In general, you should not put a block element inside an inline element. So don't do this:

<span>
  <div>text</div>
</span>

The browser will think you wrote invalid HTML by accident, and will sometimes reorder elements silently.

There is one notable exception: It's OK to wrap block elements in a <a> tag in HTML5 (not 4). The spec says:

The a element may be wrapped around entire paragraphs, lists, tables, and so forth, even entire sections, so long ...

If you get an error like this for a puppet mount:

$ > puppet agent --test 
Info: Retrieving pluginfacts
Info: Retrieving plugin
Info: Loading facts
Info: Caching catalog for example.makandra.de
Info: Applying configuration version '1483001792'
Info: Computing checksum on file /etc/fstab
Info: FileBucket got a duplicate file {md5}34b9adc036cf1dbd2392df84f921547d
Notice: /Stage[main]/Foobar/Swap_file::Files[default]/Mount[/var/swapfile]/ensure: defined 'ensure' as 'defined'
Error: /Stage[main]/Foobar/Swap_file::Files[default]/Mount[/var/s...

So you're getting this failure when running bundle install on an older project:

Your Gemfile.lock is corrupt. The following gems are missing from the DEPENDENCIES section: 'archive-tar-minitar' 'hoe' 'rcov'

This happens when you are using a new version of Bundler with a project that was bundled with a very old version of Bundler. For reasons unknown, the Bundler dependency API returns different dependencies for some gems (like ruby-debug or rainpress) than the dependencies found in the downloaded gemspecs. While old versi...

This card tries to summarize by example the different uses of heredoc.

• In Ruby << vs. <<- vs. <<~
• In Rails strip_heredoc vs. squish

strip_heredoc should be used for a text, where you want to preserve newlines. (multi-line -> multi-line)

squish should be used for a text, where you want to squish newlines. (multi-line -> one-line)

Ruby 2.3+

def foo
  bar = <<~TEXT
    line1
    line2
    line3
  TEXT
  puts bar.inspect
end
foo => "line1\nline2\nline3\n"

Read more: [Unindent HEREDOCs in Ruby 2.3](/m...

The linked article states that CSS breakpoints should group "similar" screen sizes and thus be at:

• 600px "narrow"
• 900px "medium"
• 1200px "wide"
• (1800px) "huge"

By choosing these breakpoints, most device screens will be somewhere between two breakpoints, and not at the very edge of them.

The ranges could be called:

• narrow (< narrow)
• medium (narrow - medium)
• normal (medium - wide)
• wide (wide - huge)
• huge (> huge)

If your external displays not switching on or showing a weird behavior (for e.g. all displays getting the same configuration all the time) you can fix it by switching off all external displays and re-enabling only one in the first step. Afterwards you can apply your whole configuration via xrandr. This behavior could be a bug in the kernel and may be fixed in linux 4.8.

Example display configuration

Screen 0: minimum 8 x 8, current 5760 x 1200, maximum 32767 x 32767
eDP1 connected 1920x1080+0+0 (normal left inverted right x axis...

When running tests via parallel_tests, you may encounter an error:

cannot load such file -- parallel_tests/gherkin/runtime_logger
Error creating formatter: ParallelTests::Gherkin::RuntimeLogger (LoadError)

This will happen when you upgrade Bundler to version 1.13.x and appears to be "by design" since there is a Bundler config option to restore previous behavior.

You can fix it by setting that flag. You should commit the resulting config file into the repository!

bundle config --local disable_exec_load true

There is a Git...

When testing your command line application with Aruba, you might need to stub out other binaries you don't want to be invoked by your test.

Aruba Doubles is a library that was built for this purpose. It is not actively maintained, but works with the little fix below.

Installation

Install the gem as instructed by its README, then put this Before block somewhere into features/support:

Before do
  Arub...

When you're writing specs for ActiveRecord models that use memoization, a simple #reload will not do:

it 'updates on changes' do
  subject.seat_counts = [5]
  subject.seat_total.should == 5
  # seat_total is either memoized itself, or using some
  # private memoized method
  
  subject.seat_counts = [5, 1]
  subject.seat_total.reload.should == 6 # => Still 5
end

You might be tempted to manually unmemoize any memoized internal method to get #seat_total to update, but that has two disadvant...

We used zeroclipboard.js in some of our projects but now we switched to clipboard.js because it does not rely on flash. Flash support of the major browsers has ended.

Some more advantages of clipboard.js:

• it consists only of a single javascript file, so it does not trigger additional requests with rails
• it automagically provides user feedback by selecting the text it has copied
• it provides callbacks for success and error which make it easier to add custom behaviour after copying to the clipboar...

Yesterday I stumbled across a talk in which the guy mentioned module sub-classing. I was curious what you can do with it and found his blog post with a cool example. It allows you to inject some state into the module you are including elsewhere. Check it out!

class AttributeAccessor < Module
  def initialize(name)
    @name = name
  end

  def included(model)
    super
    define_accessors
  end

  private

  def define_accessors
    ivar = "@#{@name}"
    define_writer(ivar)
    define_reader(ivar)
  end

  def define_writer(ivar)
    ...

