedriver issue #4550 breaks the user agent for device emulation via device name
Newest versions of Chromedriver breaks the user agent for device emulation via device name. In previous versions the user agent of the emulated device was set. In the newest versions the user agent differs from the emulated device.
- Version Chrome: 116.0.5845.110
- Version Chromedriver: 116.0.5845.96
- Bug: https://bugs.chromium.org/p/chromedriver/issues/detail?id=4550&q=userAgent&can=2
- Setting: https://chromedriver.chromium.org/capabilities
In Capybara an affected config looks like following:
Capybara.register_driver :mobi...
Minifying object properties in JavaScript files
An introduction to mangling
When you minify ("compress", "optimize") your JavaScript for production, the names of your functions and variables will be renamed for brevity. This process is often called mangling.
E.g. if this is your source code:
function function1() {
function2()
}
After mangling it would look like this:
function a() {
b()
}
Object properties are not mangled by default
Minfiers never mangle properties by default, as this can be an unsafe transformation. This leads to larger file sizes if...
Postgres in Alpine docker container: sorting order might differ
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...
Node: How to run a globally installed package with npx
You can tell npm
to install a package globally with npm -g install @puppeteer/browsers
. However, it seems that its not possible that npx
can run commands from global packages without referencing the global package path.
Example
Installing @puppeteer/browsers
globally:
$ npm -g install @puppeteer/browsers
The globally installed package @puppeteer/browsers
can not be access via npx
:
$ npx --no-install @puppeteer/browsers
npm ERR! canceled # Error message when package is not installed
But it is installed g...
RSpec: How to write isolated specs with cookies
Background
Rails offers several methods to manage three types of different cookies along with a session storage for cookies. These are normal, signed and encrypted cookies.
By following the happy path of testing a web application, that is only the main use-case is tested as a integration test and the rest as isolated (more unit ...
How to transition the height of elements with unknown/auto height
If you want to collapse/expand elements with dynamic content (and thus unknown height), you can not transition between height: 0
and height: auto
.
Doing it properly, with modern CSS features
In the past, you might have resorted to bulky JavaScript solutions or CSS hacks like transitioning between max-height: 0
and max-height: 9999px
. All of them were awkward and/or have several edge cases.
With modern CSS, there is actually a way to do it properly:
Just use a display: grid
container which transitions its grid row height betwe...
Use -webkit-line-clamp to natively truncate long (multi-line) texts with an ellipsis
Note: You won't need this for single lines of text. In this case it is better to just use the text-overflow
property: Use CSS "text-overflow" to truncate long texts
You can use -webkit-line-clamp
in your CSS/SASS to natively render an ellipsis (...
) after a specific amount of lines for a multi-line text in your HTML.
Earlier, it was necessary to implement JavaScript solutions like Superclamp.js to enable this because the browser support has been rather limited...
Using git patchfiles to speed up similar implementation tasks
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...
CarrierWave: Processing images with libvips
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....
How to find child nodes that match a selector with JavaScript
Using querySelector
or querySelectorAll
in JavaScript, you can easily find descendants of a node that match a given selector.
But what if you want to find only children (i.e. direct descendants) of an element?
Easy: use :scope
. It references the element on which DOM API methods are being called:
element.querySelectorAll(':scope > .your-selector')
Example
Consider this HTML
<body>
<div id="container1">
<div id="container1a">foo</div>
<div id="container1b">bar</div>
<div id="container1c">baz</...
Balance your texts today with text-wrap: balance
So you have a heading that is just barely wider than the container it should fit into, and it wraps a single word to a new line and it's not really pretty?
Cry no more, for you can use text-wrap: balance
today to fix that. At least in some browsers.
When browsers encounter a text-wrapping element with text-wrap: balance
style, they will try breaking to a new line sooner, if it balances out the width of lines.
text-wrap: unset |
text-wrap: balance |
---|---|

- avoids "magic numbers" (don't say e.g. ...
Best practice: How to manage versions in a package.json
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...
Best practice: How to manage versions in a Gemfile
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...