Gemfile(5) -- A format for describing gem dependencies for Ruby programs
========================================================================

## SYNOPSIS

A `Gemfile` describes the gem dependencies required to execute associated
Ruby code.

Place the `Gemfile` in the root of the directory containing the associated
code. For instance, in a Rails application, place the `Gemfile` in the same
directory as the `Rakefile`.

## SYNTAX

A `Gemfile` is evaluated as Ruby code, in a context which makes available
a number of methods used to describe the gem requirements.

## SOURCES (#source)

At the top of the `Gemfile`, add one line for each `Rubygems` source that
might contain the gems listed in the `Gemfile`.

    source "http://rubygems.org"
    source "http://gems.github.com"

Each of these _source_s `MUST` be a valid Rubygems repository.

## GEMS (#gem)

Specify gem requirements using the `gem` method, with the following arguments.
All parameters are `OPTIONAL` unless otherwise specified.

### NAME (required)

For each gem requirement, list a single _gem_ line.

    gem "nokogiri"

### VERSION

Each _gem_ `MAY` have one or more version specifiers.

    gem "nokogiri", ">= 1.4.2"
    gem "RedCloth", ">= 4.1.0", "< 4.2.0"

### REQUIRE AS (:require)

Each _gem_ `MAY` specify its main file, which should be used when autorequiring
(`Bundler.require`).

    gem "sqlite3-ruby", :require => "sqlite3"

This defaults to the name of the gem itself. For instance, these are identical:

    gem "nokogiri"
    gem "nokogiri", :require => "nokogiri"

### GROUPS (:group or :groups)

Each _gem_ `MAY` specify membership in one or more groups. Any _gem_ that does
not specify membership in any group is placed in the `default` group.

    gem "rspec", :group => :test
    gem "wirble", :groups => [:development, :test]

The Bundler runtime allows its two main methods, `Bundler.setup` and
`Bundler.require`, to limit their impact to particular groups.

    # setup adds gems to Ruby's load path
    Bundler.setup                    # defaults to all groups
    require "bundler/setup"          # same as Bundler.setup
    Bundler.setup(:default)          # only set up the _default_ group
    Bundler.setup(:test)             # only set up the _test_ group (but `not` _default_)
    Bundler.setup(:default, :test)   # set up the _default_ and _test_ groups, but no others

    # require requires all of the gems in the specified groups
    Bundler.require                  # defaults to just the _default_ group
    Bundler.require(:default)        # identical
    Bundler.require(:default, :test) # requires the _default_ and _test_ groups
    Bundler.require(:test)           # requires just the _test_ group

The Bundler CLI allows you to specify a list of groups whose gems `bundle install` should
not install with the `--without` option. To specify multiple groups to ignore, specify a
list of groups separated by spaces.

    bundle install --without test
    bundle install --without development test

After running `bundle install --without test`, bundler will remember that you excluded
the test group in the last installation. The next time you run `bundle install`,
without any `--without option`, bundler will recall it.

Also, calling `Bundler.setup` with no parameters, or calling `require "bundler/setup"`
will setup all groups except for the ones you excluded via `--without` (since they
are obviously not available).

Note that on `bundle install`, bundler downloads and evaluates all gems, in order to
create a single canonical list of all of the required gems and their dependencies.
This means that you cannot list different versions of the same gems in different
groups. For more details, see [Understanding Bundler](http://gembundler.com/rationale.html).

### PLATFORMS (:platforms)

If a gem should only be used in a particular platform or set of platforms, you can
specify them. Platforms are essentially identical to groups, except that you do not
need to use the `--without` install-time flag to exclude groups of gems for other
platforms.

There are a number of `Gemfile` platforms:

  * `ruby`:
    C Ruby (MRI) or Rubinius, but `NOT` Windows
  * `ruby_18`:
    _ruby_ `AND` version 1.8
  * `ruby_19`:
    _ruby_ `AND` version 1.9
  * `mri`:
    Same as _ruby_, but not Rubinius
  * `mri_18`:
    _mri_ `AND` version 1.8
  * `mri_19`:
    _mri_ `AND` version 1.9
  * `rbx`:
    Same as _ruby_, but only Rubinius (not MRI)
  * `jruby`:
    JRuby
  * `mswin`:
    Windows
  * `mingw`:
    Windows 'mingw32' platform (aka RubyInstaller)
  * `mingw_18`:
    _mingw_ `AND` version 1.8
  * `mingw_19`:
    _mingw_ `AND` version 1.9

As with groups, you can specify one or more platforms:

    gem "weakling",   :platforms => :jruby
    gem "ruby-debug", :platforms => :mri_18
    gem "nokogiri",   :platforms => [:mri_18, :jruby]

All operations involving groups (`bundle install`, `Bundler.setup`,
`Bundler.require`) behave exactly the same as if any groups not
matching the current platform were explicitly excluded.

