I created a simple gem by doing:
testgem.gemspec
Gem::Specification.new do |s|
s.name = 'testgem'
s.version = '0.0.1'
s.summary = "code generation"
s.authors = ['asdf']
end
created the following file layout:
testgem.gemspec
Gemfile
lib/
lib/testgem.rb
lib/testgem/other.rb
ran the following:
gem build testgem.gemspec
WARNING: no description specified
WARNING: no email specified
WARNING: no homepage specified
Successfully built RubyGem
Name: testgem
Version: 0.0.1
File: testgem-0.0.1.gem
installed it:
gem install ./testgem-0.0.1.gem
Successfully installed testgem-0.0.1
1 gem installed
tested to see if irb can see it:
irb
require 'testgem'
oadError: cannot load such file -- testgem
I'm using Ruby 1.9.3-p194
It seems to be installed if I do:
gem list
..
testgem (0.0.1)
..
What could be the issue?
You need to add your lib to the search path. Just add
$:.push File.expand_path("../lib", __FILE__)
on top of your .gemspec
When you use require in Ruby, you are trying to load a file, not a gem. The file could of course be contained in a gem, and by convention a gem will have a file with the same name as the gem itself so that if you wanted to use the gem foo you would use require 'foo'. This isn’t always the case though, for example to use the bcrypt-ruby gem you need to require 'bcrypt'.
Additionally a gem doesn’t necessarily have to contain any filles at all. An example of this is the rails gem, which doesn’t contain any files itself (at least in version 3.2), but has dependencies to the various Rails components, so that you can install them all in one step.
In your case, although you have a lib/testgem.rb file in your gems project directory, you are not including it in your gem. You need to specify which files should be included, the default is to not include anything.
To simply include all the files in your project directory, you can add something like:
s.files = Dir.glob '**/*'
to your gemspec.
You need to require 'rubygems' first.
Related
I can't require third party code in my .gemspec file. I would like to require a semver library to manage my version number. Why can't I require gems inside my .gemspec?
I have a workaround for my particular problem. What I am interested in the specific reason I can't require code from inside a gemspec. I feel like I am missing something about how Rubygems work. Thanks!
lib = File.expand_path('../lib', __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require 'semver'
Gem::Specification.new do |spec|
spec.add_dependency "semver2", "~> 3.4.2"
spec.version = SemVer.find.to_s[1..-1]
end
Running bundle install results in the following error:
$ bundle
[!] There was an error parsing `Gemfile`: There was a LoadError while loading example.gemspec:
cannot load such file -- semver from
/opt/pose/auto/stack-overflow/example/example.gemspec:3:in `<main>'
Obviously there is some point before which you cannot depend on 3rd party gems to be on your LOAD_PATH. I am asking for an explanation of where that point is. My guess is because my Gemfile references my gemspec and Bundler had not loaded all the dependencies yet, but that is a guess.
A .gemspec is just a Ruby script like any other Ruby script. Basically the only thing that is "special" is that it is run in an environment where certain libraries have already been required, such as rubygems/specification.
requireing libraries works just like in any other Ruby script.
I'm in the process of writing my first ruby gem and I'm a little new at the whole structure of setting up gems. My understanding from reading this guide is that in order to create an executable for my gem I need to do the following:
Add a line to my gemspec specifiying the name of the executable like this:
s.executables << 'gemname'
Build the gem with
gem build gemname.gemspec
Install the gem locally (if you try to install by pushing to rubygems each time you'll end up having to change versions constantly) with
gem install gemname-0.0.1.pre.gem
Then test it out with
gemname foo-arguments, --bar-options
If I go through all these steps then on #4 I get the following error:
$ gemname
zsh: command not found: gemname
Assuming that the executable a file starting with a shebang and located at gemname/bin/gemname
Everything works just fine if I navigate to the root of the gem folder and run bin/gemname to test out the executable.
Here is a gist of my current gemspec and the gem source is available on github here.
