Is it allowed to have several externalLibrary ?

[Alexandre Ardhuin]

In Linking to external libraries:

A canonical library can wire itself up with zero or more external libraries using an external library directive

I understand more as >=1 but in the definition of libraryDefinition I see:

libraryDefinition:
  scriptTag? libraryName? (externalLibrary|externalForLibrary)? importOrExport* partDirective* topLevelDefinition*
  ;

If I understand correctly that means 0 or 1 externalLibrary.

So is it allowed to have several external libraries ?

---

In the context of source gen it's likely that several external lib could be used (Eg. one for JSON, one for identity(hashcode / .==), one for toString()) Moreover those external libraries would define only some of all the external members of a class from the canonical lib.

Here is an example:

person.dart

external library 'person-json.g.dart';
external library 'person-identity.g.dart';
external library 'person-tostring.g.dart';

class Person {
  final String name;

  Person(this.name);

  external Person.fromJson(Map json);
  external Map toJson();

  external int get hashCode;
  external bool operator ==(o);
  external String toString();
}

person-json.g.dart

external library for 'person.dart';

import 'dart:convert';

class Person {
  factory Person.fromJson(Map json) => new Person(json["name"]);
  Map toJson() => {"name": name};
}

person-identity.g.dart

external library for 'person.dart';

import 'dart:convert';

class Person {
  int get hashCode => hashObjects([name]);
  bool operator ==(o) => identical(this, o) || o.runtimeType == runtimeType && o.name == name;
}

person-tostring.g.dart

external library for 'person.dart';

import 'dart:convert';

class Person {
  String toString() => "Person(name=$name)";
}

Is it a valid usage of external libraries (particularly partial patches) ?