Raised by Gem::Resolver when a Gem::Dependency::Conflict reaches the toplevel. Indicates which dependencies were incompatible through conflict and conflicting_dependencies
Raised when attempting to uninstall a gem that isn’t in GEM_HOME.
Raised when removing a gem with the uninstall command fails
Raised by the DependencyInstaller when a specific gem cannot be found
Raised by Gem::Resolver when dependencies conflict and create the inability to find a valid possible spec for a request.
Signals that a remote operation cannot be conducted, probably due to not being connected (or just not finding host).
Raised when a gem dependencies file specifies a ruby version that does not match the current version.
Raised by Resolver when a dependency requests a gem for which there is no spec.
The installer installs the files contained in the .gem into the Gem.home.
Gem::Installer does the work of putting files in all the right places on the filesystem including unpacking the gem into its gem dir, installing the gemspec in the specifications dir, storing the cached gem in the cache dir, and installing either wrappers or symlinks for executables.
The installer invokes pre and post install hooks. Hooks can be added either through a rubygems_plugin.rb file in an installed gem or via a rubygems/defaults/#{RUBY_ENGINE}.rb or rubygems/defaults/operating_system.rb file. See Gem.pre_install and Gem.post_install for details.
Example using a Gem::Package
Builds a .gem file given a Gem::Specification. A .gem file is a tarball which contains a data.tar.gz, metadata.gz, checksums.yaml.gz and possibly signatures.
require 'rubygems' require 'rubygems/package' spec = Gem::Specification.new do |s| s.summary = "Ruby based make-like utility." s.name = 'rake' s.version = PKG_VERSION s.requirements << 'none' s.files = PKG_FILES s.description = <<-EOF Rake is a Make-like program implemented in Ruby. Tasks and dependencies are specified in standard Ruby syntax. EOF end Gem::Package.build spec
Reads a .gem file.
require 'rubygems' require 'rubygems/package' the_gem = Gem::Package.new(path_to_dot_gem) the_gem.contents # get the files in the gem the_gem.extract_files destination_directory # extract the gem into a directory the_gem.spec # get the spec out of the gem the_gem.verify # check the gem is OK (contains valid gem specification, contains a not corrupt contents archive)
files are the files in the .gem tar file, not the Ruby files in the gem extract_files and contents automatically call verify
Create a package based upon a Gem::Specification. Gem packages, as well as zip files and tar/gzipped packages can be produced by this task.
In addition to the Rake targets generated by Rake::PackageTask, a Gem::PackageTask will also generate the following tasks:
Create a RubyGems package with the given name and version.
Example using a Gem::Specification:
require 'rubygems' require 'rubygems/package_task' spec = Gem::Specification.new do |s| s.summary = "Ruby based make-like utility." s.name = 'rake' s.version = PKG_VERSION s.requirements << 'none' s.files = PKG_FILES s.description = <<-EOF Rake is a Make-like program implemented in Ruby. Tasks and dependencies are specified in standard Ruby syntax. EOF end Gem::PackageTask.new(spec) do |pkg| pkg.need_zip = true pkg.need_tar = true end
RemoteFetcher handles the details of fetching gems and gem information from a remote source.
The Version class processes string versions into comparable values. A version string should normally be a series of numbers separated by periods. Each part (digits separated by periods) is considered its own number, and these are used for sorting. So for instance, 3.10 sorts higher than 3.2 because ten is greater than two.
If any part contains letters (currently only a-z are supported) then that version is considered prerelease. Versions with a prerelease part in the Nth part sort less than versions with N-1 parts. Prerelease parts are sorted alphabetically using the normal Ruby string sorting rules. If a prerelease part contains both letters and numbers, it will be broken into multiple parts to provide expected sort behavior (1.0.a10 becomes 1.0.a.10, and is greater than 1.0.a9).
Prereleases sort between real releases (newest to oldest):
1.0
1.0.b1
1.0.a.2
0.9
If you want to specify a version restriction that includes both prereleases and regular releases of the 1.x series this is the best way:
s.add_dependency 'example', '>= 1.0.0.a', '< 2.0.0'
Users expect to be able to specify a version constraint that gives them some reasonable expectation that new versions of a library will work with their software if the version constraint is true, and not work with their software if the version constraint is false. In other words, the perfect system will accept all compatible versions of the library and reject all incompatible versions.
Libraries change in 3 ways (well, more than 3, but stay focused here!).
The change may be an implementation detail only and have no effect on the client software.
The change may add new features, but do so in a way that client software written to an earlier version is still compatible.
The change may change the public interface of the library in such a way that old software is no longer compatible.
Some examples are appropriate at this point. Suppose I have a Stack class that supports a push and a pop method.
Switch from an array based implementation to a linked-list based implementation.
Provide an automatic (and transparent) backing store for large stacks.
