Version: build-in devel version comparisons

The heuristic used by the default version comparison is simple. A
version string is scanned for strings of digits, split into an array of
these strings, and then an element-wise comparison is done.

This fails when presented with something like

  Version.new("1.0.0beta7") <=> Version.new("1.0.0")

because the first three digits match, and the fourth digit of the
receiver (7) is greater than the assumed fourth digit of the parameter
(0).

Fix this by defining an element-wise comparator on a new VersionElement
class. This allows us to correctly compare "alpha", "beta", and "rc"
style version strings, and keeps the logic out of the main version
comparison.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

2 files changed, 71 insertions, 13 deletions

diff --git a/Library/Homebrew/test/test_versions.rb b/Library/Homebrew/test/test_versions.rb
index 972ce130b..9811db57e 100644
--- a/Library/Homebrew/test/test_versions.rb
+++ b/Library/Homebrew/test/test_versions.rb
@@ -23,6 +23,12 @@ class VersionComparisonTests < Test::Unit::TestCase
     assert_version_comparison 'HEAD', '==', 'HEAD'
     assert_version_comparison 'HEAD', '>', '1.2.3'
     assert_version_comparison '1.2.3', '<', 'HEAD'
+    assert_version_comparison '3.2.0b4', '<', '3.2.0'
+    assert_version_comparison '1.0beta6', '<', '1.0b7'
+    assert_version_comparison '1.0b6', '<', '1.0beta7'
+    assert_version_comparison '1.1alpha4', '<', '1.1beta2'
+    assert_version_comparison '1.1beta2', '<', '1.1rc1'
+    assert_nil Version.new('1.0') <=> 'foo'
   end
 
   def test_macos_version_comparison
diff --git a/Library/Homebrew/version.rb b/Library/Homebrew/version.rb
index 30e41392a..01053012f 100644
--- a/Library/Homebrew/version.rb
+++ b/Library/Homebrew/version.rb
@@ -1,3 +1,38 @@
+class VersionElement
+  include Comparable
+
+  attr_reader :elem
+
+  def initialize elem
+    elem = elem.to_s.downcase
+    @elem = case elem
+      when 'a', 'alpha' then 'alpha'
+      when 'b', 'beta' then 'beta'
+      when /\d+/ then elem.to_i
+      else elem
+      end
+  end
+
+  def <=>(other)
+    return unless other.is_a? VersionElement
+    return -1 if string? and other.numeric?
+    return 1 if numeric? and other.string?
+    return elem <=> other.elem
+  end
+
+  def to_s
+    @elem.to_s
+  end
+
+  def string?
+    @elem.is_a? String
+  end
+
+  def numeric?
+    @elem.is_a? Numeric
+  end
+end
+
 class Version
   include Comparable
 
@@ -11,30 +46,47 @@ class Version
     @detected_from_url
   end
 
+  def to_a
+    @array ||= @version.scan(/\d+|[a-zA-Z]+/).map { |e| VersionElement.new(e) }
+  end
+
   def head?
     @version == 'HEAD'
   end
 
-  def nums
-    @version.scan(/\d+/).map { |d| d.to_i }
+  def devel?
+    alpha? or beta? or rc?
+  end
+
+  def alpha?
+    to_a.any? { |e| e.to_s == 'alpha' }
+  end
+
+  def beta?
+    to_a.any? { |e| e.to_s == 'beta' }
+  end
+
+  def rc?
+    to_a.any? { |e| e.to_s == 'rc' }
   end
 
   def <=>(other)
-    return nil unless other.is_a? Version
-    return 0 if self.head? and other.head?
-    return 1 if self.head? and not other.head?
-    return -1 if not self.head? and other.head?
-    return 1 if other.nil?
+    # Return nil if objects aren't comparable
+    return unless other.is_a? Version
+    # Versions are equal if both are HEAD
+    return  0 if head? and other.head?
+    # HEAD is greater than any numerical version
+    return  1 if head? and not other.head?
+    return -1 if not head? and other.head?
 
-    snums = self.nums
-    onums = other.nums
+    stuple, otuple = to_a, other.to_a
 
-    count = [snums.length, onums.length].max
+    max = [stuple.length, otuple.length].max
 
-    snums.fill(0, snums.length, count - snums.length)
-    onums.fill(0, onums.length, count - onums.length)
+    stuple.fill(VersionElement.new(0), stuple.length, max - stuple.length)
+    otuple.fill(VersionElement.new(0), otuple.length, max - otuple.length)
 
-    snums <=> onums
+    stuple <=> otuple
   end
 
   def to_s