Fix CopyFrom deadlock when multiple NoticeResponse received during copy

fixes #21

pgconn.go

@@ -1084,26 +1084,44 @@ func (pgConn *PgConn) CopyFrom(ctx context.Context, r io.Reader, sql string) (Co
 	}
 
 	// Send copy data
-	buf = make([]byte, 0, 65536)
-	buf = append(buf, 'd')
-	sp := len(buf)
-	var readErr error
+	abortCopyChan := make(chan struct{})
+	copyErrChan := make(chan error)
 	signalMessageChan := pgConn.signalMessage()
-	for readErr == nil && pgErr == nil {
-		var n int
-		n, readErr = r.Read(buf[5:cap(buf)])
-		if n > 0 {
-			buf = buf[0 : n+5]
-			pgio.SetInt32(buf[sp:], int32(n+4))
 
-			_, err = pgConn.conn.Write(buf)
-			if err != nil {
-				pgConn.asyncClose()
-				return nil, err
+	go func() {
+		buf := make([]byte, 0, 65536)
+		buf = append(buf, 'd')
+		sp := len(buf)
+
+		for {
+			n, readErr := r.Read(buf[5:cap(buf)])
+			if n > 0 {
+				buf = buf[0 : n+5]
+				pgio.SetInt32(buf[sp:], int32(n+4))
+
+				_, writeErr := pgConn.conn.Write(buf)
+				if writeErr != nil {
+					copyErrChan <- writeErr
+					return
+				}
+			}
+			if readErr != nil {
+				copyErrChan <- readErr
+				return
+			}
+
+			select {
+			case <-abortCopyChan:
+				return
+			default:
 			}
 		}
+	}()
 
+	var copyErr error
+	for copyErr == nil && pgErr == nil {
 		select {
+		case copyErr = <-copyErrChan:
 		case <-signalMessageChan:
 			msg, err := pgConn.receiveMessage()
 			if err != nil {
@@ -1120,13 +1138,14 @@ func (pgConn *PgConn) CopyFrom(ctx context.Context, r io.Reader, sql string) (Co
 		default:
 		}
 	}
+	close(abortCopyChan)
 
 	buf = buf[:0]
-	if readErr == io.EOF || pgErr != nil {
+	if copyErr == io.EOF || pgErr != nil {
 		copyDone := &pgproto3.CopyDone{}
 		buf = copyDone.Encode(buf)
 	} else {
-		copyFail := &pgproto3.CopyFail{Message: readErr.Error()}
+		copyFail := &pgproto3.CopyFail{Message: copyErr.Error()}
 		buf = copyFail.Encode(buf)
 	}
 	_, err = pgConn.conn.Write(buf)

pgconn_test.go

@@ -1463,6 +1463,46 @@ func TestConnCopyFromQueryNoTableError(t *testing.T) {
 	ensureConnValid(t, pgConn)
 }
 
+// https://github.com/jackc/pgconn/issues/21
+func TestConnCopyFromNoticeResponseReceivedMidStream(t *testing.T) {
+	t.Parallel()
+
+	ctx := context.Background()
+	pgConn, err := pgconn.Connect(ctx, os.Getenv("PGX_TEST_CONN_STRING"))
+	require.NoError(t, err)
+	defer closeConn(t, pgConn)
+
+	_, err = pgConn.Exec(ctx, `create temporary table sentences(
+		t text,
+		ts tsvector
+	)`).ReadAll()
+	require.NoError(t, err)
+
+	_, err = pgConn.Exec(ctx, `create function pg_temp.sentences_trigger() returns trigger as $$
+	begin
+	  new.ts := to_tsvector(new.t);
+		return new;
+	end
+	$$ language plpgsql;`).ReadAll()
+	require.NoError(t, err)
+
+	_, err = pgConn.Exec(ctx, `create trigger sentences_update before insert on sentences for each row execute procedure pg_temp.sentences_trigger();`).ReadAll()
+	require.NoError(t, err)
+
+	longString := make([]byte, 10001)
+	for i := range longString {
+		longString[i] = 'x'
+	}
+
+	buf := &bytes.Buffer{}
+	for i := 0; i < 1000; i++ {
+		buf.Write([]byte(fmt.Sprintf("%s\n", string(longString))))
+	}
+
+	_, err = pgConn.CopyFrom(ctx, buf, "COPY sentences(t) FROM STDIN WITH (FORMAT csv)")
+	require.NoError(t, err)
+}
+
 func TestConnEscapeString(t *testing.T) {
 	t.Parallel()