Fix conversion from range to slice

Author: mrkn

ext/pycall/pycall.c

@@ -1778,7 +1778,16 @@ pycall_pyslice_from_ruby(VALUE obj)
   }
 
   if (!exclude_end) {
-    end = SSIZET2NUM(NUM2SSIZET(end) + 1); /* TODO: limit check */
+    ssize_t end_i = NUM2SSIZET(end);
+    switch (end_i) {
+      case -1:
+        end = Qnil;
+        break;
+
+      default:
+        end = SSIZET2NUM(end_i + 1); /* TODO: limit check */
+        break;
+    }
   }
 
   pystart = pycall_pyobject_from_ruby(begin);

spec/pycall/pyobject_wrapper_spec.rb

@@ -146,6 +146,10 @@ module PyCall
       context 'when the given index is a Range' do
         specify do
           list = PyCall::List.new([*1..10])
+          expect(list[0..0]).to eq(PyCall::List.new([1]))
+          expect(list[0...0]).to eq(PyCall::List.new([]))
+          expect(list[0..-1]).to eq(PyCall::List.new([*1..10]))
+          expect(list[0...-1]).to eq(PyCall::List.new([*1..9]))
           expect(list[1..-2]).to eq(PyCall::List.new([*2..9]))
           expect(list[1...-2]).to eq(PyCall::List.new([*2..8]))
         end
@@ -154,6 +158,7 @@ module PyCall
       context 'when the given index is an Enumerable that is created by Range#step' do
         specify do
           list = PyCall::List.new([*1..10])
+          expect(list[(1..-1).step(2)]).to eq(PyCall::List.new([2, 4, 6, 8, 10]))
           expect(list[(1..-2).step(2)]).to eq(PyCall::List.new([2, 4, 6, 8]))
         end
       end