3 files changed, 31 insertions, 5 deletions
diff --git a/src/encoding/json/bench_test.go b/src/encoding/json/bench_test.go
index f2592e3dbd..f92d39f0c6 100644
--- a/src/encoding/json/bench_test.go
+++ b/src/encoding/json/bench_test.go
@@ -297,6 +297,22 @@ func BenchmarkIssue10335(b *testing.B) {
 	})
 }
 
+func BenchmarkIssue34127(b *testing.B) {
+	b.ReportAllocs()
+	j := struct {
+		Bar string `json:"bar,string"`
+	}{
+		Bar: `foobar`,
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			if _, err := Marshal(&j); err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}
+
 func BenchmarkUnmapped(b *testing.B) {
 	b.ReportAllocs()
 	j := []byte(`{"s": "hello", "y": 2, "o": {"x": 0}, "a": [1, 99, {"x": 1}]}`)
diff --git a/src/encoding/json/encode.go b/src/encoding/json/encode.go
index 2e1f56f882..0758b2fc9e 100644
--- a/src/encoding/json/encode.go
+++ b/src/encoding/json/encode.go
@@ -600,11 +600,11 @@ func stringEncoder(e *encodeState, v reflect.Value, opts encOpts) {
 		return
 	}
 	if opts.quoted {
-		sb, err := Marshal(v.String())
-		if err != nil {
-			e.error(err)
-		}
-		e.string(string(sb), opts.escapeHTML)
+		b := make([]byte, 0, v.Len()+2)
+		b = append(b, '"')
+		b = append(b, []byte(v.String())...)
+		b = append(b, '"')
+		e.stringBytes(b, opts.escapeHTML)
 	} else {
 		e.string(v.String(), opts.escapeHTML)
 	}
diff --git a/src/encoding/json/stream_test.go b/src/encoding/json/stream_test.go
index e3317ddeb0..ebb4f231d1 100644
--- a/src/encoding/json/stream_test.go
+++ b/src/encoding/json/stream_test.go
@@ -118,6 +118,11 @@ func TestEncoderSetEscapeHTML(t *testing.T) {
 		Ptr    strPtrMarshaler
 	}{`"<str>"`, `"<str>"`}
 
+	// https://golang.org/issue/34154
+	stringOption := struct {
+		Bar string `json:"bar,string"`
+	}{`<html>foobar</html>`}
+
 	for _, tt := range []struct {
 		name       string
 		v          interface{}
@@ -137,6 +142,11 @@ func TestEncoderSetEscapeHTML(t *testing.T) {
 			`{"NonPtr":"\u003cstr\u003e","Ptr":"\u003cstr\u003e"}`,
 			`{"NonPtr":"<str>","Ptr":"<str>"}`,
 		},
+		{
+			"stringOption", stringOption,
+			`{"bar":"\"\u003chtml\u003efoobar\u003c/html\u003e\""}`,
+			`{"bar":"\"<html>foobar</html>\""}`,
+		},
 	} {
 		var buf bytes.Buffer
 		enc := NewEncoder(&buf)