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'
How Software Changes
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.
Examples of Category 1 changes:
-
Switch from an array based implementation to a linked-list based implementation.
-
Provide an automatic (and transparent) backing store for large stacks.
Examples of Category 2 changes might be:
-
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).
Examples of Category 3 changes might be:
-
Changes
pop
so that it no longer returns a value (you must usetop
to get the top of the stack). -
Rename the methods to
push_item
andpop_item
.
RubyGems 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.
Examples
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 madepop
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!).
Preventing 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.
This is needed for compatibility with older yaml gemspecs.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 173
def self.correct?(version)
nil_versions_are_discouraged! if version.nil?
ANCHORED_VERSION_PATTERN.match?(version.to_s)
end
True if the version
string matches RubyGems’ requirements.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 187
def self.create(input)
if self === input # check yourself before you wreck yourself
input
elsif input.nil?
nil_versions_are_discouraged!
nil
else
new input
end
end
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 221
def initialize(version)
unless self.class.correct?(version)
raise ArgumentError, "Malformed version number string #{version}"
end
# If version is an empty string convert it to 0
version = 0 if version.is_a?(String) && /\A\s*\Z/.match?(version)
@version = version.to_s
# optimization to avoid allocation when given an integer, since we know
# it's to_s won't have any spaces or dashes
unless version.is_a?(Integer)
@version = @version.strip
@version.gsub!("-",".pre.")
end
@version = -@version
@segments = nil
end
Constructs a Version
from the version
string. A version string is a series of digits or ASCII letters separated by dots.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 209
def self.nil_versions_are_discouraged!
unless Gem::Deprecate.skip
warn "nil versions are discouraged and will be deprecated in Rubygems 4"
end
end
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 357
def <=>(other)
return self <=> self.class.new(other) if (String === other) && self.class.correct?(other)
return unless Gem::Version === other
return 0 if @version == other.version || canonical_segments == other.canonical_segments
lhsegments = canonical_segments
rhsegments = other.canonical_segments
lhsize = lhsegments.size
rhsize = rhsegments.size
limit = (lhsize > rhsize ? lhsize : rhsize) - 1
i = 0
while i <= limit
lhs = lhsegments[i] || 0
rhs = rhsegments[i] || 0
i += 1
next if lhs == rhs
return -1 if String === lhs && Numeric === rhs
return 1 if Numeric === lhs && String === rhs
return lhs <=> rhs
end
0
end
Compares this version with other
returning -1, 0, or 1 if the other version is larger, the same, or smaller than this one. Attempts to compare to something that’s not a Gem::Version
or a valid version String
return nil
.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 408
def _segments
# segments is lazy so it can pick up version values that come from
# old marshaled versions, which don't go through marshal_load.
# since this version object is cached in @@all, its @segments should be frozen
@segments ||= partition_segments(@version)
end
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 339
def approximate_recommendation
segments = self.segments
segments.pop while segments.any? {|s| String === s }
segments.pop while segments.size > 2
segments.push 0 while segments.size < 2
recommendation = "~> #{segments.join(".")}"
recommendation += ".a" if prerelease?
recommendation
end
A recommended version for use with a ~> Requirement.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 247
def bump
@@bump[self] ||= begin
segments = self.segments
segments.pop while segments.any? {|s| String === s }
segments.pop if segments.size > 1
segments[-1] = segments[-1].succ
self.class.new segments.join(".")
end
end
Return a new version object where the next to the last revision number is one greater (e.g., 5.3.1 => 5.4).
Pre-release (alpha) parts, e.g, 5.3.1.b.2 => 5.4, are ignored.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 388
def canonical_segments
@canonical_segments ||= begin
# remove trailing 0 segments, using dot or letter as anchor
# may leave a trailing dot which will be ignored by partition_segments
canonical_version = @version.sub(/(?<=[a-zA-Z.])[.0]+\z/, "")
# remove 0 segments before the first letter in a prerelease version
canonical_version.sub!(/(?<=\.|\A)[0.]+(?=[a-zA-Z])/, "") if prerelease?
partition_segments(canonical_version)
end
end
remove trailing zeros segments before first letter or at the end of the version
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 262
def eql?(other)
self.class === other && @version == other.version
end
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 399
def freeze
prerelease?
_segments
canonical_segments
super
end
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 282
def marshal_dump
[@version]
end
Dump only the raw version string, not the complete object. It’s a string for backwards (RubyGems 1.3.5 and earlier) compatibility.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 290
def marshal_load(array)
initialize array[0]
end
Load custom marshal format. It’s a string for backwards (RubyGems 1.3.5 and earlier) compatibility.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 415
def partition_segments(ver)
ver.scan(/\d+|[a-z]+/i).map! do |s|
/\A\d/.match?(s) ? s.to_i : -s
end.freeze
end
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 307
def prerelease?
unless instance_variable_defined? :@prerelease
@prerelease = /[a-zA-Z]/.match?(version)
end
@prerelease
end
A version is considered a prerelease if it contains a letter.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 322
def release
@@release[self] ||= if prerelease?
segments = self.segments
segments.pop while segments.any? {|s| String === s }
self.class.new segments.join(".")
else
self
end
end
The release for this version (e.g. 1.2.0.a -> 1.2.0). Non-prerelease versions return themselves.
# File tmp/rubies/ruby-master/lib/rubygems/version.rb, line 164
def version
@version
end
A string representation of this Version
.