[dart-misc] [dart-announce] dart2js changes coming up

['Siggi Cherem' via Dart Announcements]

To prepare for Dart 2.0, dart2js has been refactored to use the new Common
Front End (CFE) and is being extended to support the Dart 2.0 type system
semantics. This week we’re shipping the first half of this work.

Starting with the 2.0.0-dev.37.0 release of the SDK, dart2js uses the new
front end by default. At this stage dart2js has no semantic changes: the
Dart 2.0 strong-mode semantics are not enabled, so dart2js continues to
support the Dart 1 type system. This change, however, lets us start
supporting new syntactic features of Dart 2.0, like optional new/const.

*Changes to expect in this release:*

- Small code differences (~1% code size): You may notice some generated
code is slightly different. This is expected because the internal
representation of your program has small differences between the old and
new front-end.

- Source-map changes: With the new front-end, dart2js also is using a
new mechanism to generate source-map files. We don't expect big differences
here either, the new source maps try to encode more data for locations that
are commonly used during debugging.

- Some missing error messages: The CFE is not complete and may not
report some static errors that the old front-end did. This is temporary. If
you run the analyzer on your project already, you may never notice those
missing error messages.

- No support for dart:mirrors: This announcement
<https://groups.google.com/a/dartlang.org/forum/#!topic/announce/jh8uN5S0GE4>
has more details.

- No support for '--package-root': Instead use the '--packages' option
to specify the location of a .packages file.


*Temporary option to opt out*
If you run into any issues, please file a bug
<https://github.com/dart-lang/sdk/issues/new?title=Issue%20found%20with%20the%20new%20common%20front-end%20in%20dart2js&labels=area-dart2js>
to let us know. For a short time, the Dart 1 front end will continue to
work behind a flag (`--use-old-frontend`), but we expect to remove this
flag in a few weeks.
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[Randal L. Schwartz]

The announcement also indirectly deprecates isolates, suggesting the
webworker interface is richer. Is there already a package to use
webworkers, or are we left without any access?
--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - [phone]
<***@stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
Perl/Unix/Dart consulting, Technical writing, Comedy, etc. etc.
Still trying to think of something clever for the fourth line of this .sig

[Matan Lurey]

Hi Randal.

Nothing is available in this area yet. It wouldn't be much work to get
something working (I have a proof of concept that took ~15 minutes
<https://github.com/matanlurey/web_worker_channel>). Hopefully we can have,
at minimum, some published examples by the final Dart 2.0 release. To be
fair, isolates have never been supported in DDC, so it's not much of a
breaking change on top of what already isn't supported in Dart 2-dev today.

Thanks for your interest in Dart and Web Workers!

Post by Randal L. Schwartz
The announcement also indirectly deprecates isolates, suggesting the
webworker interface is richer. Is there already a package to use
webworkers, or are we left without any access?
--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777
0095 <(503)%20777-0095>
Perl/Unix/Dart consulting, Technical writing, Comedy, etc. etc.
Still trying to think of something clever for the fourth line of this .sig
--
For more ways to connect visit https://www.dartlang.org/community
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['Siggi Cherem' via Dart Misc]

Thanks for your question Randal.

I should have called this out more explicitly in the announcement: this
change doesn't drop support for `dart:isolates` in dart2js. We continue to
support it, and my hope is that, like Matan suggested, we can have a clear
path forward for developers like you when we finally reach the 2.0 release.

Cheers,
Siggi

Post by Matan Lurey
Hi Randal.
Nothing is available in this area yet. It wouldn't be much work to get
something working (I have a proof of concept that took ~15 minutes
<https://github.com/matanlurey/web_worker_channel>). Hopefully we can
have, at minimum, some published examples by the final Dart 2.0 release. To
be fair, isolates have never been supported in DDC, so it's not much of a
breaking change on top of what already isn't supported in Dart 2-dev today.
Thanks for your interest in Dart and Web Workers!

Post by Randal L. Schwartz
The announcement also indirectly deprecates isolates, suggesting the
webworker interface is richer. Is there already a package to use
webworkers, or are we left without any access?
--
Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777
0095 <(503)%20777-0095>
Perl/Unix/Dart consulting, Technical writing, Comedy, etc. etc.
Still trying to think of something clever for the fourth line of this .sig
--
For more ways to connect visit https://www.dartlang.org/community
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['Kevin Moore' via Dart Announcements]

2.0.0-dev.37.0 is now available.

Again, if you run into any issues, please file a bug
<https://github.com/dart-lang/sdk/issues/new?title=Issue%20found%20with%20the%20new%20common%20front-end%20in%20dart2js&labels=area-dart2js> to
let us know.

Post by 'Siggi Cherem' via Dart Announcements
To prepare for Dart 2.0, dart2js has been refactored to use the new Common
Front End (CFE) and is being extended to support the Dart 2.0 type system
semantics. This week we’re shipping the first half of this work.
Starting with the 2.0.0-dev.37.0 release of the SDK, dart2js uses the new
front end by default. At this stage dart2js has no semantic changes: the
Dart 2.0 strong-mode semantics are not enabled, so dart2js continues to
support the Dart 1 type system. This change, however, lets us start
supporting new syntactic features of Dart 2.0, like optional new/const.
*Changes to expect in this release:*
- Small code differences (~1% code size): You may notice some
generated code is slightly different. This is expected because the internal
representation of your program has small differences between the old and
new front-end.
- Source-map changes: With the new front-end, dart2js also is using a
new mechanism to generate source-map files. We don't expect big differences
here either, the new source maps try to encode more data for locations that
are commonly used during debugging.
- Some missing error messages: The CFE is not complete and may not
report some static errors that the old front-end did. This is temporary. If
you run the analyzer on your project already, you may never notice those
missing error messages.
- No support for dart:mirrors: This announcement
<https://groups.google.com/a/dartlang.org/forum/#!topic/announce/jh8uN5S0GE4>
has more details.
- No support for '--package-root': Instead use the '--packages'
option to specify the location of a .packages file.
*Temporary option to opt out*
If you run into any issues, please file a bug
<https://github.com/dart-lang/sdk/issues/new?title=Issue%20found%20with%20the%20new%20common%20front-end%20in%20dart2js&labels=area-dart2js>
to let us know. For a short time, the Dart 1 front end will continue to
work behind a flag (`--use-old-frontend`), but we expect to remove this
flag in a few weeks.

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