erb.rb: Add ERB#result_with_hash

[ruby-core:55985] [Feature #8631] [fix GH-1623]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58891 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/erb.rb

@@ -889,6 +889,16 @@ class ERB
     end
   end
 
+  # Render a template on a new toplevel binding with local variables specified
+  # by a Hash object.
+  def result_with_hash(hash)
+    b = new_toplevel
+    hash.each_pair do |key, value|
+      b.local_variable_set(key, value)
+    end
+    result(b)
+  end
+
   ##
   # Returns a new binding each time *near* TOPLEVEL_BINDING for runs that do
   # not specify a binding.

test/erb/test_erb.rb

@@ -564,6 +564,35 @@ EOS
       assert_equal(flag, erb.result)
     end
   end
+
+  def test_result_with_hash
+    erb = @erb.new("<%= foo %>")
+    assert_equal("1", erb.result_with_hash(foo: "1"))
+  end
+
+  def test_result_with_hash_does_not_use_caller_local_variables
+    erb = @erb.new("<%= foo %>")
+    foo = 1
+    assert_raise(NameError) { erb.result_with_hash({}) }
+  end
+
+  def test_result_with_hash_does_not_modify_caller_binding
+    erb = @erb.new("<%= foo %>")
+    erb.result_with_hash(foo: "1")
+    assert_equal(false, binding.local_variable_defined?(:foo))
+  end
+
+  def test_result_with_hash_does_not_modify_toplevel_binding
+    erb = @erb.new("<%= foo %>")
+    erb.result_with_hash(foo: "1")
+    assert_equal(false, TOPLEVEL_BINDING.local_variable_defined?(:foo))
+  end
+
+  # This depends on the behavior that #local_variable_set raises TypeError by invalid key.
+  def test_result_with_hash_with_invalid_keys_raises_type_error
+    erb = @erb.new("<%= 1 %>")
+    assert_raise(TypeError) { erb.result_with_hash({ 1 => "1" }) }
+  end
 end
 
 class TestERBCoreWOStrScan < TestERBCore