fluff

fluff is an experimental Fortran linter and formatter built on the FortFront AST and semantic APIs.

The project is useful as a FortFront-based tool prototype, but it is not yet a Ruff-equivalent production tool. Several CLI and formatter features are still tracked as open issues.

Current Scope

Implemented or partially implemented:

• style rules F001 to F015
• performance rules P001 to P007
• correctness rule C001
• formatter built on FortFront emit_fortran
• basic LSP components
• JSON/SARIF/GitHub-style output code paths

Known limits:

• configuration support has open regressions
• formatter can still move inline comments in unsafe ways
• rule selection/ignore CLI parity with Ruff is incomplete
• stdin, quiet mode, statistics, rule listing, and show-fixes UX are tracked as open issues
• AST caching is disabled in the linter path because FortFront arena/context copies are not yet safe enough

Install

git clone git@github.com:lazy-fortran/fluff.git
cd fluff
fpm build --profile release

Basic Usage

fluff check src/
fluff format src/
fluff check --output-format json src/

Use fluff --help for the options supported by the current build.

Architecture

fluff should not parse Fortran text itself. The intended flow is:

1. read source
2. parse with FortFront tooling APIs
3. run FortFront semantic analysis
4. execute AST-based lint rules
5. format through FortFront code emission plus local cleanup passes

This keeps parser and semantic behavior aligned with FortFront and avoids regex-based language analysis.

Roadmap

See ROADMAP.md and the open issues. The short version:

1. fix formatter safety first
2. finish CLI parity needed for daily use
3. repair configuration loading
4. only then improve cache/LSP polish

Related Projects

• fortfront: parser, AST, semantic analysis, formatter emission.
• standard: target language-mode behavior for LFortran Standard and Infer.

License

MIT. See LICENSE.