There is a note in the documentation to `Reflection::GetRepeatedFieldRef()`
about file `net/proto2/public/reflection.h` which contains a definition of
`RepeatedFieldRef`. Since there are few places in code with rewrite of
`net...` path to `google/protobuf/...` it looks like the first one is a
legacy path and should be renamed to `google/protobuf` in documentation
as well.
FieldDescriptor.HasPresence returns true if both ClearValue and HasValue (on the accessor) can be expected to work. Some fields have a working ClearValue, but no HasValue; HasPresence returns false for those fields.
Generally:
- Extension fields have presence if and only if they're singular
- Repeated fields do not support presence
- Map fields do not support presence
- Message fields support presence
- Oneof fields support presence (this includes synthetic oneof fields, so that covers proto3 optional singular fields)
- Proto2 singular primitive fields support presence
- Proto3 singular primitive fields do not support presence (unless they're in a oneof, covered above)
This is a breaking change in terms of proto2 code generation: users who were previously using these members will have to change to null checks for message fields.
After toying with removing Has/Clear for proto2 oneof fields, I've left them alone in this commit, for consistency with other languages. The inconsistency between proto2 and proto3 won't come up here, because proto3 oneof fields can never be explicitly optional.
Fixes#7395.
- Bump the version marker in the generated code.
- Set the flag to say clear on zero is known.
- Set clear on zero for proto3 optional fields that aren't tagged as optional.
- Also tweak the call from some C generated code to use different apis with
better validation.
- Mark the ObjC generator as supporting the proto3 optional feature.
- Regenerate the WKTs to get the new flags.
- With the new flags, the syntax isn't needed, so don't pass it.
- To keep library binary compatibility, rename the helpers since one
"Internal" method was called from generated code. Keep a shim with
the old signature to support those generated sources.
- Add a Descriptor flag to capture if the field should clear on being zeroed.
- Update the runtime to use the new clear on zero flag.
- Add a flag on message initialization to indicate the sources were generated
with/without this support so the runtime can backfill the flag for older
generated sources.
