Allow ffi.metatype to fail so that "busted" unit tests work

On Github we run unit tests inside "busted". At the start of each test "busted" does some sort of trick (clearing package.loaded)? Which causes "require" to run again for all lua files. This breaks ffi.metatype with error "cannot change a protected metatable" if it is called twice with a single type name, since this is true global state. To work around this this patch wraps ffi.metatype calls in a xpcall() so that failure is silently ignored.

modules/bound2.lua

@@ -160,7 +160,9 @@ function bound2_mt.__call(_, a, b)
 end
 
 if status then
-	ffi.metatype(new, bound2_mt)
+	xpcall(function() -- Allow this to silently fail; assume failure means someone messed with package.loaded
+		ffi.metatype(new, bound2_mt)
+	end, function() end)
 end
 
 return setmetatable({}, bound2_mt)

modules/bound3.lua

@@ -160,7 +160,9 @@ function bound3_mt.__call(_, a, b)
 end
 
 if status then
-	ffi.metatype(new, bound3_mt)
+	xpcall(function() -- Allow this to silently fail; assume failure means someone messed with package.loaded
+		ffi.metatype(new, bound3_mt)
+	end, function() end)
 end
 
 return setmetatable({}, bound3_mt)

modules/mat4.lua

@@ -853,7 +853,9 @@ function mat4_mt.__mul(a, b)
 end
 
 if status then
-	ffi.metatype(new, mat4_mt)
+	xpcall(function() -- Allow this to silently fail; assume failure means someone messed with package.loaded
+		ffi.metatype(new, mat4_mt)
+	end, function() end)
 end
 
 return setmetatable({}, mat4_mt)

modules/quat.lua

@@ -469,7 +469,9 @@ function quat_mt.__pow(a, n)
 end
 
 if status then
-	ffi.metatype(new, quat_mt)
+	xpcall(function() -- Allow this to silently fail; assume failure means someone messed with package.loaded
+		ffi.metatype(new, quat_mt)
+	end, function() end)
 end
 
 return setmetatable({}, quat_mt)

modules/vec2.lua

@@ -381,7 +381,9 @@ function vec2_mt.__div(a, b)
 end
 
 if status then
-	ffi.metatype(new, vec2_mt)
+	xpcall(function() -- Allow this to silently fail; assume failure means someone messed with package.loaded
+		ffi.metatype(new, vec2_mt)
+	end, function() end)
 end
 
 return setmetatable({}, vec2_mt)

modules/vec3.lua

@@ -361,7 +361,9 @@ function vec3_mt.__div(a, b)
 end
 
 if status then
-	ffi.metatype(new, vec3_mt)
+	xpcall(function() -- Allow this to silently fail; assume failure means someone messed with package.loaded
+		ffi.metatype(new, vec3_mt)
+	end, function() end)
 end
 
 return setmetatable({}, vec3_mt)