Dart: missing import in generated file

[mgesmundo]

Hi,

using a super simple schema with a single import, the generated file does not import the right dependency:

// file: foo.fbs
namespace myspace;

table Foo {
  version: string;
}

// file: bar.fbs
include "foo.fbs";

namespace myspace;

table Bar {
  version: Foo;
}

When I compile it using:

$ flatc --dart bar.fbs

it generate only the bar_myspace_generated.dart without the import of the foo_myspace_generated.dart file that is not generated at all.

I tried using a MacOS 12.6.1 (Apple Silicon M1 Pro) running a local compiled flatc 22.10.26 and a flatc-dart 2.0.5 version. Both does not works.

What's wrong? Thank you

[enum-class]

I think you can use --gen-all flag to generate all files

[mgesmundo]

Hi @enum-class thank you for your suggestion. It is a strange behavior. If you try the test example it works without the --gen-all flag and generate all right files with the right imports, but if you enable the --gen-all flag it generate wrong files. Below the full example (a simplified version of the example into the repo):

// monster_test.fbs

include "include_test1.fbs";

namespace MyGame;

table InParentNamespace {}

namespace MyGame.Example2;

table Monster {}  // Test having same name as below, but in different namespace.

namespace MyGame.Example;

union Any { Monster, MyGame.Example2.Monster }

union AnyUniqueAliases { M: Monster, M2: MyGame.Example2.Monster }

table Referrable {
  id:ulong(key, hash:"fnv1a_64");
}

table Monster {
  enemy:MyGame.Example.Monster;
  parent_namespace_test:InParentNamespace;
  vector_of_referrables:[Referrable];
  any_unique:AnyUniqueAliases;
}

root_type Monster;

// include_test1.fbs
include "include_test2.fbs";

table TableA {
  b:MyGame.OtherNameSpace.TableB;
}

// include_test2.fbs
namespace MyGame.OtherNameSpace;

table TableB {
  version: uint8;
}

Using:

$ flatc --dart monster_test.fbs

I get 3 files:

• monster_test_my_game_generated.dart
• monster_test_my_game.example_generated.dart
• monster_test_my_game.example2_generated.dart

with the right imports each.

Using instead:

$ flatc --dart --gen-all monster_test.fbs

I get 5 files:

• monster_test_generated.dart
• monster_test_my_game_generated.dart
• monster_test_my_game.example_generated.dart
• monster_test_my_game.example2_generated.dart
• monster_test_my_game.other_name_space_generated.dart

with wrong imports in every file (not in the first one):

// this is a wrong not required import
import './monster_test_generated.dart' as ;

I hope this is helpful to investigate. Thank you.

[enum-class]

I think the behavior of flatc --dart is like this:

• It will generate separate dart files per namespace, and include them. For instance, in monster_test.fbs run it generated 3 files each for MyGame, MyGame.Example2, MyGame.Example namespace. Also, in foo/bar run, it generates just one file, because there is just one namespace (myspace) in foo and bar files.

• By adding --gen-all flag, we force it to generate files that included. so in monster_test one we can see 2 more files one for include_test1.fbs that has TableA and one for include_test2.fbs that has TableB implementation. Also, in foo/bar example, by employing --gen-all flag, we force it to generate foo.fbs which is included.

• And, the reason for weird import import './monster_test_generated.dart' as ; is that it blindly import every file in each other. So it can not find the usage of TableA which is generated in monster_test_generated.dart in other files, so leave it blank :))

I am not good at writing, but I hope I explained the situation clearly.

I need your help @mgesmundo , Since I am not a expert dart developer, could you please help me to understand from a dart developer respective, what is the correct generate output files that should we expect ?

[mgesmundo]

Thank you for your time @enum-class. Below I try to explain the dart point of view with another example.

header.fbs

namespace myspace;

table Header {
  version: int;
}

foo.fbs

include "header.fbs";

namespace myspace;

table Foo {
  header: Header;
}

bar.fbs

include "header.fbs";

namespace myspace;

table Bar {
  header: Header;
}

As you can see both Foo and Bar schemas include the Header schema and all three files use the same namespace myspace.

