fix: Our Dart crashes when it should show isolate error

[eseidel]

Something is broken in our Dart when handling a specific kind of isolate error.

Bryan accidentally discovered this with the 1.6.8 release.

If you check out 3c6d238

And try to run it with upstream dart, it shows this:

eseidel@erics-mbp shorebird % ./bin/shorebird preview        
Updating Flutter...
HEAD is now at 3d75b30b bump engine rev
Shorebird Engine • revision 9637b88761740c1ea1d6efac2e2b73235e6eb4de
Flutter 3.27.4-0.0.pre.13 • channel [user-branch] • unknown source
Framework • revision 3d75b30b18 (3 days ago) • 2025-01-28 19:25:00 -0500
Engine • revision 9637b88761
Tools • Dart 3.6.1 • DevTools 2.40.0
Building Shorebird...
Resolving dependencies... 
Downloading packages... 
Got dependencies.
✓ Fetching apps (0.2s)
Which app would you like to preview? hi_android
✓ Fetching releases (0.2s)
✓ Fetching releases (0.2s)
Which release would you like to preview? 1.0.0+1
✓ Fetching aab artifact (0.2s)
✓ Downloading release (0.2s)
Invalid argument(s): Illegal argument in isolate message: (object is a DynamicLibrary)
 <- _lib in Instance of 'UnixTerminal' (from package:mason_logger/src/ffi/unix_terminal.dart)
 <- _terminal in Instance of 'Logger' (from package:mason_logger/src/mason_logger.dart)
 <- Instance of 'ShorebirdCliCommandRunner' (from package:shorebird_cli/src/shorebird_cli_command_runner.dart)
 <- Instance of 'PreviewCommand' (from package:shorebird_cli/src/commands/preview_command.dart)
 <- field this in PreviewCommand.setChannelOnAab.<anonymous closure> (from package:shorebird_cli/src/commands/preview_command.dart)
 <- resultPort in Instance of '_RemoteRunner<Null>' (from dart:isolate)


If you aren't sure why this command failed, re-run with the --verbose flag to see more information.

You can also file an issue if you think this is a bug. Please include the following log file in your report:
/Users/eseidel/Library/Application Support/shorebird/logs/1738343928777_shorebird.log

But if you try to run with our dart: (shorebird uses our dart fork by default).

eseidel@erics-mbp shorebird % ./bin/shorebird preview        
Updating Flutter...
HEAD is now at 3d75b30b bump engine rev
Shorebird Engine • revision 9637b88761740c1ea1d6efac2e2b73235e6eb4de
Flutter 3.27.4-0.0.pre.13 • channel [user-branch] • unknown source
Framework • revision 3d75b30b18 (3 days ago) • 2025-01-28 19:25:00 -0500
Engine • revision 9637b88761
Tools • Dart 3.6.1 • DevTools 2.40.0
Building Shorebird...
Resolving dependencies... 
Downloading packages... 
Got dependencies.
✓ Fetching apps (0.2s)
Which app would you like to preview? hi_android
✓ Fetching releases (0.2s)
✓ Fetching releases (0.2s)
Which release would you like to preview? 1.0.0+1
✓ Fetching aab artifact (0.2s)
✓ Downloading release (0.2s)
../../flutter/third_party/dart/runtime/vm/object.h: 7195: error: unreachable code
zsh: abort      ./bin/shorebird preview

[eseidel]

This is the change that fixed the crash/error: 3c6d238