[[http://melpa.org/#/fsharp-mode][file:http://melpa.org/packages/fsharp-mode-badge.svg]] [[https://stable.melpa.org/#/fsharp-mode][file:https://stable.melpa.org/packages/fsharp-mode-badge.svg]] [[https://github.com/fsharp/emacs-fsharp-mode/actions][file:https://github.com/fsharp/emacs-fsharp-mode/workflows/CI/badge.svg]]
Provides support for the F# language in Emacs. Includes the following features:
** LSP mode
The current version of =fsharp-mode= installs =fsautocomplete.exe= automatically via =eglot-fsharp.el= (part of this mono repo, [[https://melpa.org/#/eglot-fsharp][eglot-fsharp on melpa]]) or [[https://github.com/emacs-lsp/lsp-mode][lsp-mode]] (untested).
=fsharp-mode= is tested with Emacs 27.1+ and NET Core 6 (LTS)
** Installation
*** Package
=fsharp-mode= is available on [[https://melpa.org][MELPA]] and can be installed using the built-in package manager.
If you're not already using MELPA, add the following to your init.el:
;;; Initialize MELPA (require 'package) (add-to-list 'package-archives '("melpa" . "http://melpa.org/packages/")) (unless package-archive-contents (package-refresh-contents)) (package-initialize)
;;; Install fsharp-mode (unless (package-installed-p 'fsharp-mode) (package-install 'fsharp-mode))
(require 'fsharp-mode)
If you are a user of [[https://github.com/jwiegley/use-package][use-package]] you can instead do
(use-package fsharp-mode :defer t :ensure t)
*** From source
I recommend to use [[https://cask.github.io/why-cask.html][Cask]]. Add this to your =Cask= file:
(depends-on "fsharp-mode" :git "https://github.com/fsharp/emacs-fsharp-mode.git")
** Eglot integration
The =eglot-fsharp= integration is not part of [[https://melpa.org/#/fsharp-mode][fsharp-mode on melpa]].
It is available via the seperate package [[https://melpa.org/#/eglot-fsharp][eglot-fsharp on melpa]].
Add to your config:
(require 'eglot-fsharp)
and execute =M-x eglot=
With eglot running use xref-find-definitions (bound to =M-.= pr. default) to go to definition. Completions are accessable via. completion-at-point (or a completion backend ex. company-mode [[https://melpa.org/#/company]])
** Projects
=fsharp-mode= has support for Emacs build-in project management via =project.el=
** Configuration
*** Compiler and REPL paths
The F# compiler and interpreter should be set to good defaults for your OS as long as the relevant executables can be found on your PATH or in other standard locations. If you have a non-standard setup you may need to configure these paths manually.
On Windows:
(setq inferior-fsharp-program "c:\Path\To\Fsi.exe")
On Unix-like systems, you must use the --readline- flag to ensure F# Interactive will work correctly with Emacs. Typically =fsi= and =fsc= are invoked through the shell scripts =fsharpi= and =fsharpc=:
(setq inferior-fsharp-program "path/to/fsharpi --readline-")
*** Key Bindings
If you are new to Emacs, you might want to use the menu (call =menu-bar-mode= if you don't see it). However, it's usually faster to learn a few useful bindings:
| Key binding | Description |
|------------------+-------------------------------------------|
| =C-c C-r= | Evaluate region |
| =C-c C-f= | Load current buffer into toplevel |
| =C-c C-e= | Evaluate current toplevel phrase |
| =C-M-x= | Evaluate current toplevel phrase |
| =C-M-h= | Mark current toplevel phrase |
| =C-c C-s= | Show interactive buffer |
| =C-c C-c= | Compile with fsc |
| =C-c x= | Run the executable |
| =C-c C-a= | Open alternate file (.fsi or .fs) |
| =C-c l= | Shift region to left |
| =C-c r= | Shift region to right |
| =C-c
To interrupt the interactive mode, use =C-c C-c=. This is useful if your code does an infinite loop or a very long computation.
If you want to shift the region by 2 spaces, use: =M-2 C-c r=
In the interactive buffer, use ==M-RET= to send the code without explicitly adding the =;;= thing.
** Editor
In order to change tab size it is possible to put this in emacs profile:
(setq-default fsharp-indent-offset 2)
Because the F# language is sensitive to indentation, you might wan't to highlight indentation:
(add-hook 'fsharp-mode-hook 'highlight-indentation-mode)
** Troubleshooting
=fsharp-mode= is still under development, so you may encounter some issues. Please report them so we can improve things! Open an issue on [[https://github.com/fsharp/emacs-fsharp-mode/][Github]].
*** No autocompletion in FSX files
The root cause is documented in this Ionide issue: [[https://github.com/ionide/ionide-vscode-fsharp/issues/1244][4.2.0 - No auto complete or typechecking in FSX files]]
As a workaround can add a reference to the facade netstandard assembly (path is platform/SDK-dependent).
On Arch Linux using [[https://aur.archlinux.org/packages/dotnet-sdk-lts-bin][dotnet sdk lts]] add this to your =fsx= file:
*** Project file issues
If your project file does not seem to be being parsed correctly, so that you have missing references or other incorrect intellisense results, it is possible to obtain a detailed log of LSP events in this buffers:
** Contributing
This project is maintained by the [[http://fsharp.org/][F# Software Foundation]], with the repository hosted on [[https://github.com/fsharp/emacs-fsharp-mode][GitHub]].
Pull requests are welcome. Please run the test-suite with Eldev =eldev -dtT test= before submitting a pull request.
*** Maintainers
The maintainers of this repository appointed by the F# Core Engineering Group are:
Previous maintainers: