Macro doesn't execute when defined in a project outside of analysis roots

[DanTup]

I was investigating an issue @mit-mit / @davidmorgan are seeing of macros not executing in VS Code. I can reproduce the issue and it seems to be that when the project that contains a macros definition is not in the workspace, the macro does not execute.

Here's a repro:

https://github.com/DanTup/macro-other-project-issue

This project has two projects:

• my_macro - defines a macro @WithMethod(name) that adds a method to a class
• my_macro_user - defines a class A annotated with @WithMethod('hello) to add a method called hello

If I open the entire repository in VS Code, the macro executes fine (I can hover over and jump to the definition):

However, if I open only the my_macro_user folder (so that the definition of the macro is not in the workspace), the macro doesn't execute (and no errors are shown in VS Code or in the instrumentation log):

@mit-mit was using latest Flutter master and I repro'd on Dart SDK version: 3.5.0-edge.8ef0e2a15805d3b79c64c3998fa1c9500f3654d0 (main) (Mon May 6 23:57:19 2024 +0000) on "windows_x64".

[bwilkerson]

@scheglov

[scheglov]

We discussed this internally, and the conclusion is that we don't use analysis_options.yaml of dependencies: my_macro here, to enable experiments. So, when you analyze just my_macro_user, it does not see any macros in my_macro.

There is no solution so far, at least for such random custom macro packages.
For json we could potentially use allowed_experiments.json.