You need to add all the files that need be included with the gem in spec.files. You missed to add the files that you have in the bin directory.
For example, I have the following configuration from one of my gems:
Gem::Specification.new do |spec|
spec.files = Dir["{bin,lib}/**/*", "LICENSE", "README.md"]
spec.test_files = Dir["spec/**/*"]
spec.require_paths = ["lib"]
spec.executables = ["yarr"]
end
Your gemspec is trying to change the load path. I would suggest fixing that first, because what you're reporting seems to be consistent with a gem not being able to find its files.
Look at your gemspec for this code:
lib = File.expand_path('../lib', __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
Then see http://guides.rubygems.org/patterns/
"Gems should not change the $LOAD_PATH variable. RubyGems manages this for you. Code like this should not be necessary ..."
See http://guides.rubygems.org/patterns/ for various solutions to load using the existing load path, and helpers such as require_relative.
In addition you need to ensure your executable is, well, executable.
$ chmod a+x bin/gemname
Otherwise the command won't be available after building the gem.
I use:
rvm 1.25.19 (stable)
ruby 1.9.3p545
I install gem rake command
gem install rake
I understand that $LOAD_PATH should contain the paths:
~/.rvm/rubies/ruby1.9/gems/rake/lib
~/.rvm/rubies/ruby1.9/gems/rake/bin
I execute command:
ruby -e 'puts $LOAD_PATH'
output:
/home/slip/.rvm/rubies/ruby-1.9.3-p545/lib/ruby/site_ruby/1.9.1
/home/slip/.rvm/rubies/ruby-1.9.3-p545/lib/ruby/site_ruby/1.9.1/x86_64-linux
/home/slip/.rvm/rubies/ruby-1.9.3-p545/lib/ruby/site_ruby
/home/slip/.rvm/rubies/ruby-1.9.3-p545/lib/ruby/vendor_ruby/1.9.1
/home/slip/.rvm/rubies/ruby-1.9.3-p545/lib/ruby/vendor_ruby/1.9.1/x86_64-linux
/home/slip/.rvm/rubies/ruby-1.9.3-p545/lib/ruby/vendor_ruby
/home/slip/.rvm/rubies/ruby-1.9.3-p545/lib/ruby/1.9.1
/home/slip/.rvm/rubies/ruby-1.9.3-p545/lib/ruby/1.9.1/x86_64-linux
why path to gem 'rake' don't add?
Installing a gem in Ruby doesn’t automatically add that gem’s files to the load path. When you require a file, first the existing load path is searched and if no matching file is found then Rubygems searches the installed gems for the file. If such a gem is found, then it is activated, which is when the gem’s lib directory is added to the load path.
Here’s an example using the Haml gem:
puts "Before:"
puts $LOAD_PATH
puts
require 'haml'
puts "After:"
puts $LOAD_PATH
This produces:
Before:
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/site_ruby/1.9.1
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/site_ruby/1.9.1/x86_64-darwin10.8.0
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/site_ruby
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/vendor_ruby/1.9.1
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/vendor_ruby/1.9.1/x86_64-darwin10.8.0
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/vendor_ruby
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/x86_64-darwin10.8.0
After:
/Users/matt/.rvm/gems/ruby-1.9.3-p448/gems/tilt-1.4.1/lib
/Users/matt/.rvm/gems/ruby-1.9.3-p448/gems/haml-4.0.5/lib
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/site_ruby/1.9.1
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/site_ruby/1.9.1/x86_64-darwin10.8.0
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/site_ruby
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/vendor_ruby/1.9.1
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/vendor_ruby/1.9.1/x86_64-darwin10.8.0
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/vendor_ruby
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1
/Users/matt/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/x86_64-darwin10.8.0
See how the lib directories for Tilt (which is a dependency of Haml) and Haml have been added to the start of the load path.
In the case of some gems, such as Rake, this is complicated by the fact they are part of the standard library and so are already on the load path. If you changed the example above to use require 'rake' then you wouldn’t see any change in the load path. In this situation you can specify you want to use the gem version with the gem method. This activates the gem in question, placing its lib directory at the start of the load path so when you later call require you will load the correct version.