In order to have monitoring for Sidekiq (like queue sizes, last run of Sidekiq) your application should have a monitoring route which returns a json looking like this:

{
  "sidekiq": {
    "totals": {
      "failed": 343938,
      "processed": 117649167
    },
    "recent_history": {
      "failed": {
        "2016-11-06": 1,
        "2016-11-07": 46,
        "2016-11-08": 0,
        "2016-11-09": 0,
        "2016-11-10": 0
      },
      "processed": {
        "2016-11-06": 230653,
        "2016-11-07": 230701,
        "2016-11-08"...

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...

When working with custom transactions and use ActiveRecord::Rollback you may encounter unexpected behaviour if you try to roll back your changes.

tl;dr

When using nested transactions, ActiveRecord::Rollback might not do what you expect, since it will only roll back the inner, but not the outer transaction.

You can fix this behavior by using transaction(joinable: false) but this leads to a bunch of different problems.

When you don't need an explicit ActiveRecord::Rollback, don't worry about any of this and just use a plan `tran...

VCR lets you configure how it matches requests to recorded cassettes:

In order to properly replay previously recorded requests, VCR must match new
HTTP requests to a previously recorded one. By default, it matches on HTTP
method and URI, since that is usually deterministic and fully identifies the
resource and action for typical RESTful APIs.

You can customize how VCR matches requests using the `:match_requests_on casse...

If you want to find the commits that touched a specific text in a file, use

git log -S 'text in the code' -- path/to/file

If you use tig you may run a similar command to get a navigatable list of affected files:

tig -S'text in the code'

Example

Here is an example, where the move of the convert_number_column_value(value) method in active record is traced (simplified output):

git log -n 1 --pretty=oneline -S 'convert_number_column_value(value)' -- activerecord/lib/active_record/base.rb
ceb33f84933639d3b6...

We often use VCR to stub external APIs. Unfortunately VCR can have problems matching requests to recorded cassettes, and these issues are often hard to debug.

VCR's error messages mostly look like this and are not very helpful:

An HTTP request has been made that VCR does not know how to handle:
         POST http://another-site.de:9605/json/index

VCR fails if the request does not exactly look like the request it has recorded. If the request is d...

SVG is an acronym for "scalable vector graphics". SVGs should be used whenever an image can be described with vector instructions like "draw a line there" or "fill that space" (they're not suited for photographs and the like). Benefits are the MUCH smaller file size and the crisp and sharp rendering at any scale.

It's a simple, old concept brought to the web – half-heartedly. While actually all browsers pretend to support SVG, some barely complex use cases get you beyond common browser support.

In the bas...

You might get the above error message when cloning certain git repositories (for example the rails repository). It indicates that there is a malformed timestamp in some commit, and your git installation is configured to validate it.

As a workaround, you can disable the validation using

git config --global fetch.fsckobjects false

This settings seems to be the default for most git installations anyways.

We have released a new library Gemika to help test a gem against multiple versions of Ruby, gem dependencies and database types.

Here's what Gemika can give your test's development setup (all features are opt-in):

• Test one codebase against multiple sets of gem dependency sets (e.g. Rails 4.2, Rails 5.0).
• Test one codebase against multiple Ruby versions (e.g. Ruby 2.1.8, Ruby 2.3.1).
• Test one codebase against multiple database types (currently MySQL or PostgreSQL).
• Compute a matrix of all possib...

Say you have an RGBA color that you need as a non-transparent color because of reasons.

Basically, this is possible. Just understand that you will convert your RGBA color for exactly one base background color as you are giving up transparency.
Most likely, your background is white, so you'll use #fff as that for examples below.

Simple approach

When your know the RGBA color's base RGB color (e.g. your brand color that you RGBA'd for some hover effect), you can simply use the mix function instead of rgba.

Before:

backgroun...

Same requests are recorded only once in vcr. Replaying a test fails, if you trigger the same request multiple times. The error message is somehow confusing, as your cassette contains the request:

An HTTP request has been made that VCR does not know how to handle

If you want to allow to match a request multiple times, you need to configure this explicit with allow_playback_repeats: true. Some exa...

Similar to our snippet that runs all Cucumber features matching a given string, the following will run all modified or new Cucumber features by looking at your git status:

git status --short | grep -v '^ D ' | grep '.feature' | sed 's/.. //' | tr '\n' ' ' | xargs geordi cucumber

If you want to know what each of the above commands does, see [explainshell](http://explainshell.com/explain?cmd=git+status+--short+%7C+grep+-v+%27%5E+D+%27+%7C+grep+%27.feature%27+%7C+sed+%27s%2F..+%2F%2F%27+%7C+tr+%27%5Cn%27+%27+%27+%7C...