# `MishkaCmsCore.Runtime.Resources.Mixins.VersionReach`
[🔗](https://github.com/mishka-group/mishka_cms_core/blob/v0.0.1/lib/mishka_cms_core/runtime/resources/__mixins/version_reach.ex#L5)

Who reads a runtime resource's versions — the policies of the version resources AshPaperTrail
generates.

A version is a copy of its record, so it is read as the record is: by anyone under the request's
surface, and by a master (`site_id` nil) on any site, by a site user on its own site — and, with
`shared?: true`, on the shared records too — through whichever read it asks, `:read_any`
included. Anybody else, a missing actor included, reads none. System reads pass
`authorize?: false`; AshPaperTrail writes versions without authorization.

Versions loaded through their record — its `:sorted_versions` or AshPaperTrail's
`:paper_trail_versions` — are the record's own, so the read that reached the record decides: a
record's reads build the versions query ahead of the load, and Ash runs such a query with no
actor.

The version resource takes the authorizer through the source resource's `version_extensions`,
and its mixin quotes these policies into its body:

    paper_trail do
      version_extensions authorizers: [Ash.Policy.Authorizer]
      mixin {MishkaCmsCore.Runtime.Resources.Mixins.LayoutPaperTrailMixin, :postgres, []}
    end

    # in the mixin's quoted body
    unquote(
      MishkaCmsCore.Runtime.Resources.Mixins.VersionReach.policies(
        source: MishkaCmsCore.Runtime.Layout,
        shared?: true
      )
    )

## Options

  * `:source` — the versioned resource. Required.
  * `:shared?` — whether the resource has shared (`site_id` nil) records a site user reads.
    Defaults to `false`.

# `policies`

```elixir
@spec policies(keyword()) :: Macro.t()
```

The quoted `policies` block for a version resource.

---

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