You could use mirrors (reflection) to solve this problem. The pub package path is using reflection to access dart:io
on the standalone VM or dart:html
in the browser.
The source is located here. The good thing is, that they use @MirrorsUsed
, so only the required classes are included for the mirrors api. In my opinion the code is documented very good, it should be easy to adopt the solution for your code.
Start at the getters _io
and _html
(stating at line 72), they show that you can load a library without that they are available on your type of the VM. Loading just returns false if the library it isn't available.
/// If we're running in the server-side Dart VM, this will return a
/// [LibraryMirror] that gives access to the `dart:io` library.
///
/// If `dart:io` is not available, this returns null.
LibraryMirror get _io => currentMirrorSystem().libraries[Uri.parse('dart:io')];
// TODO(nweiz): when issue 6490 or 6943 are fixed, make this work under dart2js.
/// If we're running in Dartium, this will return a [LibraryMirror] that gives
/// access to the `dart:html` library.
///
/// If `dart:html` is not available, this returns null.
LibraryMirror get _html =>
currentMirrorSystem().libraries[Uri.parse('dart:html')];
Later you can use mirrors to invoke methods or getters. See the getter current
(starting at line 86) for an example implementation.
/// Gets the path to the current working directory.
///
/// In the browser, this means the current URL. When using dart2js, this
/// currently returns `.` due to technical constraints. In the future, it will
/// return the current URL.
String get current {
if (_io != null) {
return _io.classes[#Directory].getField(#current).reflectee.path;
} else if (_html != null) {
return _html.getField(#window).reflectee.location.href;
} else {
return '.';
}
}
As you see in the comments, this only works in the Dart VM at the moment. After issue 6490 is solved, it should work in Dart2Js, too. This may means that this solution isn't applicable for you at the moment, but would be a solution later.
The issue 6943 could also be helpful, but describes another solution that is not implemented yet.