How to ignore package when building flutter project for web?

Question

I have a project which uses flutter_libserialport library on macOS. I am modifying it to work on web however this library does not work on web.

I am building a web implementation using navigator.serial in javascript which works fine.

However when I attempt to build the project for web I get the following error

/opt/homebrew/Caskroom/flutter/2.2.3/flutter/.pub-cache/hosted/pub.dartlang.org/libserialport-0.2.0+3/lib/src/config.dart:25:8: Error: Not found: 'dart:ffi'
import 'dart:ffi' as ffi;

This makes sense since FFI is not available on web.

But I don't even need the libserialport library on web any way.

How can I get flutter to ignore it?

I tried this however it doesn't contain information on how to exclude a package.

It also does not contain information on how to ignore it specifically for web. It seems to just ignore it in general.

check this https://stackoverflow.com/questions/58710226/how-to-import-platform-specific-dependency-in-flutter-dart-combine-web-with-an. — Diwyansh, Jan 03 '22 at 12:50

Ayman Barghout · Answer 1 · 2022-01-03T13:04:34.213

Maybe you should guard your usages of libserialport with the kIsWeb predicate like following:

if(!kIsWeb){
// libserialport code execution here
}

I searched a lot as well and didn't find a way you can do that, I think this should be handled by the package itself not the package's users like in path_provider for instance.

As a workaround I have created a dummy libserialport's SerialPort class for web only as follows:

dummy_serialport.dart:

class SerialPort {
  final String name;
  static List<String> availablePorts = ['dummy'];
  static SerialPortError? lastError;
  SerialPort(this.name);

  bool openReadWrite() {
    return false;
  }
}

class SerialPortError {}

// add more properties and functions as needed

main.dart:


import 'package:libserialport/libserialport.dart'
    if (dart.library.html) './dummy_serialport.dart'
    if (dart.library.io) 'package:libserialport/libserialport.dart';

....
 if (!kIsWeb) {
      final name = SerialPort.availablePorts.first;
      final port = SerialPort(name);
      if (!port.openReadWrite()) {
        print(SerialPort.lastError);
        exit(-1);
      }
    }
    ....
....

It's bad, I know :( but it works! maybe you can contact the package author to get more insight and if opening a PR where the interfaces are separated from the FFI implementation so that importing the classes wouldn't break web or something.

kIsWeb is a runtime variable. The issue I'm having is at build time. I want to exclude it from the build entirely — xerotolerant, Jan 03 '22 at 12:23
Yea, you are right. It's really weird that when I searched I found nothing but I came up with a really bad workaround I hope it helps, for now, I'll update my answer. — Ayman Barghout, Jan 03 '22 at 12:53

How to ignore package when building flutter project for web?

1 Answers1