# `Soundcheck.Check.Design.UnusedEventHandler`
[🔗](https://github.com/leonqadirie/soundcheck/blob/v0.1.0/lib/soundcheck/check/design/unused_event_handler.ex#L1)

## Basics

> #### This check is disabled by default. {: .neutral}
>
> [Learn how to enable it](`e:credo:config_file.html#checks`) via `.credo.exs`.

This check has a base priority of `normal` and works with any version of Elixir.

## Explanation

Flags literal `handle_event/3` clauses that no template, `JS.push`,
or hook in the project emits to their module: dead code left behind
after a template change.

Before:

    <button phx-click="save">Save</button>

    def handle_event("save", params, socket), do: ...
    def handle_event("archive", params, socket), do: ...  # nothing emits it

After: remove the `"archive"` clause, or wire up its emitter.

The check needs a closed world to be right, so it reports nothing
unless every event emitter in the project resolves: one dynamic event
name (`phx-click={@action}`), selector target, unresolvable hook
push, or `pushEvent` with a dynamic name anywhere in the project's
JavaScript turns it off. A handler whose event name appears as a
string anywhere else in the project's Elixir code (helpers, tests), or
as a literal `pushEvent` name in its JavaScript, is never reported.

Confidence: medium. Tier: semantic (run `mix compile` before `mix credo`).

## Check-Specific Parameters

Use the following parameters to configure this check:

### `:excluded_paths`

  Paths to skip (atoms, binaries as path segments, or regexes).

*This parameter defaults to* `[~r/\/test\//, "test"]`.

### `:strict`

  Unused.

*This parameter defaults to* `false`.

### `:ignore_events`

  Event names to skip: binaries or regexes.

*This parameter defaults to* `[]`.

## General Parameters

Like with all checks, [general params](`e:credo:check_params.html`) can be applied.

Parameters can be configured via the [`.credo.exs` config file](`e:credo:config_file.html`).

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