We resisted adding Clone for a while since:
* It is a function that is perfectly suited for generics.
However, generics probably still won't be available in Go for some time
and it is impractical to block addition of this function when it is very
widely used and will be necessary for the v1 to v2 migration.
* In the past, there was no protoreflect.Message.IsValid, so there was
no proper API to detect invalid top-level messages and return them as such.
Since Clone relies on certain properties about proper round-tripping
of ProtoMessage.ProtoReflect <-> Message.Interface, we add a test
in testing/prototest to check for this.
Change-Id: Ic492b68f27b8b88322a6a3fa3a5e492228db79d9
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/213297
Reviewed-by: Damien Neil <dneil@google.com>
A shallow copy of a message is a common operation with over 10k
usages inside Google. However, the semantics of a shallow copy
on the struct is ill-defined and not officially supported by
the generated protobuf API.
To reduce improper usages, add an official implementation of
shallow merging that does something similar where messages, lists,
and maps are shallow copied into the destination if it does not
already have one populated.
In the common case where the destination is empty, this equivalent to:
src.Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
dst.Set(fd, v)
})
if len(src.GetUnknown()) > 0 {
dst.SetUnknown(src.GetUnknown())
}
which is as simple of a shallow copy definition as you can get.
A future CL will add a fast-path implementation of both
deep and shallow merges.
Change-Id: Ic4a5503dd1b11b505738f5e503f97d55997e9418
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/213131
Reviewed-by: Damien Neil <dneil@google.com>
While odd, it is possible to merge a message into itself.
In such a situation, the material impact is that repeated
and unknown fields are duplicated. The previous logic would
inifinite loop since the list iteration logic uses the current
length, but since the current length is ever growing, this loop
will never terminate. Instead, record the list length once
and iterate exactly that many times.
Change-Id: Ief98afa1b20bd950a9c2422d4462b170dbe6fa11
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/196857
Reviewed-by: Damien Neil <dneil@google.com>
Some existing targets (whether correctly or not) rely on it Merge
being safe to call concurrently so long as the set of fields being
merged are disjoint.
Change-Id: I4db9e64efccc7a2d44a5f9b52261b611cce461b0
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/196737
Reviewed-by: Damien Neil <dneil@google.com>
