[VersionRanges] Say that != x, = x is empty

2 files changed, 47 insertions, 3 deletions

diff --git a/lib/bundler/version_ranges.rb b/lib/bundler/version_ranges.rb
index 6eca976ee8..3470df7742 100644
--- a/lib/bundler/version_ranges.rb
+++ b/lib/bundler/version_ranges.rb
@@ -26,6 +26,12 @@ module Bundler
       def empty?
         left.version == right.version && !(left.inclusive && right.inclusive)
       end
+
+      def single?
+        left.version == right.version
+      end
+
+      UNIVERSAL = ReqR.new(ReqR::Endpoint.new(Gem::Version.new("0.a"), true), ReqR::Endpoint.new(ReqR::INFINITY, false)).freeze
     end
 
     def self.for_many(requirements)
@@ -46,17 +52,18 @@ module Bundler
         when "<" then ReqR.new(ReqR::Endpoint.new(ReqR::ZERO, true), ReqR::Endpoint.new(v, false))
         when "<=" then ReqR.new(ReqR::Endpoint.new(ReqR::ZERO, true), ReqR::Endpoint.new(v, true))
         when "~>" then ReqR.new(ReqR::Endpoint.new(v, true), ReqR::Endpoint.new(v.bump, false))
+        else raise "unknown version op #{op} in requirement #{requirement}"
         end
       end.uniq
       ranges, neqs = ranges.partition {|r| !r.is_a?(NEq) }
-      ranges << ReqR.new(ReqR::Endpoint.new(Gem::Version.new("0.a"), true), ReqR::Endpoint.new(ReqR::INFINITY, false)) if ranges.empty?
 
-      [ranges.sort_by {|range| [range.left.version, range.left.inclusive ? 0 : 1] }, neqs]
+      [ranges.sort_by {|range| [range.left.version, range.left.inclusive ? 0 : 1] }, neqs.map(&:version)]
     end
 
     def self.empty?(ranges, neqs)
-      !ranges.reduce do |last_range, curr_range|
+      !ranges.reduce(ReqR::UNIVERSAL) do |last_range, curr_range|
         next false unless last_range
+        next false if curr_range.single? && neqs.include?(curr_range.left.version)
         next curr_range if last_range.right.version == ReqR::INFINITY
         case last_range.right.version <=> curr_range.left.version
         when 1 then next curr_range
diff --git a/spec/bundler/version_ranges_spec.rb b/spec/bundler/version_ranges_spec.rb
new file mode 100644
index 0000000000..f746aa88ad
--- /dev/null
+++ b/spec/bundler/version_ranges_spec.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+require "spec_helper"
+require "bundler/version_ranges"
+
+RSpec.describe Bundler::VersionRanges do
+  describe ".empty?" do
+    shared_examples_for "empty?" do |exp, *req|
+      it "returns #{exp} for #{req}" do
+        r = Gem::Requirement.new(*req)
+        ranges = described_class.for(r)
+        expect(described_class.empty?(*ranges)).to eq(exp), "expected `#{r}` #{exp ? "" : "not "}to be empty"
+      end
+    end
+
+    include_examples "empty?", false
+    include_examples "empty?", false, "!= 1"
+    include_examples "empty?", false, "!= 1", "= 2"
+    include_examples "empty?", false, "!= 1", "> 1"
+    include_examples "empty?", false, "!= 1", ">= 1"
+    include_examples "empty?", false, "= 1", ">= 0.1", "<= 1.1"
+    include_examples "empty?", false, "= 1", ">= 1", "<= 1"
+    include_examples "empty?", false, "= 1", "~> 1"
+    include_examples "empty?", false, ">= 0.z", "= 0"
+    include_examples "empty?", false, ">= 0"
+    include_examples "empty?", false, ">= 1.0.0", "< 2.0.0"
+    include_examples "empty?", false, "~> 1"
+    include_examples "empty?", false, "~> 2.0", "~> 2.1"
+    include_examples "empty?", true, "!= 1", "< 2", "> 2"
+    include_examples "empty?", true, "!= 1", "<= 1", ">= 1"
+    include_examples "empty?", true, "< 2", "> 2"
+    include_examples "empty?", true, "= 1", "!= 1"
+    include_examples "empty?", true, "= 1", "= 2"
+    include_examples "empty?", true, "= 1", "~> 2"
+    include_examples "empty?", true, ">= 0", "<= 0.a"
+    include_examples "empty?", true, "~> 2.0", "~> 3"
+  end
+end