[Tests] add tests for disallow_unknown_fields

.gitignore

@@ -2,3 +2,4 @@
 *_easyjson.go
 *.iml
 .idea
+*.swp

Makefile

@@ -37,6 +37,7 @@ generate: root build
 	.root/bin/easyjson .root/src/$(PKG)/tests/named_type.go
 	.root/bin/easyjson .root/src/$(PKG)/tests/custom_map_key_type.go
 	.root/bin/easyjson .root/src/$(PKG)/tests/embedded_type.go
+	.root/bin/easyjson -disallow_unknown_fields .root/src/$(PKG)/tests/disallow_unknown.go
 
 test: generate root
 	go test \

README.md

@@ -53,6 +53,8 @@ Usage of easyjson:
         use lowerCamelCase instead of CamelCase by default
   -stubs
     	only generate stubs for marshaler/unmarshaler funcs
+  -disallow_unknown_fields
+        return error if some unknown field in json occured
 ```
 
 Using `-all` will generate marshalers/unmarshalers for all Go structs in the

tests/basic_test.go

@@ -232,3 +232,11 @@ func TestUnmarshalStructWithEmbeddedPtrStruct(t *testing.T) {
 		t.Errorf("easyjson.Unmarshal() = %#v; want %#v", s, structWithInterfaceValueFilled)
 	}
 }
+
+func TestDisallowUnknown(t *testing.T) {
+	var d DisallowUnknown
+	err := easyjson.Unmarshal([]byte(disallowUnknownString), &d)
+	if err == nil {
+		t.Error("want error, got nil")
+	}
+}

tests/disallow_unknown.go

@@ -0,0 +1,8 @@
+package tests
+
+//easyjson:json
+type DisallowUnknown struct {
+	FieldOne string `json:"field_one"`
+}
+
+var disallowUnknownString = `{"field_one": "one", "field_two": "two"}`