Add a depth method to return the current depth of the stack.
Add a top method that returns the current top of stack (without changing the stack).
Change push so that it returns the item pushed (previously it had no usable return value).
Changes pop so that it no longer returns a value (you must use top to get the top of the stack).
Rename the methods to push_item and pop_item.
Rational Versioning Versions shall be represented by three non-negative integers, separated by periods (e.g. 3.1.4). The first integers is the “major” version number, the second integer is the “minor” version number, and the third integer is the “build” number.
A category 1 change (implementation detail) will increment the build number.
A category 2 change (backwards compatible) will increment the minor version number and reset the build number.
A category 3 change (incompatible) will increment the major build number and reset the minor and build numbers.
Any “public” release of a gem should have a different version. Normally that means incrementing the build number. This means a developer can generate builds all day long, but as soon as they make a public release, the version must be updated.
Let’s work through a project lifecycle using our Stack example from above.
Version 0.0.1
The initial Stack class is release.
Version 0.0.2
Switched to a linked=list implementation because it is cooler.
Version 0.1.0
Added a depth method.
Version 1.0.0
Added top and made pop return nil (pop used to return the old top item).
Version 1.1.0
push now returns the value pushed (it used it return nil).
Version 1.1.1
Fixed a bug in the linked list implementation.
Version 1.1.2
Fixed a bug introduced in the last fix.
Client A needs a stack with basic push/pop capability. They write to the original interface (no top), so their version constraint looks like:
gem 'stack', '>= 0.0'
Essentially, any version is OK with Client A. An incompatible change to the library will cause them grief, but they are willing to take the chance (we call Client A optimistic).
Client B is just like Client A except for two things: (1) They use the depth method and (2) they are worried about future incompatibilities, so they write their version constraint like this:
gem 'stack', '~> 0.1'
The depth method was introduced in version 0.1.0, so that version or anything later is fine, as long as the version stays below version 1.0 where incompatibilities are introduced. We call Client B pessimistic because they are worried about incompatible future changes (it is OK to be pessimistic!).
Version Catastrophe: From: www.zenspider.com/ruby/2008/10/rubygems-how-to-preventing-catastrophe.html
Let’s say you’re depending on the fnord gem version 2.y.z. If you specify your dependency as “>= 2.0.0” then, you’re good, right? What happens if fnord 3.0 comes out and it isn’t backwards compatible with 2.y.z? Your stuff will break as a result of using “>=”. The better route is to specify your dependency with an “approximate” version specifier (“~>”). They’re a tad confusing, so here is how the dependency specifiers work:
Specification From ... To (exclusive) ">= 3.0" 3.0 ... ∞ "~> 3.0" 3.0 ... 4.0 "~> 3.0.0" 3.0.0 ... 3.1 "~> 3.5" 3.5 ... 4.0 "~> 3.5.0" 3.5.0 ... 3.6 "~> 3" 3.0 ... 4.0
For the last example, single-digit versions are automatically extended with a zero to give a sensible result.
Given a set of Gem::Dependency objects as needed and a way to query the set of available specs via set, calculates a set of ActivationRequest objects which indicate all the specs that should be activated to meet the all the requirements.
S3URISigner implements AWS SigV4 for S3 Source to avoid a dependency on the aws-sdk-* gems More on AWS SigV4: docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html
SpecFetcher handles metadata updates from remote gem repositories.
An Uninstaller.
The uninstaller fires pre and post uninstall hooks. Hooks can be added either through a rubygems_plugin.rb file in an installed gem or via a rubygems/defaults/#{RUBY_ENGINE}.rb or rubygems/defaults/operating_system.rb file. See Gem.pre_uninstall and Gem.post_uninstall for details.
The UriFormatter handles URIs from user-input and escaping.
uf = Gem::UriFormatter.new 'example.com' p uf.normalize #=> 'http://example.com'
This class is useful for exploring contents before and after a block
It searches above and below the passed in block to match for whatever criteria you give it:
Example:
def dog # 1
puts "bark" # 2
puts "bark" # 3
end # 4
scan = AroundBlockScan.new(
code_lines: code_lines
block: CodeBlock.new(lines: code_lines[1])
)
scan.scan_while { true }
puts scan.before_index # => 0
puts scan.after_index # => 3
This class is responsible for taking a code block that exists at a far indentaion and then iteratively increasing the block so that it captures everything within the same indentation block.
def dog puts "bow" puts "wow" end
block = BlockExpand.new(code_lines: code_lines)
.call(CodeBlock.new(lines: code_lines[1]))
puts block.to_s # => puts “bow”
puts "wow"
Once a code block has captured everything at a given indentation level then it will expand to capture surrounding indentation.
block = BlockExpand.new(code_lines: code_lines)
.call(block)
block.to_s # => def dog
puts "bow" puts "wow" end