Built-in dart2js transformer seems to run with '--categories=all'

[DartBot]

<img src="https://avatars.githubusercontent.com/u/5757092?v=3" align="left" width="96" height="96"hspace="10"> Issue by mkustermann
Originally opened as dart-lang/sdk#21786

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This can be highly confusing for users who accidentally import 'dart:io' in a web application.

$ cat pubspec.yaml
name: foo
version: 0.1.0

$ cat web/foo.dart
import 'dart:io';
import 'dart:html';

main() {
  query('#foobar');
  stdout.writeln('hello world');
}

$ pub build
Loading source assets...
Building foo...
[Info from Dart2JS]:
Compiling foo|web/foo.dart...
[Info from Dart2JS]:
Took 0:00:05.293322 to compile foo|web/foo.dart.
Built 1 file to "build".

=> It compiles without any warning or error!

Whereas if I run dart2js manually it gives me a proper error message:
$ dart2js web/foo.dart
web/foo.dart:1:8:
Error: Library not found 'dart:io'.
import 'dart:io';
       ^^^^^^^^^
Error: Compilation failed.

I'm not sure if this is intentionally or not, but e.g. for automated scripts which run "pub build" and check for successful building of the application, this can hide errors IMHO.

We should give users warnings/errors as early as possible and never suppress them by default.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/405837?v=3" align="left" width="48" height="48"hspace="10"> Comment by zoechi

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Seems to be a dup of http://dartbug.com/21781
where 21781 is about not using --all in DartEditor by default anymore and this seems about also using -all from command line.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/5757092?v=3" align="left" width="48" height="48"hspace="10"> Comment by mkustermann

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This is orthogonal to Issue dart-lang/sdk#21781:

• Issue Editor shouldn't run "pub build --all" sdk#21781 is about what directories to build (i.e. default behavior in DartEditor when selecting "Pub Build").
• This issue is about passing the wrong flags to the $dart2js transformer (independent of directories).

[DartBot]

<img src="https://avatars.githubusercontent.com/u/46275?v=3" align="left" width="48" height="48"hspace="10"> Comment by munificent

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We can probably use a better category for stuff in web/ and bin/. The tricky part is example/, test/, benchmark/ and other user-defined directories. Any of those could contain web stuff or command-line stuff, so we have to use category all.

[matanlurey]

We are no longer supporting transformers or pub serve/build going forward (this tooling has moved elsewhere into the https://github.com/dart-lang/build repository and https://github.com/dart-lang/webdev CLI) so a fix for this is not planned.

We'll be updating the tooling section of the Dart website in the coming weeks with more formal documentation on how to get started.