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.
Prereleases sort between real releases (newest to oldest):
1.0
1.0.b
1.0.a
0.9
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.
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 for himself, but as soon as he/she makes 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. He writes to the original interface (no top), so his version constraint looks like:
gem 'stack', '~> 0.0'
Essentially, any version is OK with Client A. An incompatible change to the library will cause him grief, but he is willing to take the chance (we call Client A optimistic).
Client B is just like Client A except for two things: (1) He uses the depth method and (2) he is worried about future incompatibilities, so he writes his 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 he is worried about incompatible future changes (it is OK to be pessimistic!).
From: blog.zenspider.com/2008/10/rubygems-howto-preventing-cata.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 a “spermy” 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
True if the version string matches RubyGems’ requirements.
# File lib/rubygems/version.rb, line 155 155: def self.correct? version 156: version.to_s =~ ANCHORED_VERSION_PATTERN 157: end
Factory method to create a Version object. Input may be a Version or a String. Intended to simplify client code.
ver1 = Version.create('1.3.17') # -> (Version object) ver2 = Version.create(ver1) # -> (ver1) ver3 = Version.create(nil) # -> nil
# File lib/rubygems/version.rb, line 167 167: def self.create input 168: if input.respond_to? :version then 169: input 170: elsif input.nil? then 171: nil 172: else 173: new input 174: end 175: end
Constructs a Version from the version string. A version string is a series of digits or ASCII letters separated by dots.
# File lib/rubygems/version.rb, line 181 181: def initialize version 182: raise ArgumentError, "Malformed version number string #{version}" unless 183: self.class.correct?(version) 184: 185: @version = version.to_s 186: @version.strip! 187: 188: segments # prime @segments 189: end
Compares this version with other returning -1, 0, or 1 if the other version is larger, the same, or smaller than this one.
# File lib/rubygems/version.rb, line 290 290: def <=> other 291: return 1 unless other # HACK: comparable with nil? why? 292: return nil unless self.class === other 293: 294: lhsize = segments.size 295: rhsize = other.segments.size 296: limit = (lhsize > rhsize ? lhsize : rhsize) - 1 297: 298: 0.upto(limit) do |i| 299: lhs, rhs = segments[i] || 0, other.segments[i] || 0 300: 301: return 1 if String === lhs && Numeric === rhs 302: return 1 if Numeric === lhs && String === rhs 303: return lhs <=> rhs if lhs != rhs 304: end 305: 306: return 0 307: 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.b2 => 5.4, are ignored.
# File lib/rubygems/version.rb, line 197 197: def bump 198: segments = self.segments.dup 199: segments.pop while segments.any? { |s| String === s } 200: segments.pop if segments.size > 1 201: 202: segments[1] = segments[1].succ 203: self.class.new segments.join(".") 204: 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 lib/rubygems/version.rb, line 226 226: def marshal_dump 227: [version] 228: end
Load custom marshal format. It’s a string for backwards (RubyGems 1.3.5 and earlier) compatibility.
# File lib/rubygems/version.rb, line 234 234: def marshal_load array 235: initialize array[0] 236: end
A version is considered a prerelease if it contains a letter.
# File lib/rubygems/version.rb, line 241 241: def prerelease? 242: @prerelease ||= segments.any? { |s| String === s } 243: end
The release for this version (e.g. 1.2.0.a -> 1.2.0). Non-prerelease versions return themselves.
# File lib/rubygems/version.rb, line 253 253: def release 254: return self unless prerelease? 255: 256: segments = self.segments.dup 257: segments.pop while segments.any? { |s| String === s } 258: self.class.new segments.join('.') 259: end
A recommended version for use with a ~> Requirement.
# File lib/rubygems/version.rb, line 276 276: def spermy_recommendation 277: segments = self.segments.dup 278: 279: segments.pop while segments.any? { |s| String === s } 280: segments.pop while segments.size > 2 281: segments.push 0 while segments.size < 2 282: 283: "~> #{segments.join(".")}" 284: end
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