1 files changed, 102 insertions, 0 deletions
diff --git a/lib/rubygems/resolver/conflict.rb b/lib/rubygems/resolver/conflict.rb
new file mode 100644
index 0000000000..b081972658
--- /dev/null
+++ b/lib/rubygems/resolver/conflict.rb
@@ -0,0 +1,102 @@
+##
+# Used internally to indicate that a dependency conflicted
+# with a spec that would be activated.
+
+class Gem::Resolver::Conflict
+
+  attr_reader :activated
+
+  attr_reader :dependency
+
+  attr_reader :failed_dep # :nodoc:
+
+  def initialize(dependency, activated, failed_dep=dependency)
+    @dependency = dependency
+    @activated = activated
+    @failed_dep = failed_dep
+  end
+
+  def == other
+    self.class === other and
+      @dependency == other.dependency and
+      @activated  == other.activated  and
+      @failed_dep == other.failed_dep
+  end
+
+  def explain
+    "<Conflict wanted: #{@failed_dep}, had: #{activated.spec.full_name}>"
+  end
+
+  ##
+  # Return the 2 dependency objects that conflicted
+
+  def conflicting_dependencies
+    [@failed_dep.dependency, @activated.request.dependency]
+  end
+
+  ##
+  # Explanation of the conflict used by exceptions to print useful messages
+
+  def explanation
+    activated   = @activated.spec.full_name
+    requirement = @failed_dep.dependency.requirement
+
+    "  Activated %s instead of (%s) via:\n    %s\n" % [
+      activated, requirement, request_path.join(', ')
+    ]
+  end
+
+  def for_spec?(spec)
+    @dependency.name == spec.name
+  end
+
+  def pretty_print q # :nodoc:
+    q.group 2, '[Dependency conflict: ', ']' do
+      q.breakable
+
+      q.text 'activated '
+      q.pp @activated
+
+      q.breakable
+      q.text ' dependency '
+      q.pp @dependency
+
+      q.breakable
+      if @dependency == @failed_dep then
+        q.text ' failed'
+      else
+        q.text ' failed dependency '
+        q.pp @failed_dep
+      end
+    end
+  end
+
+  ##
+  # Path of specifications that requested this dependency
+
+  def request_path
+    current = requester
+    path    = []
+
+    while current do
+      path << current.spec.full_name
+
+      current = current.request.requester
+    end
+
+    path = ['user request (gem command or Gemfile)'] if path.empty?
+
+    path
+  end
+
+  ##
+  # Return the Specification that listed the dependency
+
+  def requester
+    @failed_dep.requester
+  end
+
+end
+
+Gem::Resolver::DependencyConflict = Gem::Resolver::Conflict
+