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Writing a README for a project

Rails applications and ruby gems should have a README that gives the reader a quick overview of the project. Its size will vary as projects differ in complexity, but there should always be some introductory prose for a developer to read when starting on it.

Purpose

That's already the main purpose of a project README: Give a new developer a quick overview of the project. In sketching this outline, the README should notify the reader of any peculiarity he needs to know of.

Remember that in a few months, you'll be a kind of "new …

Linked contentAuto-destruct in 31 days

Updated: New Gem safe_cookies: Have your cookies as secure and HttpOnly as possible

Card is now deprecated and on auto-destruct.

The gem is no longer maintained, because flagging Secure is irrelevant when using HSTS.

Also, IE11 received HSTS support in 2015 so there is really no reason any more.

Note that security audits may still request Secure cookies. Don't try to discuss the sense of this requirement with them, just [make them happy](https://makandracards.com/makandra/53693-rails-flagging-all…

Sass partial names must always start with an underscore

Be careful to name any file @imported by SASS with a leading underscore.

SASS files not beginning with an underscore will be rendered on their own, which will fail if they are using variables or mixins defined elsewhere. (For me it broke only in production, which may be due to some settings in SASS-GEM/lib/sass/plugin/rails.rb.)

From the SASS docs:

The underscore lets Sass know that the file is only a partial file and that it should not be generated into a CSS file.

Rails: Rest API post-mortem analysis

This is a personal post-mortem analysis of a project that was mainly build to provide a REST API to mobile clients.

For the API backend we used the following components:

  • Active Model Serializer (AMS) to serializer our Active Record models to JSON.
  • JSON Schema to test the responses of our server.
  • SwaggerUI to document the API.

It worked

The concept worked really good. Here are two points that were extraordinary compared to normal Rails project with many UI components:

  • Having a Rails application, that has no UI components (only…

How to: Validate dynamic attributes / JSON in ActiveRecord

PostgreSQL and ActiveRecord have a good support for storing dynamic attributes (hashes) in columns of type JSONB. But sometimes you are missing some kind of validation or lookup possibility (with plain attributes you can use Active Record's built-in validations and have your schema.rb).

One approach about being more strict with dynamic attributes is to use JSON Schema validations. Here is an example, where a project has the dynamic attributes analytic_stats, that we can use to store analytics from an external measurement tool.

  • A g…
Linked content

Structuring Rails applications: the Modular Monorepo Monolith

Root Insurance runs their application as a monolithic Rails application – but they've modularized it inside its repository. Here is their approach in summary:

Strategy

  • Keep all code in a single repository (monorepo)
  • Have a Rails Engine for each logical component instead of writing a single big Rails Application
  • Build database-independent components as gems
  • Thus: gems/ and engines/ directories instead of app/
  • Define a dependency graph of components. It should have few edges.
  • Gems and Engines can be extracted easier once nece…

Capybara 'fill_in': Ambiguous match for different input names

When you have two inputs, where one contains the name of the other (eg. Name and Name with special treatment), Capybara's fill_in method will fail with the following message:

Ambiguous match, found 2 elements matching visible field "Name" that is not disabled (Capybara::Ambiguous)

You can force Capybara to match exactly what you are typing (which makes your tests better anyways) with match: :prefer_exact:

name = 'Name'
value = 'Bettertest Cucumberbatch'
fill_in(field, with: value, match: :prefer_exact)

Furthermore…

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Showing a custom maintenance page while deploying

Add a custom maintenance page for each vhost (require capistrano 3.x):

Installation

Add this line to your application's Gemfile:

gem 'capistrano', '~> 3.0'
gem 'capistrano-maintenance', '~> 1.0'

Add this line to you application's Capfile:

require 'capistrano/maintenance'

Enable task

Present a maintenance page to visitors. Disables your application's web interface by writing a #{maintenance_basename}.html file to each web server. The servers must be configured to detect the presence of this file, and if it i…

Repeats

Running "bundle update" without arguments might break your application

Calling bundle update (without arguments) updates all your gems at once. Given that many gems don't care about stable APIs, this might break your application in a million ways.

