# `MishkaCmsCore.Runtime.PageBuilder.CardPreviewInvalidator`
[🔗](https://github.com/mishka-group/mishka_cms_core/blob/v0.0.1/lib/mishka_cms_core/runtime/page_builder/card_preview_invalidator.ex#L5)

Drops cached palette-card previews when the component they drew has been recompiled.

A preview is markup produced by a component's module. Recompile the module and the markup can
change — and a stale one is the worst kind of wrong, because it looks fine: the author sees the
component they edited still drawn the old way and concludes their edit did not take.

Hung off `runtime:after_module_compile`, which the compiler already announces, rather than a call
wired into the compiler by hand. The core is a participant in its own events (ADR-14), so this is
the same mechanism an extension would use to react to the same fact — see
`MishkaCmsCore.Builder.Events`.

It cannot tell WHICH site's previews a module belongs to without loading it, so it drops all of
them. That is the cheap and correct trade: the cache refills at about two milliseconds an entry,
and a compile is rare next to a hover.

# `error_return`

```elixir
@type error_return() ::
  {:error, [%{action: atom(), field: atom(), message: String.t()}]}
```

# `okey_return`

```elixir
@type okey_return() :: {:ok, struct() | map() | module() | [any()]}
```

# `child_spec`

Returns a specification to start this module under a supervisor.

See `Supervisor`.

# `config`

```elixir
@spec config() :: keyword()
```

# `config`

```elixir
@spec config(atom()) :: any()
```

# `enable`

```elixir
@spec enable() :: okey_return() | error_return()
```

# `get`

```elixir
@spec get() :: keyword()
```

# `health_check`

```elixir
@spec health_check() :: :ok | {:degraded, term()} | {:error, term()}
```

Optional. See `c:MishkaInstaller.Event.Hook.health_check/0`. Override to report health.

# `on_dependency_error`

```elixir
@spec on_dependency_error(term()) :: term()
```

Optional. See `c:MishkaInstaller.Event.Hook.on_dependency_error/1`. Override to react.

# `register`

```elixir
@spec register() :: okey_return() | error_return()
```

# `restart`

```elixir
@spec restart() :: okey_return() | error_return()
```

# `start`

```elixir
@spec start() :: okey_return() | error_return()
```

# `start_link`

# `stop`

```elixir
@spec stop() :: okey_return() | error_return()
```

# `unregister`

```elixir
@spec unregister() :: okey_return() | error_return()
```

---

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