path

Each element is a field number or an index. They form a path from the root FileDescriptorProto to the place where the definition appears. For example, this path: [ 4, 3, 2, 7, 1 ] refers to: file.message_type(3) // 4, 3 .field(7) // 2, 7 .name() // 1 This is because FileDescriptorProto.message_type has field number 4: repeated DescriptorProto message_type = 4; and DescriptorProto.field has field number 2: repeated FieldDescriptorProto field = 2; and FieldDescriptorProto.name has field number 1: optional string name = 1;

Thus, the above path gives the location of a field name. If we removed the last element: [ 4, 3, 2, 7 ] this path refers to the whole field declaration (from the beginning of the label to the terminating semicolon).