A Haskell implementation of JSON Schema (Draft 4).

Hackage / GitHub / Travis CI

Notes

• As of 2017 json-schema-org has begun releasing new drafts of the standard. Once this work stabilizes hjsonschema will add coverage for the latest draft.

• Requires pcre (pkgs.pcre in Nixpkgs).

• Schemas with circular references can cause infinite loops. hjsonschema does loop detection but it may not be solid yet -- please open an issue if you find a situation where it fails.

Example

See here.

Tests

Run all tests:

stack test

Run only local tests:

stack test hjsonschema:local

Run remote tests (makes GETs to json-schema.org, also temporarily starts an HTTP server on port 1234):

stack test hjsonschema:remote

Details

Goals

• Be a correct and fast implementation of the spec.

• Be a useful reference for implementers in other languages. Haskell's high level nature, expressive type system and referential transparency suit this purpose well.

Issues

• Doesn't pass all of the tests in the language agnostic test suite. See the issue list for details.

• Uses the pcre-heavy regular expression library for the "pattern" validator. It should use a library based on the ECMA 262 regex dialect, which the spec requires.

• Currently doesn't support the optional "format" validators.

Vendoring

• JSON-Schema-Test-Suite is vendored from commit # c1b12bf699f29a04b4286711c6e3bbfba66f21e5 here.

• src/draft4.json is from commit # c1b12bf699f29a04b4286711c6e3bbfba66f21e5 here. The root ref in remote ref test has been modified to fix #175.

• .travis.yml was created with make_travis_yml_2.hs commit # ea6c7d177a97bfbfb2fdc4deba943d60d2aff199.

Credits

TJ Weigel created the logo.

Tim Baumann wrote aeson-schema, on which hjsonschema's test code and its implementation of SchemaGraph were based.

Julian Berman maintains the fantastic language agnostic test suite.