peer and metadata: Implement the Stringer interface for Peer and Metadata

metadata/metadata.go

@@ -90,6 +90,21 @@ func Pairs(kv ...string) MD {
 	return md
 }
 
+// String implements the Stringer interface for pretty-printing a MD.
+// Ordering of the values is non-deterministic as it ranges over a map.
+func (md MD) String() string {
+	var sb strings.Builder
+	fmt.Fprintf(&sb, "MD{")
+	for k, v := range md {
+		if sb.Len() > 3 {
+			fmt.Fprintf(&sb, ", ")
+		}
+		fmt.Fprintf(&sb, "%s=[%s]", k, strings.Join(v, ", "))
+	}
+	fmt.Fprintf(&sb, "}")
+	return sb.String()
+}
+
 // Len returns the number of items in md.
 func (md MD) Len() int {
 	return len(md)

metadata/metadata_test.go

@@ -22,6 +22,7 @@ import (
 	"context"
 	"reflect"
 	"strconv"
+	"strings"
 	"testing"
 	"time"
 
@@ -338,6 +339,26 @@ func (s) TestAppendToOutgoingContext_FromKVSlice(t *testing.T) {
 	}
 }
 
+func TestStringerMD(t *testing.T) {
+	for _, test := range []struct {
+		md   MD
+		want []string
+	}{
+		{MD{}, []string{"MD{}"}},
+		{MD{"k1": []string{}}, []string{"MD{k1=[]}"}},
+		{MD{"k1": []string{"v1", "v2"}}, []string{"MD{k1=[v1, v2]}"}},
+		{MD{"k1": []string{"v1"}}, []string{"MD{k1=[v1]}"}},
+		{MD{"k1": []string{"v1", "v2"}, "k2": []string{}, "k3": []string{"1", "2", "3"}}, []string{"MD{", "k1=[v1, v2]", "k2=[]", "k3=[1, 2, 3]", "}"}},
+	} {
+		got := test.md.String()
+		for _, want := range test.want {
+			if !strings.Contains(got, want) {
+				t.Fatalf("Metadata string %q is missing %q", got, want)
+			}
+		}
+	}
+}
+
 // Old/slow approach to adding metadata to context
 func Benchmark_AddingMetadata_ContextManipulationApproach(b *testing.B) {
 	// TODO: Add in N=1-100 tests once Go1.6 support is removed.

peer/peer.go

@@ -22,7 +22,9 @@ package peer
 
 import (
 	"context"
+	"fmt"
 	"net"
+	"strings"
 
 	"google.golang.org/grpc/credentials"
 )
@@ -39,6 +41,34 @@ type Peer struct {
 	AuthInfo credentials.AuthInfo
 }
 
+// String ensures the Peer types implements the Stringer interface in order to
+// allow to print a context with a peerKey value effectively.
+func (p *Peer) String() string {
+	if p == nil {
+		return "Peer<nil>"
+	}
+	sb := &strings.Builder{}
+	sb.WriteString("Peer{")
+	if p.Addr != nil {
+		fmt.Fprintf(sb, "Addr: '%s', ", p.Addr.String())
+	} else {
+		fmt.Fprintf(sb, "Addr: <nil>, ")
+	}
+	if p.LocalAddr != nil {
+		fmt.Fprintf(sb, "LocalAddr: '%s', ", p.LocalAddr.String())
+	} else {
+		fmt.Fprintf(sb, "LocalAddr: <nil>, ")
+	}
+	if p.AuthInfo != nil {
+		fmt.Fprintf(sb, "AuthInfo: '%s'", p.AuthInfo.AuthType())
+	} else {
+		fmt.Fprintf(sb, "AuthInfo: <nil>")
+	}
+	sb.WriteString("}")
+
+	return sb.String()
+}
+
 type peerKey struct{}
 
 // NewContext creates a new context with peer information attached.

peer/peer_test.go

@@ -0,0 +1,103 @@
+/*
+ *
+ * Copyright 2024 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package peer
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"google.golang.org/grpc/credentials"
+)
+
+// A struct that implements AuthInfo interface and implements CommonAuthInfo() method.
+type testAuthInfo struct {
+	credentials.CommonAuthInfo
+}
+
+func (ta testAuthInfo) AuthType() string {
+	return fmt.Sprintf("testAuthInfo-%d", ta.SecurityLevel)
+}
+
+type addr struct {
+	ipAddress string
+}
+
+func (addr) Network() string { return "" }
+
+func (a *addr) String() string { return a.ipAddress }
+
+func TestPeerStringer(t *testing.T) {
+	testCases := []struct {
+		name string
+		peer *Peer
+		want string
+	}{
+		{
+			name: "+Addr-LocalAddr+ValidAuth",
+			peer: &Peer{Addr: &addr{"example.com:1234"}, AuthInfo: testAuthInfo{credentials.CommonAuthInfo{SecurityLevel: credentials.PrivacyAndIntegrity}}},
+			want: "Peer{Addr: 'example.com:1234', LocalAddr: <nil>, AuthInfo: 'testAuthInfo-3'}",
+		},
+		{
+			name: "+Addr+LocalAddr+ValidAuth",
+			peer: &Peer{Addr: &addr{"example.com:1234"}, LocalAddr: &addr{"example.com:1234"}, AuthInfo: testAuthInfo{credentials.CommonAuthInfo{SecurityLevel: credentials.PrivacyAndIntegrity}}},
+			want: "Peer{Addr: 'example.com:1234', LocalAddr: 'example.com:1234', AuthInfo: 'testAuthInfo-3'}",
+		},
+		{
+			name: "+Addr-LocalAddr+emptyAuth",
+			peer: &Peer{Addr: &addr{"1.2.3.4:1234"}, AuthInfo: testAuthInfo{credentials.CommonAuthInfo{}}},
+			want: "Peer{Addr: '1.2.3.4:1234', LocalAddr: <nil>, AuthInfo: 'testAuthInfo-0'}",
+		},
+		{
+			name: "-Addr-LocalAddr+emptyAuth",
+			peer: &Peer{AuthInfo: testAuthInfo{}},
+			want: "Peer{Addr: <nil>, LocalAddr: <nil>, AuthInfo: 'testAuthInfo-0'}",
+		},
+		{
+			name: "zeroedPeer",
+			peer: &Peer{},
+			want: "Peer{Addr: <nil>, LocalAddr: <nil>, AuthInfo: <nil>}",
+		},
+		{
+			name: "nilPeer",
+			peer: nil,
+			want: "Peer<nil>",
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx := NewContext(context.Background(), tc.peer)
+			p, ok := FromContext(ctx)
+			if !ok {
+				t.Fatalf("Unable to get peer from context")
+			}
+			if p.String() != tc.want {
+				t.Fatalf("Error using peer String(): expected %q, got %q", tc.want, p.String())
+			}
+		})
+	}
+}
+
+func TestPeerStringerOnContext(t *testing.T) {
+	ctx := NewContext(context.Background(), &Peer{Addr: &addr{"1.2.3.4:1234"}, AuthInfo: testAuthInfo{credentials.CommonAuthInfo{SecurityLevel: credentials.PrivacyAndIntegrity}}})
+	want := "context.Background.WithValue(type peer.peerKey, val Peer{Addr: '1.2.3.4:1234', LocalAddr: <nil>, AuthInfo: 'testAuthInfo-3'})"
+	if got := fmt.Sprintf("%v", ctx); got != want {
+		t.Fatalf("Unexpected stringer output, got: %q; want: %q", got, want)
+	}
+}