metadata: remove String method (#7374)

metadata/metadata.go

@@ -90,21 +90,6 @@ 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

@@ -22,7 +22,6 @@ import (
 	"context"
 	"reflect"
 	"strconv"
-	"strings"
 	"testing"
 	"time"
 
@@ -339,26 +338,6 @@ 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.