How to: Solve gem loaded specs mutex
Use bundler > 1.15
to fix Gem::LOADED_SPECS_MUTEX (NameError)
.
Given the following project:
ruby -v
ruby 1.8.7
bundler -v
Bundler version 1.13.7
gem -v
1.8.30
rails -v
Rails 3.2.22.1
Running specs or features resulted in:
uninitialized constant Gem::LOADED_SPECS_MUTEX (NameError)
The previous settings described in Maximum version of Rubygems and Bundler for Ruby 1.8.7 and Rails 2.3 (even the rails version was rails 3.2 and not 2.3) seems not to work here, so I used (also described in the ca...
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...
Katapult 0.3.0 released
Katapult 0.3.0 brings Rails 5 and Ruby 2.5 support with a new design, plus a ton of smaller features, fixes and improvements.
Features
- Generating a Rails 5.1.4 app on Ruby 2.5.0
- Dropped asset pipeline in favor of Webpacker
- The generated application now has a sleek, simple design based on Bootstrap
- Employing Unpoly
- New application model DSL shortcut
crud
for "create a model and a web UI with crud actions" - The generated application model is now a transformable e...
Error during Rails 5 upgrade: Environment data not found in the schema
This error is raised because your old database does not have a configured environment yet, which Rails 5 enforces.
If this error occurs while migrating your parallel test databases, make sure to update the parallel_tests
gem first: current versions fix this. If you're still using Cucumber < v3, the latest version of parallel_tests
will be 2.18.0.
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 ...
xlsxtream: Streaming & Fast XLSX Spreadsheet Writer for Ruby
When writing XLSX files, there are gems like rubyXL or axlsx. While they do offer features like formatting or graphs, to represent spreadsheet cells, they have to keep several Ruby objects in memory. When writing huge files, both will become slow and consume lots of memory.
Enter Xlsxtream, a Ruby XLSX library with less features (e.g. no individual cell styles) but which does away with the memory issue by streaming ...
chromedriver-helper gem in Gemfile might break you selenium tests (of other projects)
Summary: Don't add chromedriver-helper to the Gemfile
- the executables might break your tests in projects where
chromedriver-helper
is not in the Gemfile - developers with different chrome versions will have problems using the same
chromedriver-helper
version
Background
If you install the chromedriver-helper
gem, but don't have it in you Gemfile, your selenium tests might fail with:
Selenium::WebDriver::Error::WebDriverError: unable to connect to chromedriver 127.0.0.1:9515
The reason is that chromedriver-helper
ov...
Fix for: "can't convert nil to String" when running "gem update --system"
When attempting to update RubyGems, depending on updates your previously performed, you might run into an error
ERROR: While executing gem ... (TypeError)
can't convert nil into String
Fix this by running
gem uninstall rubygems-update -a -x
Fixing flaky E2E tests
An end-to-end test (E2E test) is a script that remote-controls a web browser with tools like Selenium WebDriver. This card shows basic techniques for fixing a flaky E2E test suite that sometimes passes and sometimes fails.
Although many examples in this card use Ruby, 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
And I click on B
And I click on C
Then I should see effects of C
A test like this works fine...
Bundler 2 will rename Gemfile and Gemfile.lock
TL;DR: Bundler 2.0 will rename Gemfile
to gems.rb
and Gemfile.lock
to gems.locked
(sic).
The old filenames will be supported until the release of Bundler 3.0.
Import Excel files without running into memory limitations
There are several gems that make it easy to read and process xlsx files. Parsing the entire file at once however is error-prone since each cell is transformed to a ruby object - sometimes including thousands of formatted but empty cells.
As of today, I found two promising alternatives that provide a stream-based access to spradsheet rows:
- Roo supports multiple spreadsheet types like ODS or CSV and has a quite large contributor base
- [Creek](https://github.com/pythonicrubyis...
How to use a local gem in your Gemfile
You can use local copies of gems in your Gemfile
like this:
gem 'spreewald', :path => '~/gems/spreewald'
As soon as you have bundled your project with the local copy of the gem, all code changes in the copy will be available on your project. So you can for example set a debugger or add console output in the gem and use it from your project.
If you checked out the gem with your versioning tool, you can easily reset your changes afterwards or make a pull request for the gem if you improved it.
Don't commit a Gemfile with local pat...
Speed up better_errors
If you use the Better Errors gem, you will sometimes notice that it can be very slow. This is because it sometimes renders a huge amount of data that will actually be hard to render for your browser.
You can significantly improve performance by adding this to config/initializers/better_errors
:
if defined?(BetterErrors) && Rails.env.development?
module BetterErrorsHugeInspectWarning
def inspect_value(obj)
inspected = obj.inspect
if inspected.size > 20_000
inspec...
