Imagine you have 2 HTML boxes. The first one has a margin-bottom of let's say 30px and the second one a margin-top of 20px. After rules of collapsing margins have been applied we have a margin of 30px (not 50px) between these two boxes . This is because no addition of both margins takes place but the maximum of both is applied. This behavior is called collapsing margins.
Oftentimes it is a good behavior but collapsing margins can be annoying, too. For example child el...
When your public-facing application has a longer downtime for server maintenance or long migrations, it's nice to setup a maintenance page to inform your users.
When delivering the maintenance page, be very careful to send the correct HTTP status code. Sending the wrong status code might get you kicked out of Google, or undo years of SEO work.
Here are some ways to shoot yourself in the foot during maintenance:
Ag (aka "the silver searcher") is a very fast replacement for grep.
It will parse your .gitignore for additional speedup. To ignore even more files (node_modules, *.min.js etc), add an .ignore with syntax identical to .gitignore.
See Faster Grepping in Vim for hints about vim integration.
By default, Devise sends all emails synchronously with deliver_now.
To change that, Devise's readme suggests overwriting the send_devise_notification method like this:
class User
def send_devise_notification(notification, *args)
devise_mailer.send(notification, self, *args).deliver_later
end
end
However, there is one problem: When deliver_later enqueues the mail with ActiveJob, the job arguments are logged. In case of a password reset, this includes the password reset token, which should not be logged.
A...
The way that Javascript schedules timeouts and promise callbacks is more complicated than you think. This can be the reason why callbacks are not executed in the order that they are queued.
Please read this article!
This is an extract of the example in the article which demonstrates the execution order of tasks and microtasks.
console.log('script start');
setTimeout(function() {
console.log('setTimeout');
}, 0);
Promise.resolve().then(function() {
console.log('promise1');
}).then(function() {
console.log('promise2');
})...
To restart all tasks monitored by God, don't use god restart. This command is only meant to soft-restart a given process or group.
Instead you should:
god stop
god terminate
god start -c yourgodconfig.god
Instantiating ActiveRecord objects comes expensive. To speed up things, you can choose a more direct way to talk to your database: the ActiveRecord::ConnectionAdapters::DatabaseStatements module.
Using the module and its methods is not suggested in the usual in-app workflow, as validations, callbacks, custom getters/setters etc. are ignored. However, for database-centered stuff like migrations, these fill the gap between writing pure SQL and full...
Chromedriver (or selenium-webdriver?) will not reliably scroll elements into view before clicking them, and actually not click the element because of that.
We've seen this happen for elements which are just barely in the viewport (e.g. the upper 2px of a 40px button). Our assumption is that the element is considered visible (i.e. Capybara::Selenium::ChromeNode#visible? returns true for such elements) but the Selenium driver wants to actually click the center of the element which is outside of the viewport.
We don't know who exactly i...
Browsers can auto fill-in one time codes if advised. Use it like this:
<input autocomplete="one-time-code">
Demo: https://twitter.com/sulco/status/1320700982943223808
Browser support is pretty good since mid-2022 (Chrome 93+, no Firefox).
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!
You don't want sensitive user data in your logs.
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...
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.
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.
...
It is a common misunderstanding that all [op]=-operators work the same way, but actually they don't.
||= and &&=
Those are special cases, because the assignment will only happen if the first variable passes the check (false or nil for || and true for &&).
a ||= b # => a || (a = b)
a &&= b # => a && (a = b)
But still, if reading a has any side effects, they will take place regardless of to what a resolves.
[op]=
Assignment will always take place, no matter the value of a.
Geordi's cucumber command has a --rerun option that reruns failing tests the given number of times. Usage:
geordi cucumber path/to/features --rerun=2
geordi cucumber path/to/features -r2
Cucumber will save a file tmp/parallel_cucumber_failures.log containing the filenames and line number of the failed scenarios after a full test run. Normally you can say cucumber -p rerun (rerun is a profile defined by default in config/cucumber.yml) to rerun all failed scenarios.
Here are a few al...
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...
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.
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:
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...
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.
permit! and why is it dangerous?However, there is also params.permit! whic...
There are various ways to run external commands from within Ruby, but the most powerful ones are Open3.capture3 and Open3.popen3. Since those can do almost everything you would possibly need in a clean way, I prefer to simply always use them.
Behind the scenes, Open3 actually just uses Ruby's spawn command, but gives you a much better API.
Basic usage is
require 'open3'
stdout_str, error_str, status = Open3.capture3('/some/binary', 'with', 'some', 'args')
if status.success?...
In a nutshell: Use git rebase --onto target-branch source-commit
target-branch means "branch you want to be based on"source-commit means "commit before your first feature commit"Let's say my-feature-branch is based on master and we want it to be based on production. Consider this history:
%%{init: { 'gitGraph': {'showCommitLabel': true, 'mainBranchName': 'production'}} }%%
gitGraph
commit id: "1"
commit id: "2"
branch master
commit id: "3"
commit id: "4"
branch my-feature...
It might sound trivial, but there is no such thing as a "hover" or "mouseover" state on touch devices. If your application is supposed to work on iPads, smartphones, etc., don't hide information behind a tooltip, and don't make controls appear when hovering over another element.
Generally, things that happen/appear when you hover an element should do the same when you click the element.
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.
In Capybara an affected config looks like following:
Capybara.register_driver :mobi...