metadata: move FromOutgoingContextRaw() to internal (#6765)

Co-authored-by: Arvind Bright <arvind.bright100@gmail.com>

internal/internal.go

@@ -189,9 +189,13 @@ var (
 	// the associated watch timer fires. For testing purposes, having this
 	// function makes events more predictable than relying on timer events.
 	TriggerXDSResourceNameNotFoundForTesting any // func(func(xdsresource.Type, string), string, string) error
+
 	// TriggerXDSResourceNotFoundClient invokes the testing xDS Client singleton
 	// to invoke resource not found for a resource type name and resource name.
 	TriggerXDSResourceNameNotFoundClient any // func(string, string) error
+
+	// FromOutgoingContextRaw returns the un-merged, intermediary contents of metadata.rawMD.
+	FromOutgoingContextRaw any // func(context.Context) (metadata.MD, [][]string, bool)
 )
 
 // HealthChecker defines the signature of the client-side LB channel health checking function.

internal/transport/http2_client.go

@@ -59,6 +59,8 @@ import (
 // atomically.
 var clientConnectionCounter uint64
 
+var metadataFromOutgoingContextRaw = internal.FromOutgoingContextRaw.(func(context.Context) (metadata.MD, [][]string, bool))
+
 // http2Client implements the ClientTransport interface with HTTP2.
 type http2Client struct {
 	lastRead  int64 // Keep this field 64-bit aligned. Accessed atomically.
@@ -568,7 +570,7 @@ func (t *http2Client) createHeaderFields(ctx context.Context, callHdr *CallHdr)
 		headerFields = append(headerFields, hpack.HeaderField{Name: "grpc-trace-bin", Value: encodeBinHeader(b)})
 	}
 
-	if md, added, ok := metadata.FromOutgoingContextRaw(ctx); ok {
+	if md, added, ok := metadataFromOutgoingContextRaw(ctx); ok {
 		var k string
 		for k, vv := range md {
 			// HTTP doesn't allow you to set pseudoheaders after non pseudoheaders were set.

metadata/metadata.go

@@ -25,8 +25,14 @@ import (
 	"context"
 	"fmt"
 	"strings"
+
+	"google.golang.org/grpc/internal"
 )
 
+func init() {
+	internal.FromOutgoingContextRaw = fromOutgoingContextRaw
+}
+
 // DecodeKeyValue returns k, v, nil.
 //
 // Deprecated: use k and v directly instead.
@@ -238,16 +244,13 @@ func copyOf(v []string) []string {
 	return vals
 }
 
-// FromOutgoingContextRaw returns the un-merged, intermediary contents of rawMD.
+// fromOutgoingContextRaw returns the un-merged, intermediary contents of rawMD.
 //
 // Remember to perform strings.ToLower on the keys, for both the returned MD (MD
 // is a map, there's no guarantee it's created using our helper functions) and
 // the extra kv pairs (AppendToOutgoingContext doesn't turn them into
 // lowercase).
-//
-// This is intended for gRPC-internal use ONLY. Users should use
-// FromOutgoingContext instead.
-func FromOutgoingContextRaw(ctx context.Context) (MD, [][]string, bool) {
+func fromOutgoingContextRaw(ctx context.Context) (MD, [][]string, bool) {
 	raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
 	if !ok {
 		return nil, nil, false

stream.go

@@ -48,6 +48,8 @@ import (
 	"google.golang.org/grpc/status"
 )
 
+var metadataFromOutgoingContextRaw = internal.FromOutgoingContextRaw.(func(context.Context) (metadata.MD, [][]string, bool))
+
 // StreamHandler defines the handler called by gRPC server to complete the
 // execution of a streaming RPC.
 //
@@ -184,7 +186,7 @@ func newClientStream(ctx context.Context, desc *StreamDesc, cc *ClientConn, meth
 	// when the RPC completes.
 	opts = append([]CallOption{OnFinish(func(error) { cc.idlenessMgr.OnCallEnd() })}, opts...)
 
-	if md, added, ok := metadata.FromOutgoingContextRaw(ctx); ok {
+	if md, added, ok := metadataFromOutgoingContextRaw(ctx); ok {
 		// validate md
 		if err := imetadata.Validate(md); err != nil {
 			return nil, status.Error(codes.Internal, err.Error())