Treat only symbol keys as keyword arguments

If you pass key-value pairs to a method only the keys that are Symbols
will be treated as keyword arguments. If there are optional arguments
the rest of the keys will be passed to the optional one.

Given a method foo(x = {}, y: 1):
* foo('a' => 1) => will work
* foo('a' => 1, :y => 2) => will work
* foo('a' => 1, :b => 2) => will raise ArgumentError unknown keyword: b

Author: edzhelyov

lib/rspec/support/method_signature_verifier.rb

@@ -361,7 +361,14 @@ def unlimited_args?
 
       def split_args(*args)
         kw_args = if @signature.has_kw_args_in?(args)
-                    args.pop.keys
+                    last = args.pop
+                    non_kw_args = last.reject { |k, _| k.is_a?(Symbol) }
+                    if non_kw_args.empty?
+                      last.keys
+                    else
+                      args << non_kw_args
+                      last.select { |k, _| k.is_a?(Symbol) }.keys
+                    end
                   else
                     []
                   end

spec/rspec/support/method_signature_verifier_spec.rb

@@ -384,13 +384,17 @@ def arity_kw(x, y = {}, z:2); end
               expect(valid?(nil, :a => 1)).to eq(false)
             end
 
-            it 'allows Hash containing strings as last argument' do
+            it 'treats symbols as keyword arguments and the rest as optional argument' do
               expect(valid?(nil, 'a' => 1)).to eq(true)
+              expect(valid?(nil, 'a' => 1, :z => 3)).to eq(true)
+              expect(valid?(nil, 'a' => 1, :b => 3)).to eq(false)
+              expect(valid?(nil, 'a' => 1, :b => 2, :z => 3)).to eq(false)
             end
 
             it 'mentions the invalid keyword args in the error', :pending => RSpec::Support::Ruby.jruby? && !RSpec::Support::Ruby.jruby_9000? do
-              expect(error_for(nil, nil, :a => 0)).to \
-                eq("Invalid keyword arguments provided: a")
+              expect(error_for(1, 2, :a => 0)).to eq("Invalid keyword arguments provided: a")
+              expect(error_for(1, :a => 0)).to eq("Invalid keyword arguments provided: a")
+              expect(error_for(1, 'a' => 0, :b => 0)).to eq("Invalid keyword arguments provided: b")
             end
 
             it 'describes invalid arity precisely' do