Language Server Protocol

Native LSP support with real-time diagnostics, code completion, and intelligent navigation

Fresh has native support for the Language Server Protocol (LSP), providing powerful code intelligence features across multiple programming languages.

Core Features

Fresh’s LSP integration provides:

Real-time Diagnostics

See errors and warnings in your code as you type

Code Completion

Get intelligent code completion suggestions

Go-to-Definition

Quickly jump to the definition of a symbol

Diagnostics Panel

The diagnostics panel provides a centralized view of all errors and warnings in your code.

1. Open the Panel

   Open the diagnostics panel with Show Diagnostics Panel or Toggle Diagnostics Panel from the command palette.

2. Navigate Issues

   • Up/Down: Scroll the editor to preview each diagnostic’s location
   • Enter: Jump to the diagnostic and focus the editor
   • F8: Jump to next diagnostic without the panel
   • Shift+F8: Jump to previous diagnostic

Code Folding

When the LSP server provides foldingRange, fold indicators appear in the gutter. See Editing — Code Folding for more details.

Built-in LSP Support

Fresh includes built-in LSP configurations for many languages. Simply install the server and Fresh will use it automatically:

Language	LSP Server	Install Command
Rust	rust-analyzer	rustup component add rust-analyzer
Go	gopls	go install golang.org/x/tools/gopls@latest
TypeScript/JavaScript	typescript-language-server	npm install -g typescript-language-server typescript
Python	pylsp	pip install python-lsp-server
Java	jdtls	brew install jdtls
Zig	zls	brew install zls
LaTeX	texlab	brew install texlab
Markdown	marksman	brew install marksman
C/C++	clangd	brew install llvm

Python LSP Configuration

The default Python server is pylsp. Fresh also supports several alternative Python language servers:

pyright

Recommended for type checking with strong TypeScript-like type analysis.

{
  "lsp": {
    "python": {
      "command": "pyright-langserver",
      "args": ["--stdio"],
      "enabled": true
    }
  }
}

Install: npm install -g pyright or pip install pyright

basedpyright

Enhanced pyright fork with additional features.

{
  "lsp": {
    "python": {
      "command": "basedpyright-langserver",
      "args": ["--stdio"],
      "enabled": true
    }
  }
}

Install: pip install basedpyright or uv pip install basedpyright

pylsp with plugins

pylsp supports various plugins for enhanced functionality:

{
  "lsp": {
    "python": {
      "command": "pylsp",
      "args": [],
      "enabled": true,
      "initialization_options": {
        "pylsp": {
          "plugins": {
            "pycodestyle": { "enabled": true },
            "pylint": { "enabled": true }
          }
        }
      }
    }
  }
}

Configuring LSP for a New Language

To add LSP support for a language, configure two sections in your ~/.config/fresh/config.json:

1. Define the language

   Add the language to the languages section with file extensions:

   {
     "languages": {
       "csharp": {
         "extensions": ["cs"],
         "grammar": "c_sharp",
         "comment_prefix": "//",
         "auto_indent": true
       }
     }
   }
   
2. Configure the LSP server

   Add the language server configuration to the lsp section:

   {
     "lsp": {
       "csharp": {
         "command": "/path/to/csharp-language-server",
         "args": [],
         "enabled": true
       }
     }
   }
   

The language name (e.g., "csharp") must match in both sections. Fresh includes built-in language definitions for Rust, JavaScript, TypeScript, and Python.

Configuring Language Detection via Settings UI

You can also configure language detection using the Settings UI instead of editing config.json directly:

1. Open Settings

   Use Edit → Settings… or the command palette (Ctrl+P) and search for “Settings”

2. Navigate to Languages

   Go to the Languages section

3. Add or Edit a Language

   Click on an existing language to edit it, or add a new one

4. Configure Detection

   Set the following fields:

   • Extensions: File extensions that should use this language (e.g., cs for C#, rs for Rust)
   • Filenames: Specific filenames without extensions (e.g., Makefile, .bashrc, .zshrc)
   • Grammar: The syntax highlighting grammar to use (must match a grammar name from syntect)

Example: Adding Shell Script Detection for Dotfiles

To make Fresh recognize .bashrc, .zshrc, and similar files as shell scripts:

1. Open Settings

   Open Settings (Edit → Settings…)

2. Configure bash language

   Go to Languages → bash (or create a new bash entry)

3. Add filenames

   Add filenames: .bashrc, .zshrc, .bash_profile, .profile

4. Set grammar

   The grammar should be set to Bourne Again Shell (bash) or similar

The filenames field supports glob patterns like *.conf, *rc, or /etc/**/rc.* for matching files without standard extensions. Fresh checks filenames first, then extensions, allowing dotfiles without traditional extensions to get proper syntax highlighting.