Fail initialization if an unknown attribute is present

[brianstien]

When initializing a protobuf message object with a hash of attributes, is it possible to fail if an attribute is not a field on the underlying message?

class Foo < Protobuf::Message
  optional :string, :hello, 1
end

# This is normal use
Foo.new(:hello => "world")

# This could fail with an UnknownAttributeError, but does not
Foo.new(:some_random_attribute_that_doesnt_exist => "foobar")

[localshred]

Unsure if you're asking a question or proposing a change...

No, we don't fail when you provide a bogus field on hash initialization. When decoding bytes we don't fail on unknown fields (for obvious reasons) and I believe that behavior has transferred over to initialization with a hash.

[abrandoned]

Not sure if we should "fail"; I looked through the Java and C implementations and it looks like they store unknown attributes (fields) in a map (UnknownFieldSet in C, FieldSet in Java) and allow introspection on the fields that are unknown through methods like is_empty?(), field_count()

if those implementation don't blow-up when unknown fields are encountered then it seems we should follow that path

they do not however generate the assignment methods to assign the value, but during initialization it doesn't look like they stop execution

https://developers.google.com/protocol-buffers/docs/reference/cpp/google.protobuf.unknown_field_set#UnknownFieldSet

will do some more reading and see if anything else stands out