Rails: How to write custom email interceptors
Nowadays it is fairly easy to intercept and modify mails globally before they are sent. All you have to do is register an interceptor class which responds to .delivering_email(message)
. This card will show you two common use cases.
Subject prefix:
Usually you want to prefix the subject line of emails with the current environment (except production) so you can differentiate between production mails and mails from other environments. Of course a...
Working with or without time zones in Rails applications
Rails supports time zones, but there are several pitfalls. Most importantly because Time.now
and Time.current
are completely different things and code from gems might use one or the other.
Especially configuring an application that cares only about one time zone is a bit tricky.
The following was tested on Rails 5.1 but should apply to Rails 4.2 as well.
Using only local time
Your life will be easier if your application does not need to support time zones. Disable them like this:
config.time_zone = 'Berlin' # Your local ...
Listing all gems on a private gem server
You can use gem list
to list all gems available from a remote gem server:
gem list -r --clear-sources -s 'https://user:password@gemserver.tld/'
This is useful to debug cases where Bundler complains of a gem existing in more than one gem source.
Standard Gems
Ruby's standard library is in the process of being gemified. It will soon - Ruby 2.5 - consist of RubyGems, which can be updated independently from Ruby.
This might mean smoother Ruby upgrades in the future. If breaking API changes happen in standard gems, we can update these before upgrading Ruby.
Middleman configuration for Rails Developers
Middleman is a static page generator that brings many of the goodies that Rails developers are used to.
Out of the box, Middleman brings Haml, Sass, helpers etc. However, it can be configured to do even better. This card is a list of improvement hints for a Rails developer.
Gemfile
Remove tzinfo-data
and wdm
unless you're on Windows. Add these gems:
gem 'middleman-livereload'
gem 'middleman-sprockets' # Asset pipeline!
gem 'bootstrap-sass' # If you want to use Bootstrap
gem 'byebug'
gem 'capistrano'
gem 'capistrano-mid...
Howto: Require a gem that is not in Gemfile
In case you want to require a gem, that is not in the Gemfile of you bundle and therefore not in your loadpath, you need to add the path manually and require the gem afterwards.
Expected error
Requiring a gem, that is not in the Gemfile
or .gemspec
, will cause an LoadError
exception:
require 'example_gem' => LoadError: cannot load such file -- example_gem
Adding a gem to the loadpath temporary
- You need to install the
gem
gem install 'example_gem'
- Then you need to require the path where the gem was install...
How to use Parallel to speed up building the same html partial multiple times (for different data)
The parallel-gem is quite easy to use and can speed up rendering time if you want to render the same partial multiple times (e.g. for rendering long lists of things).
If your parallelized code talks to the database, you should ensure not to leak database connections.
Consider you want to render a list of groups with their members as json. You can use a partial for the rendering of group members, b...
Sending errors to sentry from development
For the initial setup or changes in the sentry reporting it might be useful to enabled reporting of sentry in development. Don't commit these changes and prefer to report to the staging environment. As other developers might be confused of these errors try to given them a proper message and delete them afterwards.
- Add
config.raven_dsn = 'your-dns'
inconfig/environments/development.rb
. - Add development to existing environments in the
Raven.configure
block:config.environments = ['development', 'staging', 'production']
. - ...
Beware: Nested Spreewald patiently blocks are not patient
Note: The behaviour of Spreewald's within
step is as described below for version < 1.9.0; For Spreewald >= 1.9.0 it is as described in Solution 1.
When doing integration testing with cucumber and selenium you will often encounter problems with timing - For example if your test runs faster than your application, html elements may not yet be visible when the test looks for them. That's why Spreewald (a collection of cucumber steps) has a concept of doing things patiently
, which means a given b...
Generating barcodes with the Barby gem
Barby is a great Ruby gem to generate barcodes of all different sorts.
It includes support for QR codes via rQRCode; if you need to render only QR codes, you may want to use that directly.
Example usage
Generating a barcode is simple:
>> Barby::Code128.new('Hello Universe').to_png
=> "\x89PNG\r\n\u001A..."
Configuration
Barby supports several barcode types and you must require all necessary files explicitly.
For the example a...
Getting error Bundler::Plugin::API::Source
Error:
/home/.../ruby/gems/2.1.0/gems/bundler-1.14.3/lib/bundler/rubygems_ext.rb:45:in `full_gem_path': uninitialized constant Bundler::Plugin::API::Source (NameError)
Solution: Upgrade Rubygems beyond 2.6.9.