VS Code extension for the Fortran formatter Sable

VS Code formatter extension for modern free-form Fortran (f90/f95/f2003/f2008) using the sable CLI.

Quick Start

1. Install this VS Code extension.
2. Open a free-form Fortran file.
3. Run Format Document.
4. If sable is missing, choose one of:
   • Install now to install sable-fortran from inside VS Code
   • How to install for manual instructions (Copy pip command, Run installer, or Open README)
   • Or: run pip install sable-fortran directly in your preferred environment
5. If VS Code asks for a default formatter, choose Sable Fortran Formatter.
6. When prompted, choose whether to enable format-on-save (Yes or No).
7. If you choose No, format manually with Format Document.

You can also run Sable Fortran Formatter: Install formatter (sable-fortran) from the Command Palette.

No additional extension settings are required for the default sable setup if sable is available on PATH (or if fortranFormatter.path points to it).

Optional configuration

Only add settings if you want to override defaults:

{
  "fortranFormatter.path": "sable",
  "fortranFormatter.args": ["format", "--diff", "${file}"],
  "fortranFormatter.formatFolderArgs": ["format", "${folder}"],
  "fortranFormatter.useStdin": false,
  "fortranFormatter.cwd": "${workspaceFolder}",
  "fortranFormatter.timeoutMs": 10000
}

If you want format-on-save preconfigured instead of using the prompt:

{
  "[fortran-modern]": {
    "editor.defaultFormatter": "eirik.sable-fortran-formatter",
    "editor.formatOnSave": true
  },
  "[fortran_free-form]": {
    "editor.defaultFormatter": "eirik.sable-fortran-formatter",
    "editor.formatOnSave": true
  }
}

Notes

• Format Document formats the current file.
• Format Selection is supported and formats whole selected lines.
• Sable Fortran Formatter: Format Folder is available from Command Palette and Explorer folder context menu.
• Sable Fortran Formatter: Install formatter (sable-fortran) installs sable-fortran into a selected Python environment with progress and output logging.
• Sable: Reset Sable formatter settings removes Sable-specific Fortran formatter overrides from VS Code settings.
• Only modern, free-form Fortran is supported. Fixed-format (legacy) Fortran is not supported.
• If fortranFormatter.path is set by workspace/workspace-folder settings, the extension prompts for confirmation (Allow and Remember) before running it.
• After successful install, if fortranFormatter.path is invalid but the newly selected environment has sable, the extension offers to update the setting automatically.

Supported language IDs

The formatter provider is registered for:

• fortran-modern
• FortranModern
• FortranFreeForm
• fortran_free_form
• fortran_free-form

Troubleshooting

• Formatter executable not found:
  • Use the Install now prompt action, or run Sable Fortran Formatter: Install formatter (sable-fortran).
  • For manual install: python -m pip install sable-fortran.
  • If needed, set fortranFormatter.path to the absolute sable executable path for your selected environment.
• Install command fails:
  • Open the extension output channel from the error action (Show output) to inspect pip/interpreter errors.
  • Confirm you selected the intended interpreter/environment in the installer picker.
• Timeout errors: increase fortranFormatter.timeoutMs.
• Wrong project root for include/config resolution: set fortranFormatter.cwd to ${workspaceFolder} or a specific directory.
• Empty formatting output in text mode: use diff mode (--diff) or configure your formatter invocation to print formatted source to stdout.
• No format-on-save prompt: the prompt appears only after Sable Fortran Formatter is selected as the default formatter for that Fortran language, and only if [language].editor.formatOnSave is not already true.