Fix JSON encoding of *string

conn.go

@@ -798,6 +798,7 @@ func (c *Conn) sendPreparedQuery(ps *PreparedStatement, arguments ...interface{}
 			continue
 		}
 
+	encode:
 		switch arg := arguments[i].(type) {
 		case Encoder:
 			err = arg.Encode(wbuf, oid)
@@ -810,6 +811,7 @@ func (c *Conn) sendPreparedQuery(ps *PreparedStatement, arguments ...interface{}
 					continue
 				} else {
 					arguments[i] = v.Elem().Interface()
+					goto encode
 				}
 			}
 			switch oid {

values_test.go

@@ -89,6 +89,8 @@ func TestJsonAndJsonbTranscode(t *testing.T) {
 		}
 		typename := conn.PgTypes[oid].Name
 
+		testJsonString(t, conn, typename)
+		testJsonStringPointer(t, conn, typename)
 		testJsonSingleLevelStringMap(t, conn, typename)
 		testJsonNestedMap(t, conn, typename)
 		testJsonStringArray(t, conn, typename)
@@ -98,6 +100,38 @@ func TestJsonAndJsonbTranscode(t *testing.T) {
 	}
 }
 
+func testJsonString(t *testing.T, conn *pgx.Conn, typename string) {
+	input := `{"key": "value"}`
+	expectedOutput := map[string]string{"key": "value"}
+	var output map[string]string
+	err := conn.QueryRow("select $1::"+typename, input).Scan(&output)
+	if err != nil {
+		t.Errorf("%s: QueryRow Scan failed: %v", typename, err)
+		return
+	}
+
+	if !reflect.DeepEqual(expectedOutput, output) {
+		t.Errorf("%s: Did not transcode map[string]string successfully: %v is not %v", typename, expectedOutput, output)
+		return
+	}
+}
+
+func testJsonStringPointer(t *testing.T, conn *pgx.Conn, typename string) {
+	input := `{"key": "value"}`
+	expectedOutput := map[string]string{"key": "value"}
+	var output map[string]string
+	err := conn.QueryRow("select $1::"+typename, &input).Scan(&output)
+	if err != nil {
+		t.Errorf("%s: QueryRow Scan failed: %v", typename, err)
+		return
+	}
+
+	if !reflect.DeepEqual(expectedOutput, output) {
+		t.Errorf("%s: Did not transcode map[string]string successfully: %v is not %v", typename, expectedOutput, output)
+		return
+	}
+}
+
 func testJsonSingleLevelStringMap(t *testing.T, conn *pgx.Conn, typename string) {
 	input := map[string]string{"key": "value"}
 	var output map[string]string