### GIT (:git)

If necessary, you can specify that a gem is located at a particular
git repository. The repository can be public (`http://github.com/rails/rails.git`)
or private (`git@github.com:rails/rails.git`). If the repository is private,
the user that you use to run `bundle install` `MUST` have the appropriate
keys available in their `$HOME/.ssh`.

Git repositories are specified using the `:git` parameter. The `group`,
`platforms`, and `require` options are available and behave exactly the same
as they would for a normal gem.

    gem "rails", :git => "git://github.com/rails/rails.git"

A git repository `SHOULD` have at least one file, at the root of the
directory containing the gem, with the extension `.gemspec`. This file
`MUST` contain a valid gem specification, as expected by the `gem build`
command. It `MUST NOT` have any dependencies, other than on the files in
the git repository itself and any built-in functionality of Ruby or Rubygems.

If a git repository does not have a `.gemspec`, bundler will attempt to
create one, but it will not contain any dependencies, executables, or
C extension compilation instructions. As a result, it may fail to properly
integrate into your application.

If a git repository does have a `.gemspec` for the gem you attached it
to, a version specifier, if provided, means that the git repository is
only valid if the `.gemspec` specifies a version matching the version
specifier. If not, bundler will print a warning.

    gem "rails", "2.3.8", :git => "git://github.com/rails/rails.git"
    # bundle install will fail, because the .gemspec in the rails
    # repository's master branch specifies version 3.0.0

If a git repository does `not` have a `.gemspec` for the gem you attached
it to, a version specifier `MUST` be provided. Bundler will use this
version in the simple `.gemspec` it creates.

Git repositories support a number of additional options.

  * `branch`, `tag`, and `ref`:
    You `MUST` only specify at most one of these options. The default
    is `:branch => "master"`
  * `submodules`:
    Specify `:submodules => true` to cause bundler to expand any
    submodules included in the git repository

If a git repository contains multiple `.gemspecs`, each `.gemspec`
represents a gem located at the same place in the file system as
the `.gemspec`.

    |~rails                   [git root]
    | |-rails.gemspec         [rails gem located here]
    |~actionpack
    | |-actionpack.gemspec    [actionpack gem located here]
    |~activesupport
    | |-activesupport.gemspec [activesupport gem located here]
    ...

To install a gem located in a git repository, bundler changes to
the directory containing the gemspec, runs `gem build name.gemspec`
and then installs the resulting gem. The `gem build` command,
which comes standard with Rubygems, evaluates the `.gemspec` in
the context of the directory in which it is located.

### PATH (:path)

You can specify that a gem is located in a particular location
on the file system. Relative paths are resolved relative to the
directory containing the `Gemfile`.

Similar to the semantics of the `:git` option, the `:path`
option requires that the directory in question either contains
a `.gemspec` for the gem, or that you specify an explicit
version that bundler should use.

Unlike `:git`, bundler does not compile C extensions for
gems specified as paths.

    gem "rails", :path => "vendor/rails"

## BLOCK FORM OF GIT, PATH, GROUP and PLATFORMS

The `:git`, `:path`, `:group`, and `:platforms` options may be
applied to a group of gems by using block form.

    git "git://github.com/rails/rails.git" do
      gem "activesupport"
      gem "actionpack"
    end

    platforms :ruby do
      gem "ruby-debug"
      gem "sqlite3-ruby"
    end

    group :development do
      gem "wirble"
      gem "faker"
    end

In the case of the `git` block form, the `:ref`, `:branch`, `:tag`,
and `:submodules` options may be passed to the `git` method, and
all gems in the block will inherit those options.

## GEMSPEC (#gemspec)

If you wish to use Bundler to help install dependencies for a gem while it is
being developed, use the `gemspec` method to pull in the dependencies listed in
the `.gemspec` file.

The `gemspec` method adds any runtime dependencies as gem requirements in the
default group. It also adds development dependencies as gem requirements in the
`development` group. Finally, it adds a gem requirement on your project (`:path
=> '.'`). In conjunction with `Bundler.setup`, this allows you to require project
files in your test code as you would if the project were installed as a gem; you
need not manipulate the load path manually or require project files via relative
paths.

The `gemspec` method supports optional `:path`, `:name`, and `:development_group`
options, which control where bundler looks for the `.gemspec`, what named
`.gemspec` it uses (if more than one is present), and which group development
dependencies are included in.

## SOURCE PRIORITY

When attempting to locate a gem to satisfy a gem requirement,
bundler uses the following priority order:

  1. The source explicitly attached to the gem (using `:path` or `:git`)
  2. For implicit gems (dependencies of explicit gems), any git or path
     repository otherwise declared. This results in bundler prioritizing the
     ActiveSupport gem from the Rails git repository over ones from
     `rubygems.org`
  3. The sources specified via `source`, in the order in which they were
     declared in the `Gemfile`.