spawnDomUri fails when resolving import urls in base64 encoded uris

[sigmundch]

spawnDomUri API fails to resolve relative and "package:" uris in code encoded into a base64 URIs.

I'd assume these URIs should be resolved in terms of the window baseUri, but it doesn't seem that way. Here is a repro example:

bug.html:
    <script type="application/dart">
    import 'dart:html';
    main() {
      var baseUri = Uri.parse(window.location.href);

      // Spawning code in other files works:
      spawnDomUri(baseUri.resolve('b.dart'), [], ''); // works
      spawnDomUri(baseUri.resolve('c.dart'), [], ''); // works

      // Code that contains absolute URIs work too:
      _spawn(baseUri.resolve("packages/a/a.dart"), 1); // works
    
      // I'd expect these two examples to work in the same way:
      _spawn("packages/a/a.dart", 2); // nothing happens?
      _spawn("package:a/a.dart", 3); // fails
    }

    _spawn(String importUrl, int i) {
      var code = 'import "$importUrl";\nmain() => print("$value [data-uri-$i]");';
      // ignore the mime-type below, see issue #0
      var encoded = 'data:text/javascript;base64,${window.btoa(code)}';
      spawnDomUri(Uri.parse(encoded), [], '');
    }
    </script>

packages/a/a.dart:
    const value = "hello world";

b.dart:
    import 'packages/a/a.dart';
    
    main() => print('$value [b]');

c.dart:
    import 'package:a/a.dart';
    
    main() => print('$value [c]');

---

I see no output on the example labeled with #­2, but a failure as follows on example #­3:

'package:a/a.dart': error: line 1 pos 1: unexpected token '<'
<script type="application/dart">
^: package:a/a.dart package:a/a.dart:1
Internal error: 'package:a/a.dart': error: line 1 pos 1: unexpected token '<'
<script type="application/dart">
^

(FYI the error line seems to match the code of bug.html)

If I set DART_PACKAGE_ROOT then the example #­3 above works.

---

Attachment:
spawnuri_bug.tgz (627 Bytes)

[sigmundch]

Marked this as blocking #18007.

[vsmenon]

I think the code is written assuming the spawned URL is the package root. I.e., it can't be a package - it's the root for anything it's loading. It seems dangerous to inherit the spawner's package root - what becomes the root for anything a.dart imports? a.dart's directory - packages/a/packages?

Also, what do you mean by "nothing happens" in the relative case (ex 2)? The script has no main, so nothing should happen.

[sigmundch]

what do you mean by "nothing happens" in the relative case (ex 2)? The script has no main, so nothing should happen.

There is a main, it's just a bit more hidden. Note that in that example the main function is generated with code in _spawn().

[jmesserly]

we're removing dart:isolate from dart4web (and spawnDomUri was not implemented by JS compilers)