LSP Integration

Fresh has native support for the Language Server Protocol (LSP), providing features like:

• 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

Open the diagnostics panel with "Show Diagnostics Panel" or "Toggle Diagnostics Panel" from the command palette. In the panel, Up/Down scrolls the editor to preview each diagnostic's location; Enter jumps to the diagnostic and focuses the editor. F8 and Shift+F8 jump to next/previous diagnostic without the panel.

Diagnostics can also be shown inline at the end of each line — see Editing — Inline Diagnostics.

Signature Help

Signature help popups render markdown with proper formatting, hanging indent, and paragraph spacing.

Code Folding

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

Built-in LSP Support

Fresh includes built-in LSP configurations for many languages. 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. Alternatives:

Using pyright (recommended for type checking):

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

Install pyright with: npm install -g pyright or pip install pyright

Using basedpyright (enhanced pyright fork):

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

Install basedpyright with: pip install basedpyright or uv pip install basedpyright

Using 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, you need to configure two sections in your ~/.config/fresh/config.json:

1. languages: Define the file extensions for the language
2. lsp: Configure the language server command

For example, to add C# support:

{
  "languages": {
    "csharp": {
      "extensions": ["cs"],
      "grammar": "c_sharp",
      "comment_prefix": "//",
      "auto_indent": true
    }
  },
  "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.

Environment Variables

Pass environment variables to LSP server binaries:

{
  "lsp": {
    "rust": {
      "command": "rust-analyzer",
      "env": { "RUST_LOG": "info" },
      "enabled": true
    }
  }
}

Language ID Overrides

Some LSP servers expect a different languageId than Fresh's internal language name. Use language_id_overrides to map them:

{
  "lsp": {
    "typescript": {
      "command": "typescript-language-server",
      "args": ["--stdio"],
      "language_id_overrides": {
        "typescriptreact": "typescriptreact",
        "javascriptreact": "javascriptreact"
      }
    }
  }
}

Rust LSP Mode Switching

Use "Switch Rust Analyzer Mode" from the command palette to toggle between Full and Reduced Memory modes for rust-analyzer.

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 (Edit → Settings...)
2. Go to Languages → bash (or create a new bash entry)
3. Add filenames: .bashrc, .zshrc, .bash_profile, .profile
4. 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.