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.

Solution

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.

Comments

[Diwyansh]

check this stackoverflow.com/questions/58710226/….

[xerotolerant]

I found it a few minutes ago. it might be what I need.

[Diwyansh]

okay good just try it

[xerotolerant]

@Diwyansh I was successful thanks.

[Diwyansh]

Pleased to help you...

[xerotolerant]

kIsWeb is a runtime variable. The issue I'm having is at build time. I want to exclude it from the build entirely

[Ayman Barghout]

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.