Merge pull request rails#54341 from fatkodima/enumerable-sole-infinite-collections

Fix `Enumerable#sole` for infinite collections

Author: fatkodima

activesupport/lib/active_support/core_ext/enumerable.rb

@@ -209,10 +209,22 @@ def in_order_of(key, series, filter: true)
   #   Set.new.sole        # => Enumerable::SoleItemExpectedError: no item found
   #   { a: 1, b: 2 }.sole # => Enumerable::SoleItemExpectedError: multiple items found
   def sole
-    case count
-    when 1   then return first # rubocop:disable Style/RedundantReturn
-    when 0   then raise ActiveSupport::EnumerableCoreExt::SoleItemExpectedError, "no item found"
-    when 2.. then raise ActiveSupport::EnumerableCoreExt::SoleItemExpectedError, "multiple items found"
+    result = nil
+    found = false
+
+    each do |element|
+      if found
+        raise SoleItemExpectedError, "multiple items found"
+      end
+
+      result = element
+      found = true
+    end
+
+    if found
+      result
+    else
+      raise SoleItemExpectedError, "no item found"
     end
   end
 end

activesupport/lib/active_support/core_ext/range.rb

@@ -3,3 +3,4 @@
 require "active_support/core_ext/range/conversions"
 require "active_support/core_ext/range/compare_range"
 require "active_support/core_ext/range/overlap"
+require "active_support/core_ext/range/sole"

activesupport/lib/active_support/core_ext/range/sole.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class Range
+  # Returns the sole item in the range. If there are no items, or more
+  # than one item, raises Enumerable::SoleItemExpectedError.
+  #
+  #   (1..1).sole   # => 1
+  #   (2..1).sole   # => Enumerable::SoleItemExpectedError: no item found
+  #   (..1).sole    # => Enumerable::SoleItemExpectedError: infinite range cannot represent a sole item
+  def sole
+    if self.begin.nil? || self.end.nil?
+      raise ActiveSupport::EnumerableCoreExt::SoleItemExpectedError, "infinite range '#{inspect}' cannot represent a sole item"
+    end
+
+    super
+  end
+end

activesupport/test/core_ext/enumerable_test.rb

@@ -398,6 +398,7 @@ def test_sole
     assert_equal 1, GenericEnumerable.new([1]).sole
     assert_raise(expected_raise) { GenericEnumerable.new([1, 2]).sole }
     assert_raise(expected_raise) { GenericEnumerable.new([1, nil]).sole }
+    assert_raise(expected_raise) { GenericEnumerable.new(1..).sole }
   end
 
   def test_doesnt_bust_constant_cache

activesupport/test/core_ext/range_ext_test.rb

@@ -287,4 +287,16 @@ def test_date_time_with_step
     datetime = DateTime.now
     assert(((datetime - 1.hour)..datetime).step(1) { })
   end
+
+  def test_sole
+    assert_equal 1, (1..1).sole
+
+    assert_raises(Enumerable::SoleItemExpectedError, match: "no item found") do
+      (2..1).sole
+    end
+
+    assert_raises(Enumerable::SoleItemExpectedError, match: "infinite range '..1' cannot represent a sole item") do
+      (..1).sole
+    end
+  end
 end