ffmt 0.2.0

# ffmt

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A fast, configurable Fortran formatter with support for Fypp, Doxygen, and OpenACC/OpenMP directives. Written in Rust. Installable via `pip`.

## Installation

```bash
pip install ffmt
```

Or via Cargo:

```bash
cargo install ffmt
```

## Usage

```bash
ffmt src/                        # format in-place
ffmt --check src/                # CI mode (exit 1 if changes needed)
ffmt --diff src/                 # show colored diff
ffmt -j 8 src/                   # parallel
cat file.fpp | ffmt -            # stdin/stdout
ffmt --range 10:50 file.fpp      # format only lines 10-50
```

## What it does

- **Indentation** -- scope-based indentation for all Fortran constructs
- **Whitespace** -- consistent spacing around operators, commas, colons, parentheses
- **Keywords** -- case normalization (`IF` -> `if`, `ENDDO` -> `end do`)
- **Continuation lines** -- normalized with proportional re-indentation
- **Preprocessor** -- Fypp (`#:if`, `#:for`), OpenACC (`!$acc`), OpenMP (`!$omp`) handled correctly

### Configuration

Create `ffmt.toml` or add `[tool.ffmt]` to `pyproject.toml`:

```toml
indent-width = 4
line-length = 132
keyword-case = "lower"         # lower, upper, preserve
normalize-keywords = true      # enddo -> end do
named-ends = true              # end subroutine -> end subroutine s_foo
align-declarations = true      # align :: in consecutive declarations
unicode-to-ascii = true        # Greek/math symbols -> LaTeX in comments
rewrap-comments = true         # wrap long comments at line-length
rewrap-code = true             # wrap long code lines at line-length
space-after-comment = true     # !comment -> ! comment
collapse-double-spaces = true  # x  =  y -> x = y
keyword-paren-space = true     # if( -> if (
fypp-list-commas = true        # normalize commas in Fypp '[...]' args

[whitespace]
relational = true              # ==, /=, <, <=, >, >=
logical = true                 # .and., .or., .not.
plusminus = true                # binary +, -
multdiv = false                 # *, /
power = false                   # **
assignment = true               # =
declaration = true              # ::
comma = true                    # space after comma
```

All options have sensible defaults -- most projects need no config file at all.

### Preserved as-is

- String literals and inline expressions (`${...}$`, `@{...}@`)
- Comment contents and Doxygen alignment (`!<`, `!>`, `!!`)
- Continuation line structure
- `#ifdef`/`#endif` blocks (no indentation change)

## Editor integration

ffmt includes a built-in LSP server for real-time format-on-save:

```bash
ffmt --lsp
```

### VS Code

```json
{
    "fortran.formatting.formatter": "ffmt",
    "fortran.formatting.args": ["--stdin-filepath", "${file}", "-"]
}
```

### Vim/Neovim

```vim
autocmd BufWritePost *.fpp,*.f90 silent !ffmt %
" Or: set formatprg=ffmt\ -
```

### Neovim (LSP)

```lua
vim.lsp.start({
    name = "ffmt",
    cmd = { "ffmt", "--lsp" },
    root_dir = vim.fs.dirname(vim.fs.find({ "ffmt.toml", "pyproject.toml" }, { upward = true })[1]),
})
```

## CI integration

### GitHub Actions

```yaml
- uses: sbryngelson/ffmt@v0.1.0
  with:
    args: "--check src/"
```

### pre-commit

```yaml
repos:
  - repo: https://github.com/sbryngelson/ffmt
    rev: v0.1.0
    hooks:
      - id: ffmt
```

## Other Fortran Formatters

| Formatter | Language | Status | Notes |
|-----------|----------|--------|-------|
| [fprettify](https://github.com/fortran-lang/fprettify) | Python | Unmaintained (last release 2020) | Free-form only. Fypp support. Requires multiple passes for convergence. |
| [findent](https://github.com/wvermin/findent) | C | Active | Indentation and fixed/free conversion. No whitespace normalization. |
| [Codee Formatter](https://www.codee.com) | Proprietary | Active | Commercial. Tree-sitter based. Fixed and free-form. |
| [LFortran fmt](https://lfortran.org) | Rust | In development | AST-based. Part of the LFortran compiler project. |
| [Fortitude](https://github.com/PlasmaFAIR/fortitude) | Rust | Active | Linter with auto-fix, not a full formatter. Tree-sitter based. |
| [f90-mode](https://www.gnu.org/software/emacs/manual/html_node/emacs/Fortran.html) | Emacs Lisp | Active | Emacs built-in. Indentation only. |

## License

MIT