proto: use UnmarshalState

The UnmarshalState method provides information about whether the
message was initialized or not. Checking that bit saves performance
needing to verify again.

Generated files change because of newer versions of dependencies.

Change-Id: I1c1e99b7e28da5959d083ea8652b5fdc8e6c3124
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/220500
Reviewed-by: Damien Neil <[email protected]>

Author: dsnet

go.mod

@@ -3,6 +3,6 @@ module github.com/golang/protobuf
 go 1.9
 
 require (
-	github.com/google/go-cmp v0.3.1
-	google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd
+	github.com/google/go-cmp v0.4.0
+	google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64
 )

go.sum

@@ -1,5 +1,10 @@
+github.com/golang/protobuf v1.4.0-rc.1/go.mod h1:ceaxUfeHdC40wWswd/P6IGgMaK3YpKi5j83Wpe3EHw8=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
-github.com/google/go-cmp v0.3.1 h1:Xye71clBPdm5HgqGwUkwhbynsUJZhDbS20FvLhQ2izg=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
-google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd h1:zSMqFwpTkfj+1nNFgmgu4B+Qv5Kpf4jpd11lCmHKuwQ=
+github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=
+github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 google.golang.org/protobuf v0.0.0-20200109180630-ec00e32a8dfd/go.mod h1:DFci5gLYBciE7Vtevhsrf46CRTquxDuWsQurQQe4oz8=
+google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64 h1:BhpvsYSxWvxATQJYrD9UKX1U3jo+Bxq195IzJGtyh40=
+google.golang.org/protobuf v0.0.0-20200221191635-4d8936d0db64/go.mod h1:kwYJMbMJ01Woi6D6+Kah6886xMZcty6N08ah7+eCXa0=

proto/wire.go

@@ -6,6 +6,7 @@ package proto
 
 import (
 	protoV2 "google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/runtime/protoiface"
 	"google.golang.org/protobuf/runtime/protoimpl"
 )
 
@@ -61,12 +62,17 @@ func Unmarshal(b []byte, m Message) error {
 // UnmarshalMerge parses a wire-format message in b and places the decoded results in m.
 func UnmarshalMerge(b []byte, m Message) error {
 	mi := protoimpl.X.ProtoMessageV2Of(m)
-	err := protoV2.UnmarshalOptions{
+	out, err := protoV2.UnmarshalOptions{
 		AllowPartial: true,
 		Merge:        true,
-	}.Unmarshal(b, mi)
+	}.UnmarshalState(mi, protoiface.UnmarshalInput{
+		Buf: b,
+	})
 	if err != nil {
 		return err
 	}
+	if out.Flags&protoiface.UnmarshalInitialized > 0 {
+		return nil
+	}
 	return checkRequiredNotSet(mi)
 }