# Upgrading a host from 0.4 to 0.5

This page says what a host changes to move `statifier_datamodel` from
0.4.0 to 0.5.0, and on to the 0.5.1 patch. A host here is the code that
embeds the package: the datamodel documents it writes, the calls it makes
to `StatifierDatamodel.Index`, `StatifierDatamodel.Document`,
`StatifierDatamodel.Declarations`, `StatifierDatamodel.Types`,
`StatifierDatamodel.Compatibility` and `StatifierDatamodel.Coverage`, and
any relation of its own it wraps around the read check. What each release
added is in [CHANGELOG.md](../CHANGELOG.md); this page lists only what a
host has to do about it, and says **NONE** where the answer is nothing.

Move the pin with the minor, as the README recommends:
`{:statifier_datamodel, "~> 0.5.0"}`. The Elixir requirement
(`~> 1.18`) is the same on both sides of this page, and the package still
has no runtime dependencies. A host that takes this package through
`statifier_blocks` or `statifier_ui` need not move either of them with
it: statifier_blocks from 0.35.0 through 0.42.1 and statifier_ui 0.10.1
and 0.10.2 each require `~> 0.4`, which admits 0.5.

## 0.4 to 0.5

Must change: **NONE**. 0.5.0 adds one module and one shipped file and
changes no existing signature or answer: `StatifierDatamodel.Index.index/1`
answers exactly as before for every document, and no module other than the
new one gains or loses a function.

May start doing:

- **Validate a document before you index it.** The package now ships a
  hand-written draft-07 JSON Schema of the version-1 datamodel document,
  `priv/schemas/datamodel-document.schema.json`, in the tarball a host
  fetches. `StatifierDatamodel.Schema.path/0` answers where it is
  installed and `StatifierDatamodel.Schema.json/0` answers its text (the
  text, not a decoded map). Hand it to the draft-07 validator your own
  language already has. The schema is advisory: nothing in the package
  calls it, and it is deliberately stricter than `index/1`, so a document
  the schema rejects still indexes as it always did. What it rejects is
  yours to read and to give a severity; the `StatifierDatamodel.Schema`
  documentation lists the kinds of slip it catches.

Worth knowing, with no change to make:

- **If you wrap `StatifierDatamodel.Types.satisfies/3` in a relation of
  your own**, the `StatifierDatamodel.Types` documentation now states the
  rule such a wrapper keeps: whenever `satisfies/3` answers not-satisfied,
  the wrapper answers not-satisfied too. It also says reasons in
  `t:StatifierDatamodel.Types.reason/0` may be added as records take
  decisions, so match the reasons you render and send anything else to a
  default clause. No reason was added or re-spelled in 0.5.0; this is
  documentation of what a wrapper may rely on, not a change to the check.

## 0.5.0 to 0.5.1

Must change: **NONE**. 0.5.1 is a documentation release: the code and the
shipped schema are unchanged from 0.5.0. `~> 0.5.0` already takes it.