galenwarren commented on a change in pull request #304:
URL: https://github.com/apache/flink-statefun/pull/304#discussion_r814945656
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File path: statefun-sdk-go/v3/pkg/statefun/handler.go
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@@ -225,11 +225,10 @@ func (h *handler) invoke(ctx context.Context, toFunction
*protocol.ToFunction) (
var cancel context.CancelFunc
sContext.Context, cancel = context.WithCancel(ctx)
- var caller Address
if invocation.Caller != nil {
Review comment:
If I'm thinking about it right, I think the new unit tests demonstrate
this is working, i.e. they:
* Create an instance of `protocol.ToFunction`, which contains (among other
things) the invocations and associated callers (with the caller populated in
one test and not populated in another test)
* Serialize that `protocol.ToFunction` to a `[]byte` using `proto.Marshal`
* Call `handler.Invoke` passing the serialized `protocol.ToFunction`, which
internally deserializes the `protocol.ToFunction` using `proto.Unmarshal`
before continuing to process it
* Validates that the resulting `statefunContext.caller` (via Context.Caller)
is nil or a not-nil value, according to whether a caller was supplied in the
original `protocol.ToFunction`
So, if a nil caller in the `protocol.ToFunction` were getting deserialized
to a non-nil value via `proto.Unmarshal`, that would cause the
`TestStatefunHandler_WithNoCaller_ContextCallerIsNil` unit test to fail.
Separately, I do a reasonable amount of work with Golang and protobuf, and
while it's true that, in protobuf 3, primitive fields in messages are not
deserialized to nil, embedded *message* fields can be deserialized to nil, as
can repeated values where there are no values. The general rule for protobuf in
Golang, as I understand it, is that fields not specified in a protobuf message
are deserialized to the appropriate zero value in the generated Golang structs;
since nested protobuf messages are generated as *pointers* to structs, the zero
value used in those cases is nil.
There's some discussion of this
[here](https://github.com/golang/protobuf/issues/15); in particular, note:
> When the .proto file specifies syntax="proto3", there are some
differences: Non-repeated fields of non-message type are values instead of
pointers.
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