ditto

Its transformation ability is perfect. However, if it is made to laugh, it can't maintain its disguise.

A portable library which provides type-safe form generation and validation.

This core library is intended to be used in conjunction with other libraries such as scotty-form and ditto-lucid.

Requirements

Tested on GHC 9.6 through 9.14. GHC 9.10+ uses GHC2024 by default; older supported GHC versions fall back to GHC2021 or Haskell2010 with the required extensions enabled in the cabal file.

Cabal

Use this for day-to-day development (fast incremental rebuilds):

cabal test --enable-tests

Nix (flake)

Pinned nixpkgs and package checks:

nix build
nix flake check
nix develop

• nix flake check — build library and run the test suite in an isolated Nix derivation (CI uses this).
• nix develop — enter a shell with GHC, cabal-install, and HLS; run cabal test for iterative work.
• Flake source includes all project files under the repo root (not only git-tracked paths). flake.lock pins nixpkgs.

0.5.0 upgrade notes

• Recommended toolchain: GHC 9.10+ for GHC2024.
• Dependency bounds are intentionally permissive (base >= 4.14); older GHC releases remain supported where possible.
• inputFile: Default environment is an empty upload (no error on initial render); Missing on submit still errors.
• hoistForm is exported from Ditto.Core.