For example, this script
require 'rake'
puts Rake::VERSION
produces 0.9.2.2 with Ruby 1.9.3, as that is the version of Rake included in the standard library. However this script:
gem 'rake'
require 'rake'
puts Rake::VERSION
produces 10.1.1, since that is the current highest version of the Rake gem installed on my system. You can also specify a particular gem version by providing a second argument to gem (this is the same syntax as used in Gemfiles). Note that the gem method doesn’t require any files, you have to do that as a separate step.
How do gems like "rails", "rspec", and "cucumber" allow user to use commands that start with their gem name??
rails new project
rspec spec
cucumber features
Not all gems have this ability. For example, when I type json even though I have it installed, I get
-bash: json: command not found
Gem's .gemspec file looks like this:
Gem::Specification.new do |s|
s.name = "haml"
s.version = "3.1.8"
....
s.executables = ["haml", "html2haml"]
end
This means that when installing this Gem (haml-3.1.8 in this case) also links to executables (also called "binstubs") will be created for the files haml and html2haml which are found inside the gem's bin/ directory.
In this case, for example the file bin/haml could look like:
#!/usr/bin/env ruby
require 'rubygems'
require 'haml'
puts Haml::VERSION
From rubygems.org documentation on building Gems:
In addition to providing libraries of Ruby code, gems can also expose
one or many executable files to your shell’s PATH. Probably the best
known example of this is rake. Another very useful one is
prettify_json.rb, included with the JSON gem, which formats JSON in a
readable manner (and is included with Ruby 1.9).
[...]
Adding an executable to a gem is a simple process. You just need to
place the file in your gem’s bin directory, and then add it to the
list of executables in the gemspec. Let’s add one for the Hola gem.
[...]
The executable file itself just needs a shebang in order to figure out
what program to run it with.
[...]
All it’s doing is loading up the gem, and passing the first command
line argument as the language to say hello with.
These gems have binaries that can be executed from the CLI. Most gems do not need this functionality and only provide code extensions.
Edit: They may not be 'binaries'. They can be just executable Ruby code as well. Thanks #holger
The title is the question, and here's the context that prompts it.
The Gemfile:
source "http://rubygems.org"
# Specify your gem's dependencies in the gemspec
gemspec
Here is the top of the rackup file:
require 'rubygems'
require "bundler/setup"
On running the rackup file an error is thrown:
<module:Rack>': GemName is not a class (TypeError)
Why? Because I'm writing a piece of Rack middleware, and the standard layout is:
lib/
rack/
gem_name.rb
gem_name/
version.rb
gem_name.rb will contain:
module Rack
class GemName
version.rb will contain:
module Rack
module GemName
VERSION = "0.0.1"
Finally, the gem_name.gemspec will contain:
require "rack/flash-in-the-pan/version"
#...
s.version = Rack::GemName::VERSION
Naming a module and a class by the same name isn't a problem as long as you don't require both files at the same time. Normally, this wouldn't happen, as you either need the version for building the gem, or you need to run the gem library, only one or other gets required.
But, this time I decided to use Bundler to manage the gem's dependencies. When requiring the gem library via bundler it obviously runs the gemspec too. I can "fix" it easily enough, I define the version number by hand in the gemspec.
So back to my question - why does Bundler need to look in the gemspec at the library's runtime?
bundler (1.0.21)
Any insight is much appreciated.
Whenever you run bundler, it has to parse the Gemfile to actually figure out what gems need to be loaded, what has to be added to $LOAD_PATH and so on. As part of that, it has to parse gemspec.
The Gemfile.lock contains info on all of the gems as well as the dependencies to save startup time, but it doesn't alleviate the need for it to parse the Gemfile.
There are various ways you could work around it. Two simple ones would be to use File.read and some regex to pull out the version. Or require the gem_name.rb and gem_name/version.rb files.