Add test case for require_file with a usertype

I was having problems with usertypes and require_file, so I figured I
shoudl work in a less complicated testbed than mine, and worked here.
There as not a test case, so I wrote this one.

Additionally, adjusted bootstrap.py to allow for `--lua-version lua53`
syntax since most older linux systems use lua52, its useful to override.

bootstrap.py

@@ -42,6 +42,7 @@ parser.add_argument('--cxx', metavar='<compiler>', help='compiler name to use (d
 parser.add_argument('--cxx-flags', help='additional flags passed to the compiler', default='')
 parser.add_argument('--ci', action='store_true', help=argparse.SUPPRESS)
 parser.add_argument('--testing', action='store_true', help=argparse.SUPPRESS)
+parser.add_argument('--lua-version', help='Lua version, e.g. lua53', default='lua53')
 parser.add_argument('--lua-lib', help='lua library name (without the lib on *nix).', default='lua')
 parser.add_argument('--lua-dir', metavar='<dir>', help='directory lua is in with include and lib subdirectories')
 parser.add_argument('--install-dir', metavar='<dir>', help='directory to install the headers to', default=install_dir);
@@ -82,7 +83,7 @@ if args.lua_dir:
     ldflags.extend(library_includes([os.path.join(args.lua_dir, 'lib')]))
 
 if 'linux' in sys.platform:
-    lua_version = os.environ.get('LUA_VERSION', 'lua53')
+    lua_version = os.environ.get('LUA_VERSION', args.lua_version)
     if re.match(r'lua5[1-3]', lua_version):
         # Using normal lua
         lua_lib = lua_version[:-1] + '.' + lua_version[-1]
@@ -101,7 +102,7 @@ if 'linux' in sys.platform:
     ldflags.extend(libraries([lua_lib]))
 elif 'darwin' in sys.platform:
     # OSX 
-    lua_version = os.environ.get('LUA_VERSION', 'lua53')
+    lua_version = os.environ.get('LUA_VERSION', args.lua_version)
     if re.match(r'lua5[1-3]', lua_version):
         # Using normal lua
         lua_incl = lua_version[:-1] + '.' + lua_version[-1]

tests.cpp

@@ -3,10 +3,13 @@
 
 #include <catch.hpp>
 #include <sol.hpp>
-#include <vector>
+
+#include <fstream>
+#include <iostream>
 #include <map>
 #include <unordered_map>
-#include <iostream>
+#include <vector>
+
 #include "test_stack_guard.hpp"
 
 bool func_opt_ret_bool(sol::optional<int> i) {
@@ -316,6 +319,64 @@ TEST_CASE("object/conversions", "make sure all basic reference types can be made
 	REQUIRE(omn.get_type() == sol::type::nil);
 }
 
+TEST_CASE("state/require_file", "opening files as 'requires'") {
+	static const char FILE_NAME[] = "./tmp_thingy.lua";
+
+	std::fstream file(FILE_NAME, std::ios::out);
+
+	sol::state lua;
+	lua.open_libraries(sol::lib::base);
+
+	SECTION("with usertypes")
+	{
+		struct foo {
+			foo(int bar) : bar(bar) {}
+
+			const int bar;
+		};
+
+		lua.new_usertype<foo>("foo",
+			sol::constructors<sol::types<int>>{},
+			"bar", &foo::bar
+			);
+		
+		file << "return { modfunc = function () return foo.new(221) end }" << std::endl;
+		file.close();
+		
+		const sol::table thingy1 = lua.require_file("thingy", FILE_NAME);
+
+		CHECK(thingy1.valid());
+
+		const foo foo_v = thingy1["modfunc"]();
+
+		int val1 = foo_v.bar;
+
+		CHECK(val1 == 221);
+	}
+
+	SECTION("simple")
+	{
+		file << "return { modfunc = function () return 221 end }" << std::endl;
+		file.close();
+		
+		const sol::table thingy1 = lua.require_file("thingy", FILE_NAME);
+		const sol::table thingy2 = lua.require_file("thingy", FILE_NAME);
+
+		CHECK(thingy1.valid());
+		CHECK(thingy2.valid());
+
+		int val1 = thingy1["modfunc"]();
+		int val2 = thingy2["modfunc"]();
+
+		CHECK(val1 == 221);
+		CHECK(val2 == 221);
+		// must have loaded the same table
+		CHECK(thingy1 == thingy2);
+	}
+
+	std::remove(FILE_NAME);
+}
+
 TEST_CASE("state/require_script", "opening strings as 'requires' clauses") {
 	std::string code = "return { modfunc = function () return 221 end }";