When I try to compile every file using:

$ flatc --dart header.fbs
$ flatc --dart foo.fbs
$ flatc --dart bar.fbs

I see three generate files:

file header_myspace_generated.dart

// automatically generated by the FlatBuffers compiler, do not modify
// ignore_for_file: unused_import, unused_field, unused_element, unused_local_variable

library myspace;

import 'dart:typed_data' show Uint8List;
import 'package:flat_buffers/flat_buffers.dart' as fb;

class Header {
  Header._(this._bc, this._bcOffset);
  factory Header(List<int> bytes) {
    final rootRef = fb.BufferContext.fromBytes(bytes);
    ...
  }
}

foo_myspace_generated.dart

// automatically generated by the FlatBuffers compiler, do not modify
// ignore_for_file: unused_import, unused_field, unused_element, unused_local_variable

library myspace;

import 'dart:typed_data' show Uint8List;
import 'package:flat_buffers/flat_buffers.dart' as fb;
import 'header_myspace_generated.dart'; // <- this is the missing import

class Foo {
  Foo._(this._bc, this._bcOffset);
  factory Foo(List<int> bytes) {
    final rootRef = fb.BufferContext.fromBytes(bytes);
    ...
  }
}

bar_myspace_generated.dart

// automatically generated by the FlatBuffers compiler, do not modify
// ignore_for_file: unused_import, unused_field, unused_element, unused_local_variable

library myspace;

import 'dart:typed_data' show Uint8List;
import 'package:flat_buffers/flat_buffers.dart' as fb;
import 'header_myspace_generated.dart'; // <- this is the missing import

class Bar {
  Bar._(this._bc, this._bcOffset);
  factory Bar(List<int> bytes) {
    final rootRef = fb.BufferContext.fromBytes(bytes);
    ...
  }
}

The import 'header_myspace_generated.dart'; is missing in both Foo and Bar generated files.

If I use:

$ flatc --dart --gen-all foo.fbs
$ flatc --dart --gen-all bar.fbs

the two generated files do not need the Header generated file because have a duplicated declaration of the Header class inside every file, that is not optimal behavior.

I hope I have explained better. Thank you.

[mgesmundo]

Thank you @enum-class and @dbaileychess for this update. Unfortunately it still to not works as expected. Using:

$ flatc --dart header.fbs
$ flatc --dart foo.fbs
$ flatc --dart bar.fbs

both foo_myspace_generated.dart and bar_myspace_generated.dart contains the Header import:

import './header_myspace_generated.dart' as myspace;

but the generated code use Header instead of myspace.Header (like the import 'package:flat_buffers/flat_buffers.dart' as fb; does).

If I remove the alias into the import:

import './header_myspace_generated.dart';

it works but it could create ambiguous imports in case of same class names into different packages imports. I'm sorry for this bad news. Thank you for your support.

[enum-class]

The problem in foo/bar example in this issue is, it does not specified which Header in which namespace should be used. I mean It should be like this: header.fbs:

namespace myspace;

table Header {
  version: int;
}

bar.fbs

include "header.fbs";

namespace myspace;

table Bar {
 header: myspace.Header; /// =>  Not Header
}

You can check example files in project: link-1 link-2

[mgesmundo]

Hi @enum-class, even if I add the full namespace, the result is the same:

header.fbs

namespace myspace;

table Header {
  version: int;
}

bar.fbs

include "header.fbs";

namespace myspace;

table Bar {
  header: myspace.Header;
}

Into the terminal:

flatc --dart bar.fbs

bar_myspace_generated.dart

// automatically generated by the FlatBuffers compiler, do not modify
// ignore_for_file: unused_import, unused_field, unused_element, unused_local_variable

library myspace;

import 'dart:typed_data' show Uint8List;
import 'package:flat_buffers/flat_buffers.dart' as fb;

// this is right!
import './header_myspace_generated.dart' as myspace;

class Bar {
  Bar._(this._bc, this._bcOffset);
  factory Bar(List<int> bytes) {
    final rootRef = fb.BufferContext.fromBytes(bytes);
    return reader.read(rootRef, 0);
  }

  static const fb.Reader<Bar> reader = _BarReader();

  final fb.BufferContext _bc;
  final int _bcOffset;

  // this is wrong
  Header? get header => Header.reader.vTableGetNullable(_bc, _bcOffset, 4);
  // it should be:
  // myspace.Header? get header => myspace.Header.reader.vTableGetNullable(_bc, _bcOffset, 4);

  @override
  String toString() {
    return 'Bar{header: ${header}}';
  }
}

Note that using:

flatc --dart --gen-all bar.fbs

the generate file contains all the Header classes but also contains the redundant (because all classes are inside the same file):

import './header_myspace_generated.dart' as myspace;

[enum-class]

@mgesmundo the generator compare the namespace of Header and current namespace, find out both are same, so it drop namesapce (myspace). Change Header namespace to something else and try.

[mgesmundo]

Hi @enum-class thank you for your best support! Yes: using a different namespace it works even if I don't understand why this is de default behaviour for Dart. My colleague that uses Golang do not have this behaviour.

[fawdlstty]

It seems that the previous commit did not work properly on the latest Dart compiler, so I made some adjustments and now it runs normally locally.