Meta Issue - Tracks all issues needed to deploy Dart 2.0

[sigmundch]

This is a meta-issue to track in one place all pending tasks to ship the shared FE to all of our tools

Analyzer integration

• resynthesize element model from kernel

  • convertion of kernel to EM (in progress: 73% 396/536 tests passing)
  • modify kernel to include @informational data
  • kernel-team: random-access support in kernel

• implement type checker in FE

• copy FE type-inference results to analyzer ast

• complete fasta-parser for analyzer

  • handle mismatch in low-level error recovery
  • all of analyzer parser error messages handled in FE
  • full unit test coverage: analyzer, analysis server, code completion, dartfmt, source_gen, angular

Error recovery revisited

• design error recovery for analysis purposes
  • Includes Fasta generates Kernel that does not correspond to the original code AST #30267, Parsing of a unit with errors throws #30266
• decisions to make: approach on compile-with-errors and reporting compile-time errors at runtime

FE features for Dart2js integration

• adding platform.dill to the SDK
• support for dart:_internal in native unit tests
• support for deferred loading (implement deferred loading in fasta #30273)
• allow external-const-factory for fromEnvironment (remove warning about patch not found for external-const-factory #30157)
• make unnamed mixin sharing optional

FE features for bazel integration

• tree shaking implementation make modular kernel tree-shaker agnostic transformers #29954

Kernel Support

• inject strong mode type checks in kernel (Kernel generated by FE should have strong-mode type checks #30270)
• Kernel mode should retain the existing support we have for Dart API (Kernel mode should retain the existing support we have for Dart API #29989)
• Support for starting up from a core snapshot when using kernel files (Support for core snapshots in the Dart binary when using kernel so we do not go through the corelib bootstrapping process on startup #28056)
• Transform the kernel file directly into Dart VM heap objects when reading the kernel file (Transform the kernel file directly into Dart VM heap objects when reading the kernel file #28057)

Dart VM and Flutter Engine/tools

• support for using outline.dill in incremental generator (Accept platform.dill in incremental kernel generator #29835)
• add outline.dill to the SDK
• Implement semantic support for generic functions (Implement semantic support for generic functions (was Generic function type arguments should be reified) #28517)
• add kernel_service.dill and vmservice.dill to the SDK
• issues with externals in .dill and with trimmed binaries (Support compiling vmservice with an external outline of the sdk #30111)
• hot reload issues (support hot reload from a partial kernel file #30109, Loading of incremental kernel files results in broken VM types #30322)
• incremental generator can rebuild hot-reload delta when VM reload didn't succeed (support failed reloads/rebuilding deltas in incremental generator #30377)
• Add support for dart front end when building and deploying apps using flutter tools (Add support in flutter tools to use the new dart front end while loading flutter apps to the device #28050)
• Migrate the hot reload logic to use the incremental compilation model in dart front end (Add support in flutter tools for incremental compilation of sources using the new Dart Front End #28051)
• Ensure all source level debugging works without any regressions when in kernel mode (Ensure all source level debugging works without regressions when in kernel mode #28063)
• Add support to enable bootstrapping of the Dart Front End in the Dart build (Add support in the dart VM build process to enable boot strapping of the Dart Front End #30374)
• Strong mode clean patch files for VM (Strong mode clean patch files for VM #31052)
• Handle strong mode annotations in the VM (Perform covariant generic checks in the VM for strong mode compliance #31312)

FE Completeness

• local type variables
• other corner cases: Parsing of a unit with errors throws #30266, No type arguments in RedirectingFactoryBody #30258, Fasta doesn't support annotations on typedefs #30034, Fasta parser doesn't support annotations on local functions #30031, Improve error messages #30196, Fasta doesn't support annotations on directives #30284
• partial support for conditional imports: CFE should use environment to resolve conditional imports and check against interface files #30143
• revisit existing test discrepancies

Speed

• create benchmark for incremental kernel generator and hot reload
• Performance of hot reloading a flutter app with the new front-end is acceptable (Performance of hot reloading a flutter app with the new front-end is acceptable #28090)
• Performance of initial load and startup of a flutter app with the new front-end (Performance of initial load and startup of a flutter app with the new front-end #28089)
• Performance of command line dart with new front-end running dart programs is acceptable (Performance of command line dart with new front-end running dart programs is acceptable #28088)

Memory footprint

• Kernel front-end increases memory footprint by over 5x (Kernel front-end increases memory footprint by over 5x #28585)

Maturity & Cleanup

• support for libraries.json provide a way to specify libraries.json to fasta on the command line #29882
• support for patching
• uniform error handling use messages.yaml for all FE messages #30080
• prevent missing context in unit tests ensure we don't have a missing context in unit tests #30269
• track outer package dependencies check outer package dependencies in subpackage_dependencies_test #30271
• provide better error messages for bad options in public API (improve error message for missing scheme #30254, validate that the same input is not given as summary and linkedDependency #30256)
• make FE strong clean make frontend strong clean #28673

[zanderso]

Zach, I have moved this comment over to the top block to have everything in one place.

[bwilkerson]

Re: full unit test coverage for the parser. Should we also be testing packages such as 'source_gen' that are heavily dependent on analyzer?

The list above explicitly mentions parser errors and type checking. Do we have a clear road map for generating other errors in FE? Do we have a plan for how we're going to handle discrepancies between the errors produced by FE and those produced by analyzer? (This impacts quick fixes and the "// ignore" feature.

[sigmundch]

Re: full unit test coverage for the parser. Should we also be testing packages such as 'source_gen' that are heavily dependent on analyzer?

yes, added them to the list as well

Do we have a clear road map for generating other errors in FE? Do we have a plan for how we're going to handle discrepancies between the errors produced by FE and those produced by analyzer? (This impacts quick fixes and the "// ignore" feature.

I'll start a thread offline about this.

[a-siva]

I am setting the milestone of this bug as 2.0-Beta1 which is more reasonable as we want all the above to be done before declaring beta complete.

[chalin]

Which subitem can I use to track the added support of runtime checks to dart2js and the VM? I see no item for "implement runtime checks" (for strong mode features). I'd like to use such an issue in the Strong mode docs.

cc @kwalrath

[a-siva]

issue #31312 was used to track support for runtime checks in the VM

[chalin]

@a-siva - thanks. The issue is closed, so will VM support be available in the next dev release (2-dev.27)?

[a-siva]

We are consolidating all the Dart 2 features under the --preview-dart-2 flag and this consolidation should happen by the next dev release (2-dev-24).
In 2-dev-23 you should be able to pass the flags
--preview_dart_2 --strong --reify-generic-functions
to get the strong mode runtime checks.

[chalin]

Thanks, --preview_dart_2 --strong --reify-generic-functions seems to be doing the trick.

[chalin]

@a-siva - when will --strong and --reify-generic-functions be placed "under" --preview-dart-2 (so that we need only use one option)? And is there an issue I can follow to track that?

[a-siva]

We are one CL away from @sivachandra to get to that point, I have created #32296 to track this

[dgrove]

We're now tracking issues needed for Dart2 Stable in the Dart2-Beta 3/Beta4/Stable milestones. Closing this meta-issue.