FSharp.Refactor for Visual Studio

Functional refactoring hints with one-click quick fixes for F# — 137 rules covering correctness, performance, and idiomatic F#, running live in the Visual Studio editor.

Squiggles mark each finding (recolorable under Fonts and Colors → FSharp.Refactor Hint), and Ctrl+. applies the fix:

• isNull x || x = "" → String.IsNullOrEmpty x
• match value with Some v -> v + 1 | None -> 0 → Option.map ... |> Option.defaultValue
• Guid() (the classic accidental-empty-guid slip) → Guid.Empty or Guid.NewGuid() — your call
• d.ContainsKey k + d[k] double lookup → one TryGetValue
• sprintf "%s %d" a b → interpolated string, format-preserving
• path.ToLower().StartsWith "file:" → path.StartsWith("file:", StringComparison.OrdinalIgnoreCase)
• a fixed lookup list probed in a loop → converted to a Set
• blocking .Result inside task { } → let!
• …and 130 more, every fix engineered to preserve behavior — the full rule table is in the project README.

The same rules run in VS Code (Ionide) via the FSharp.Refactor.Analyzers NuGet package, and in bulk from the command line with the fsharp-refactor dotnet tool, which applies fixes across a whole solution with type-checked verification of every change.

Requirements

The extension analyzes through an FsAutoComplete sidecar process. Install it once:

dotnet tool install -g fsautocomplete

Open an F# project, give the first analysis a few seconds, and the squiggles appear. Diagnostics use FR-prefixed codes; compiler errors and warnings stay with Visual Studio's own F# tooling — this extension only adds the refactoring layer.

Troubleshooting

The extension logs to %TEMP%\FSharpRefactor.Vsix.log: sidecar startup, analyzer loading, diagnostics arriving, and every applied fix. If nothing shows, that file says why.