# `mix riddler.corpus`
[🔗](https://github.com/riddler/riddler-ex/blob/v0.4.0/lib/mix/tasks/riddler.corpus.ex#L1)

Exports the conformance corpus and the JSON schemas out of this repository
into a directory you name, or checks that the copy already in that directory
is the one this repository would write.

    mix riddler.corpus --to ../export
    mix riddler.corpus --check --to ../export

The corpus lives in this repository: the cases in `corpus/`, beside the code
that has to satisfy them, and the schemas in `priv/schemas/`. A runtime in
another language vendors them from a tag of this repository. This task is for
a consumer that wants a copy as files, and the copy is an artifact. So the
task runs every case through this implementation before it writes anything
and refuses on the first red case: a corpus copied out of a repository whose
own suite it does not describe would hold a second runtime to behavior the
reference runtime does not have.

What is written is byte-stable - keys sorted, two spaces of indent, one
trailing newline, no version, no timestamp and no commit - so re-exporting an
unchanged corpus writes the same bytes and `--check` reports a real change
rather than the passage of time or the cutting of a release. Each case file
gains one key it was not authored with, `generated_by`, whose value is the
word `riddler`, a space, the word `from`, a space and the file's path in this
repository - `"riddler from corpus/screens/admit.json"`. The schemas are
copied unchanged.

## Where it writes

Into the `--to` directory, and nowhere else: there is no default and no
environment variable, and the task refuses to run without `--to`. A case file
lands at `<path>/corpus/<capability>/<name>.json` and a schema at
`<path>/schemas/<name>.schema.json`.

## Options

  * `--to PATH` - required. The directory to export into, or, with
    `--check`, the directory holding the copy to compare.
  * `--check` - writes nothing. Compares what would be written against what
    is there and exits 1 listing every file that is missing or differs.
  * `--force` - write even though the target is a git working tree with
    uncommitted changes. Without it an export onto a dirty tree is refused,
    because the export overwrites whole files and git is what would
    otherwise give the work back. `--check` writes nothing and never refuses.

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*Consult [api-reference.md](api-reference.md) for complete listing*