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Ag: Very fast grep replacement

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.

Linked contentRepeats

Verifying doubles in RSpec 3

RSpec 3 has verifying doubles. This breed of mock objects check that any methods being stubbed are present on an instance of a given class. They also check methods aren't called with the wrong number of arguments.

This dual approach allows you to move very quickly and test components in isolation, while
giving you confidence that your doubles are not a complete fiction.

You should always prefer using a verifying double to using an old-...

Linked contentAuto-destruct in 14 days

ActiveType 1.4.0 released

Extended records now use their own I18n namespace when looking up translations for models or attributes. If the extended record's namespace does not contain a translation, the lookup will fall back to the base record's namespace.

For instance, given the following class hierarchy:

class User < ActiveRecord::Base

class User::Form < ActiveType::Record[User]

The call ExtendedParent.human_attribute_name(:foo) would first look up the key in activerecord.attributes.user/form first, then falls back to `activerecord.attributes...

Linked content

Introducing GoodJob 1.0, a new Postgres-based, multithreaded, ActiveJob backend for Ruby on Rails

GoodJob is a new background worker gem. It's compatible with ActiveJob.

We're huge fans of Sidekiq for its stability and features. One advantage of GoodJob over Sidekiq is that GoodJob doesn't require Redis. So in cases where you don't have Redis or don't want to pay for a Redis HA quorum node, this might be an alternative worth checking out.

Linked content

Fixing wall of warnings: already initialized constant Etc::PC_SYMLINK_MAX

These warnings are printed when the etc Gem is installed, while etc is also included in Ruby. Fix with:

gem uninstall etc

How to create giant memory leaks in AngularJS (and other client-side JavaScript)

This guide shows how to create an AngularJS application that consumes more and more memory until, eventually, the browser process crashes on your users.

Although this guide has been written for Angular 1 originally, most of the advice is relevant for all client-side JavaScript code.

How to observe memory consumption

To inspect the amount of memory consumed by your Javascripts in Chrome:

  • Open an incognito window
  • Open the page you want to inspect
  • Press Shift + ESC to see a list of Chrome processes...

Concurrency issues with find-as-you-type boxes

Find-as-you-type boxes are usually built by observing changes in a text field, and querying the server via AJAX for search results or suggestions when the field has changed.

A common problem with this implementation is that there is no guarantee that AJAX responses are evaluated in the same order as the original requests. The effect for the user is that the search results are flashing back and forth while the user is typing the query, and when the user has stopped typing the last results don't always match the final query.

You won't notice...


MySQL: CONCAT with NULL fields


CONCAT('foo', 'bar', NULL) = NULL

the NULL always wins in MySQL.

If you would rather treat NULL as an empty string, use CONCAT_WS (concatenation with separator) instead:

CONCAT_WS('', 'foo', 'bar', NULL) = 'foobar'


In PostgreSQL the NULL is not viral in CONCAT:

CONCAT('foo', 'bar', NULL) = 'foobar'

Sentry: Different ways of deferring notifications for an issue

We use Sentry to be informed about different kinds of issues. One of the key features is that you are not getting spammed if many errors of the same kind occur in a small timespan.
If an issue pops up the usual workflow is to fix the code and mark the issue as "resolved" in Sentry. Only new or resolved issues trigger another email notification when they are proxied through Sentry.

This workflow does not fit well for issues we cannot fix, e.g. when consuming an external API that is sometimes down. In such cases you ...


HTML forms with multiple submit buttons

Most forms have a single submit button that will save the record when pressed.

Sometimes a form needs additional submit buttons like "accept" or "reject". Such buttons usually attempt a state transition while updating the record.

To process a form with multiple buttons, your server-side code will need to know which button was pressed. To do so you can give each submit button a different [formaction] attribute. This will override the ...

Git: Merge a single commit from another branch

This is called "cherry-picking".

git cherry-pick commit-sha1

Note that since branches are nothing but commit pointers, cherry-picking the latest commit of a branch is as simple as

git cherry-pick my-feature-branch

Be aware that cherry-picking will make a copy of the picked commit, with its own hash. If you merge the branch later, the commit will appear in a history a second time (probably without a diff since there was nothing left to do).

Also see our advice for [cherry picking to production branches](https://makandraca...


Automatically validating dependency licenses with LicenseFinder

Open-source software (OSS) is great. Anyone can use virtually any open-source code in their projects.

Well, it depends. Licenses can make things difficult, especially when you are developing closed-source software. Since some OSS licenses even require the employing application to be open-sourced as well (looking at you, GPL), you cannot use such software in a closed-source project.

To be sure on this, we have developed a project-level integration of Pivotal's excellent [license_finder](https://g...


ActiveRecord: String and text fields should always validate their length

If you have a :string or :text field, you should pair it with a model validation that restricts its length.

There are two motivations for this:

  • In modern Rails, database types :string and :text no longer have a relevant size limit. Without a validation a malicious user can quickly exhaust the hard drive of your database server.
  • In legacy Rails (or database schemas migrated from legacy Rails), database types :string and :text had a database-side length constraint. When the user enters a longer string, the ActiveRecord valida...

How to prevent Nokogiri from fixing invalid HTML

Nokogiri is great. It will even fix invalid HTML for you, like a browser would (e.g. move block elements out of parents which are specified to not allow them).

>> Nokogiri::HTML.fragment("<h1><p>foo</p><span>bar</span></h1>").to_s
=> "<h1></h1><p>foo</p><span>bar</span>"

While this is mostly useful, browsers are actually fine with a bit of badly formatted HTML. And you don't want to be the one to blame when the SEO guy complains about an empty <h1>.

To avoid said behavior, use Nokogiri::XML instead of Nokogiri::HTML when par...

Linked content

FactoryBot: Traits for enums

FactoryBot allows to create traits from Enums since version 6.0.0

The automatic definition of traits for Active Record enum attributes is enabled by default, for non-Active Record enums you can use the traits_for_enum method.


factory :user do
  traits_for_enum :role, %w[admin contact] # you can use User::ROLES here, of course

is equivalent to

factory :user do
  trait :admin do
    role { 'admin' }

  trait :contact do
    role { 'c...

The HTML5 video element

# Basic HTML example
<video poster="preview_image.png" controls>
  <source src="or_here.webm" type="video/webm" />
  <source src="alternative_if_browser_cant_pay_first_source.mp4" type="video/mp4" />
  <track src="optional_subtitles.vtt" kind="subtitles" srclang="de" label="Deutsch" default>

# Javascript API (notable methods and properties)
video = document.querySelector('video')
video.load() // Reset to the beginning and select the best available source
video.currentSrc // The selected source

Shorthand function properties in ES6

Here is an ES5 object literal with two string properties and a function property:

let user = { 
  firstName: 'Max',
  lastName: 'Muster',
  fullName: function() { return this.firstName + ' ' + this.lastName }

user.fullName() // => 'Max Muster'

In ES6 we can define a function property using the following shorthand syntax:

let user = { 
  firstName: 'Max',
  lastName: 'Muster',
  fullName() { return this.firstName + ' ' + this.lastName }

user.fullName() // => 'Max Muster'

We can also define a gette...

The JavaScript Object Model: A deep dive into prototypes and properties

Speaker today is Henning Koch, Head of Development at makandra.

This talk will be in German with English slides.


As web developers we work with JavaScript every day, even when our backend code uses another language. While we've become quite adept with JavaScript at a basic level, I think many of us lack a deep understanding of the JavaScript object model and its capabilities.

Some of the questions we will answer in this talk:

  • How does the new keyword construct an object?
  • What is the differen...
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