make spec.optional check explicitly for nil

Author: atomicptr

spec.lua

@@ -122,10 +122,11 @@ end
 ---@return fun(value: any): boolean
 function M.optional(spec)
     return function(value)
-        if value then
-            return spec(value)
+        -- if no value is specified return true!
+        if value == nil then
+            return true
         end
-        return true
+        return spec(value)
     end
 end
 

spec_test.lua

@@ -47,6 +47,7 @@ describe("spec.lua", function()
         assert.True(spec.optional(spec.string) "Hello, World")
         assert.True(spec.optional(spec.string)(nil))
         assert.False(spec.optional(spec.string)(true))
+        assert.False(spec.optional(spec.string)(false))
     end)
 
     it("spec.all_of", function()