Ignore lines starting with #: (RFC-1337)

[Martin521]

Description

Implements RFC-1337

Checklist

• Test cases added
• Release notes entry updated:

[github-actions]

❗ Release notes required

You can open this PR in browser to add release notes: open in github.dev

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
`src/Compiler`	docs/release-notes/.FSharp.Compiler.Service/11.0.100.md

[github-actions]

🔍 Tooling Safety Check — Affects-Bootstrap
Affects-Bootstrap: modifies lex.fsl (lexer processed by FsLex during bootstrap)

Generated by PR Tooling Safety Check · opus46 4.1M · ◷

[T-Gro]

What else would be needed for lightweight tooling accessibility?
A dedicated package for quick lexing of F# code and returning content of the ignored lines ?

( Initial experiments can use hand rolled text search, but to fully cover the language grammar a dedicated scanner for those ignored directives would be more robust)

[Martin521]

@T-Gro

I am not sure what exactly you are after.

For "dotnet run"-like behavior, you need to

1. parse the directives
2. create a temporary / hidden project file
3. track the (implicit and explicit) dependencies (for cache invalidation)
4. programmatically call msbuild for the "virtual project file"
5. deal with options, file i/o, caching, errors, cleanup, orchestration

These steps / layers are all dealt with in the runfs prototype, nicely separated into different source files.
Tricky are steps 2 - 4, because they contain details and workarounds that depend on the sdk version (especially msbuild and msbuild targets). That's why I call runfs a prototype. For quality tooling, it would have to be part of the sdk.

But for experimentation, the runfs code base should be a good starting point.

However, I might still misunderstand your goals.