VSCode-FPP

VSCode extension for FPP Language Support.

FPP is a modeling language for the F Prime flight software framework.

Get Started

The extension needs the fpp_lsp_server executable and a valid F´ build cache.

Language server

Install the language server into your project's Python virtual environment:

pip install fprime-fpp-lsp

When you open a .fpp file, the extension locates fpp_lsp_server automatically:

1. the fpp.serverPath setting, if you set it explicitly;
2. the workspace Python venv — discovered via the Python extension or by scanning for a .venv/venv/env directory (override with fpp.pythonVenv);
3. fpp_lsp_server on your PATH.

If a venv is found but fprime-fpp-lsp is not installed, the extension offers to run pip install fprime-fpp-lsp for you and then starts the server.

The FPP Language Server status item (in the language status menu, next to the FPP Project item) shows which binary was detected, its version, and where it came from. Click Change (or run FPP: Select Language Server) to browse for a specific executable or return to auto-discovery.

For venv installs, the extension periodically checks PyPI for a newer fprime-fpp-lsp and offers to update it in place. Disable this with fpp.checkForUpdates, or trigger it manually with FPP: Check for Language Server Update.

Build cache

1. Run fprime-util generate
2. Open a .fpp file. The project should start indexing and references should resolve.

Troubleshooting

When first loading up your F Prime project, you may notice errors. This is because the compiler doesn't know where to search for FPP declarations.

The language server reads project configuration from a .fpp-lsp file at the workspace root (see docs/fpp-lsp-config.md). It tells the server which locs.fpp to index — this file is generated during build time in the cmake build folder, e.g. build-fprime-automatic-native/locs.fpp. If you do not have a build-fprime-automatic-native/ folder, run fprime-util generate.

You can create/update .fpp-lsp from the editor: run FPP: Select Locs file inside workspace (fpp.select) and pick the discovered locs.fpp (or choose to scan the whole workspace). The extension writes your choice into .fpp-lsp and the server re-indexes automatically. You can also edit .fpp-lsp by hand — the server picks up changes on save.

An example .fpp-lsp:

# Point the server at the locs file inside your F´ build cache.
buildCache: build-fprime-automatic-native

It's recommended to 'pin' the FPP project status item so it's easy to reload/reindex the project.

Features

• Syntax highlighting
• Code completion
  • Syntax level completion
  • Semantic specific identifier lookup
    • When searching for a type, only types will be shown. Same goes for ports, components etc.
• Syntax Signature Display
  • This should pop up while you are typing but can be manually triggered, see VSCode Docs
  • Includes descriptions on what each field does
• Hover information
  • Shows what references resolved to
• Go-to Reference (Ctrl-Click)
• Document Links
  • Used when referencing a file directly in FPP (for example the instance at specifier).

Technical Description

This VSCode extension is essentially a FPP compiler frontend written in TypeScript using ANTLR4. It injests a 'locs' file generated during the FPrime build process which will tell the compiler which files to include during its variable/type declaration stage.

Files are parsed and reduced in a separate worker thread and then sent through the compilers declaration collection in the main thread.

Development instructions

To set up dependencies you will need NodeJS and a package manager like npm or yarn:

$ yarn install

When making a change to the ANTLR definition (src/grammar/Fpp.g4), you will need to regenerate the generated files.

$ yarn antlr

To build the extension into bundled JavaScript:

$ yarn build

Once the extension is built, there should be an out/ directory at the project root. You can then test the extension by clicking "Run and Debug" and then clicking the run button on "Run Extension" to launch an development VSCode environment.

To package the extension into a VSIX file you can use:

$ yarn package

This will generate a .vsix file, from which an extension can be installed in VSCode following instructions: Install from a VSIX

To clean the build artifacts, you can use:

$ yarn clean