Release project snapshots when their project leaves the workspace

[xperiandri]

With the transparent compiler on, the editor kept the last snapshot of every F# project it had built one for and never dropped any. Each holds the Roslyn solution it was built from, so every solution opened in a session stayed in memory until Visual Studio exited. Snapshots are now released when their project is removed and when the solution is closed.

Details

• Removal follows the workspace's change events: the project on ProjectRemoved, the old solution's projects on SolutionRemoved, SolutionCleared and SolutionReloaded. Closing the solution clears everything, next to the other caches.
• The cache counts the removals the workspace reports. A request notes the count when it starts. If the count moved by the time the request ends, or its project is no longer in the workspace, the request stores nothing and forgets that project's entries, also when the caller was cancelled. The id alone cannot tell, because a reload brings the same ids back.
• Cache sizes are unchanged.

🤖 Generated with Claude Code

[github-actions]

✅ Release notes checked

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
`vsintegration/src`	docs/release-notes/.VisualStudio/18.vNext.md

[Copilot]

🟡 Changes recommended

Late work from a reloaded solution can repopulate the cache when project IDs are preserved.

2 open findings

• Discard stale computations by solution generation, not project ID · New
• Test the removal race with gated snapshot creation · New

What changed in this PR

Releases transparent-compiler snapshots when projects leave the Visual Studio workspace, preventing old Roslyn solutions from remaining rooted.

Changes:

• Adds project and solution lifecycle cache eviction.
• Guards against late snapshot completion and adds regression tests.
• Documents the memory-leak fix in release notes.

File	Description
ProjectSnapshotCacheTests.fs	Tests snapshot eviction behavior.
FSharp.Editor.Tests.fsproj	Includes the new tests.
WorkspaceExtensions.fs	Centralizes and evicts snapshot caches.
LanguageService.fs	Hooks cache eviction into workspace and solution events.
18.vNext.md	Adds the release note.

🧠 Review effort: Balanced

[T-Gro]

🤖 🕵️ LGTM

[T-Gro]

The diff is still way too big - apply the NoBloat instructions and CodeCompaction skill.

Especially the massive code comments would benefit not just with drastic reduction, but ideally with well named functions/arguments/bindings/types making the intention clear.

If a well named piece of code just tells what the comment says - delete the comment.

• This diff adds 14 new code comment lines and 1258 new code comment chars.
• Comments bypass the type system and become stale maintenance state. Keep only durable public contracts; express implementation intent through names, functions, active patterns, discriminated unions, and types.

[T-Gro]

🤖🕵️ AI review — verify independently.

[xperiandri]

Addressed the NoBloat / CodeCompaction review in cdc7c64edd (plus a merge of main before it, no rebase):

• The change now adds 3 comment lines (one is the license header of the new test file), down from 25: a one-line doc on the cache module and a one-line doc on the test helper. The rest is carried by names: removalsSoFar, forget, removeProject, isGone and, in the tests, createProjectWithGatedText, removeFromWorkspace, reloadWorkspace, snapshotBuiltWhile, assertForgotten.
• The three tests share their setup instead of repeating it: one gated-text loader, one helper that runs a disturbance while the first request is pending, one assertion that nothing is retained and the next request builds anew.
• The two inline findings (a request begun after the removal, cancellation after publication) are fixed and answered on their threads.

The three new tests fail when the isGone check is disabled and pass with it, twice in a row. The whole FSharp.Editor.Tests run is 7206 tests with 4 failures: the two type provider F1 help tests, the type provider signature help test and fsiShouldTriggerCompletionInFsxFile. They go through the legacy incremental builder and type providers, not through the snapshot cache this PR changes.