clean up macro examples and README.md, remove run.dart script

[jakemac53]

• Delete run.dart script and update the README.md to indicate you can just pass --enable-experiment=macros.
• Break up user_main.dart into separate scripts for each macro example, which allows you to run the ones that do work, and also keeps the example apps more targetted. These were only combined into one previously to make it easier to run them through run.dart.
• Update the observable example so it is runnable.
• Update the data class example to create the unnamed constructor instead of one called gen.

[mnordine]

I checked out this branch, and did:

$ dart --version
Dart SDK version: 3.4.0-34.0.dev (dev) (Mon Jan 15 16:04:21 2024 -0800) on "macos_arm64"

$ dart pub get
$ dart --enable-experiment=macros run bin/json_serializable_main.dart  
                                                         
Error: Exception when reading 'org-dartlang-macro:///a/b/c/.dart_tool/package_config.json': FileSystemException(uri=org-dartlang-macro:///a/b/c/.dart_tool/package_config.json; message=StandardFileSystem only supports file:* and data:* URIs)
Crash when compiling org-dartlang-macro:///a/b/c/main.dart:
Invalid argument(s): Exception when reading 'org-dartlang-macro:///a/b/c/.dart_tool/package_config.json': FileSystemException(uri=org-dartlang-macro:///a/b/c/.dart_tool/package_config.json; message=StandardFileSystem only supports file:* and data:* URIs)

#0      ProcessedOptions._findPackages.checkInDir (package:front_end/src/base/processed_options.dart:671:9)
<asynchronous suspension>
#1      ProcessedOptions._findPackages (package:front_end/src/base/processed_options.dart:676:22)
<asynchronous suspension>
#2      ProcessedOptions._getPackages (package:front_end/src/base/processed_options.dart:556:24)
<asynchronous suspension>
#3      ProcessedOptions.getUriTranslator (package:front_end/src/base/processed_options.dart:481:32)
<asynchronous suspension>
#4      generateKernelInternal.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:73:37)
<asynchronous suspension>
#5      withCrashReporting (package:front_end/src/fasta/crash.dart:133:12)
<asynchronous suspension>
#6      kernelForProgramInternal.<anonymous closure> (package:front_end/src/api_prototype/kernel_generator.dart:62:29)
<asynchronous suspension>
#7      CompilerContext.clear (package:front_end/src/fasta/compiler_context.dart:139:3)
<asynchronous suspension>
#8      kernelForProgramInternal (package:front_end/src/api_prototype/kernel_generator.dart:61:10)
<asynchronous suspension>
#9      _compileMacros (package:front_end/src/kernel_generator_impl.dart:349:7)
<asynchronous suspension>
#10     precompileMacros (package:front_end/src/kernel_generator_impl.dart:305:16)
<asynchronous suspension>
#11     generateKernelInternal.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:104:11)
<asynchronous suspension>
#12     withCrashReporting (package:front_end/src/fasta/crash.dart:133:12)
<asynchronous suspension>
#13     generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:49:12)
<asynchronous suspension>
#14     CompilerContext.clear (package:front_end/src/fasta/compiler_context.dart:139:3)
<asynchronous suspension>
#15     generateKernel (package:front_end/src/kernel_generator_impl.dart:48:10)
<asynchronous suspension>
#16     kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#17     SingleShotCompilerWrapper.compileInternal (file:///Volumes/Work/s/w/ir/x/w/sdk/pkg/vm/bin/kernel_service.dart:419:11)
<asynchronous suspension>
#18     Compiler.compile.<anonymous closure> (file:///Volumes/Work/s/w/ir/x/w/sdk/pkg/vm/bin/kernel_service.dart:225:45)
<asynchronous suspension>
#19     _processLoadRequest (file:///Volumes/Work/s/w/ir/x/w/sdk/pkg/vm/bin/kernel_service.dart:906:37)
<asynchronous suspension>

Similar result for all examples.

[jakemac53]

@mnordine did you run a dart pub get?

[jakemac53]

Also fwiw, the observable one is I think the only one that works right this moment

[mnordine]

@mnordine did you run a dart pub get?

Yes, multiple times.

Also fwiw, the observable one is I think the only one that works right this moment

Ok, there is no file in bin for that one.

[davidmorgan]

@mnordine that issue was fixed very on Jan 19th--you'll need a more recent SDK.

[jakemac53]

Ok, there is no file in bin for that one.

Oh sorry, I meant the auto_dispose one, in this PR. I have another PR out which adds a main for observable which does in fact work as well.

[mnordine]

@mnordine that issue was fixed very on Jan 19th--you'll need a more recent SDK.

Ok, I'll prob wait until next dev release, since latest on brew was built on Jan 18. Thanks.