# `Mutare.Phoenix.Swoosh.LayoutConfigured`
[🔗](https://github.com/foxbenjaminfox/mutare_phoenix_swoosh/blob/v0.2.1/lib/mutare/phoenix/swoosh/layout_configured.ex#L1)

A marker `Mutare.Phoenix.Swoosh` injects for a mailer whose `use Phoenix.Swoosh` line
configures a layout (`layout: {LayoutView, :email}`).

It is **not a behaviour anyone implements**. Mutare's `use` expansion records the behaviours a
`use` injects and passes them to mutators as `context.behaviours`; this package's extension
adds this module to that set to indicate a configured layout to `Mutare.Phoenix.Swoosh.Layout`.
Nothing else reads it: the marker never reaches the metamutant source, the compiled program,
or the report.

This uses Mutare's module-scoped behaviour set, with two consequences:
the marker does not apply to a *nested* module's calls (behaviours never inherit
inwards), and a run with `--no-expand-uses` drops the injected half altogether. In both cases
`off` is generated only when the call contains an author-written truthy `layout:` assign.

It exists because the `use` line itself is unreachable — `use` options are compile-time
configuration, pruned whole before any mutation could be delivered (see the "What's
deliberately out of scope" section of the README). The marker records that configuration
for use when mutating runtime calls. Without a layout in effect, suppressing one would
produce an equivalent mutant.

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