To stay sane, update your gems using the applicable way below:

Projects in active development

Update the entire bundle regularily (e.g. once a week). This ensures that your libraries are up-to-date while it's easy to spot major version bumps which may break the app.

Projects that have not been updated in a while

  1. [Update a single gem conservatively](htt…
Linked content

A Migration Path to Bundler 2+

Bundler 2 introduced various incompatibilites und confusing behavior. To add to the confusion, Bundler's behavior changed after the release of their version 2.

The linked article explains what happened.

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Automated "git bisect" will make your day

So you're hunting down a regression (or just a bug) and want to use git bisect to find out when it was introduced? Smart kid.
If you have a shell command ready to reveal if your current state is good or bad, you can have git do most of the work for you.

Using git bisect run <your command> you can tell git that your command will reveal the issue; git on the other hand will use the return value of that call to decide if the state is good or bad. …

Repeats

How to update the bundler version in a Gemfile.lock

  1. Install the latest bundler version:

    gem install bundler
    Fetching bundler-2.1.2.gem
    Successfully installed bundler-2.1.2
    1 gem installed
    
  2. Update the bundler version in you Gemfile.lock:

    bundle _2.1.2_ update --bundler  
    

Note: Older Ruby and Rails can not use the latest bundler 2 version, so you need to stay on bundler 1.

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Sidekiq: Problems and Troubleshooting

When using Sidekiq in your application, you must write thread-safe code.

This wiki page also lists gems that are known to be unsafe on threaded applications.
When adding a gem that will also be used by a Sidekiq worker, make sure to confirm it's thread-safe.

Repeats

I18n fallback locales

When you need to create a locale for a language variant (like Austrian for German), you probably don't want to duplicate your entire de.yml file only to change a few minor exceptions for our Austrian friends.

Luckily, the I18n gem used by Rails has a fallback feature where you can make one locale file fall back to another if no translation is available.

In the example above you would have a config/locales/de_DE.yml:

de_DE:
    # hundreds of translations here

… and another …

Repeats

Fixing flaky integration tests

This card shows basic techniques for fixing a flaky integration test suite that sometimes passes and sometimes fails. "Integration test" is a test script that remote-controls a web browser with tools like Selenium WebDriver.

Although the examples in this card use Cucumber and Selenium, the techniques are applicable to all languages and testing tools.

Why tests are flaky

Your tests probably look like this:

When I click on A
When I click on B
When I click on C
Then I should see effects of C

A test like this works fine most of t…

Repeats

Configuring RubyGems to not install documentation by default

When installing gems, a lot of time is spent building locally installed documentation that you probably never use.

We recommend you disable documentation generation for gem install by default.
Note that Bundler won't install documentation, so this advice applies only when installing gems manually.

If you don't already have it, create a ~/.gemrc file. The gemrc is a Yaml file, so add the following line to add default switches to the gem command.

gem: --no-document

(If you do n…

Bundler: Releasing a gem with enabled 2FA

Rubygems supports a 2FA for your account. Once enabled you need to provide your personal OTP code for every release. Despite the CLI of the rake release task does not work well with the command promt for your OTP code with Bundler versions < 2.0.2. It just looks like the task is frozen:

Image

  • Workaround 1: Just type your OTP code and hit enter, your gem is released afterwards.
  • Workaround 2: Upgrade to Bundler >= 2.0.2.. Your supported Ruby versions for this gem must be all >= 2.3.

Wh…

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ActiveSupport includes Timecop-like helpers

ActiveSupport (since 4.1) includes test helpers to manipulate time, just like the Timecop gem:

  • To travel a relative amount of time, use travel:

    travel 1.day
    
  • To travel to a specific moment in time, use travel_to:

    travel_to 1.hour.from_now
    
  • To freeze a specific time, use freeze_time (ActiveSupport 5.2+):

    freeze_time 1.hour.from_now
    

All those methods may also receive a block to call and restore time afterwards. If you don't provide a block, you must call `travel_bac…

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