ffmt

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

Documentation | Configuration | Changelog

Installation

pip install ffmt

Or via Cargo:

cargo install ffmt

Quick start

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

Features

• Code -- indentation, whitespace normalization, keyword casing, named ends, line wrapping, operator modernization (.eq. -> ==), double-colon enforcement, trailing semicolon removal
• Comments -- rewrapping, inline spacing (S102), !< alignment, !&/& ! cleanup, format suppression (! ffmt off/on)
• Structure -- blank line management around openers/closers/#ifdef, declaration :: alignment, declaration/use compaction
• Preprocessor -- Fypp (#:if, $:, @:), C preprocessor (#ifdef), OpenACC (!$acc), OpenMP (!$omp)
• Opt-in -- multi-statement splitting, assignment alignment, & column alignment, use-statement reformatting

Most options accept true, false, or "preserve". See the configuration reference for all options.

Configuration

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

indent-width = 4
line-length = 132
keyword-case = "lower"
modernize-operators = true
enforce-double-colon = true

[whitespace]
relational = true
multdiv = false

CI

# GitHub Actions
- uses: sbryngelson/ffmt@latest
  with:
    args: "--check src/"

# pre-commit
repos:
  - repo: https://github.com/sbryngelson/ffmt
    rev: v0.3.5
    hooks:
      - id: ffmt

Other Fortran formatters

Formatter	Language	Status	Notes
fprettify	Python	Unmaintained	Free-form only. Fypp support.
findent	C	Active	Indentation and fixed/free conversion.
Codee Formatter	Proprietary	Active	Commercial. Tree-sitter based.
LFortran fmt	Rust	In development	AST-based.
Fortitude	Rust	Active	Linter with auto-fix.

License

MIT