feat: skip explicitly ignored fields

musttag.go

@@ -204,13 +204,19 @@ func (c *checker) checkStruct(styp *types.Struct, tag string) (valid bool) {
 			continue
 		}
 
-		if _, ok := reflect.StructTag(styp.Tag(i)).Lookup(tag); !ok {
+		tagValue, ok := reflect.StructTag(styp.Tag(i)).Lookup(tag)
+		if !ok {
 			// tag is not required for embedded types; see issue #12.
 			if !field.Embedded() {
 				return false
 			}
 		}
 
+		// Do not recurse into ignored fields.
+		if tagValue == "-" {
+			return true
+		}
+
 		if valid := c.checkType(field.Type(), tag); !valid {
 			return false
 		}

testdata/src/tests/tests.go

@@ -149,3 +149,18 @@ func nestedTypeWithInterface() {
 	json.Marshal(Foo{})  // no error
 	json.Marshal(&Foo{}) // no error
 }
+
+func ignoredNestedType() {
+	type Nested struct {
+		NoTag string
+	}
+	type Foo struct {
+		Ignored  Nested `json:"-"`
+		Exported string `json:"exported"`
+	}
+	var foo Foo
+	json.Marshal(foo)    // no error
+	json.Marshal(&foo)   // no error
+	json.Marshal(Foo{})  // no error
+	json.Marshal(&Foo{}) // no error
+}