# `Soundcheck.Check.Warning.CrashingMatchInCallback`
[🔗](https://github.com/leonqadirie/soundcheck/blob/v0.1.0/lib/soundcheck/check/warning/crashing_match_in_callback.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 tagged-tuple matches on a call's result, such as
`{:ok, post} = Blog.update_post(...)`, in LiveView and LiveComponent
callbacks. When the call returns anything else, the match raises, the
LiveView process crashes, and the browser remounts it: the user sees
a flash of reloading and loses unsaved state, such as form input.

Before:

    def handle_event("save", %{"post" => params}, socket) do
      {:ok, post} = Blog.update_post(socket.assigns.post, params)
      {:noreply, assign(socket, :post, post)}
    end

After:

    def handle_event("save", %{"post" => params}, socket) do
      case Blog.update_post(socket.assigns.post, params) do
        {:ok, post} -> {:noreply, assign(socket, :post, post)}
        {:error, changeset} -> {:noreply, assign(socket, :form, to_form(changeset))}
      end
    end

The check looks at `mount/3`, `handle_params/3`, `handle_event/3`,
`handle_info/2`, `handle_async/3`, and `update/2`, and at matches
whose left side is a tuple tagged with an atom (`{:ok, _}`,
`{:error, _}`, `{:ok, _, _}`) and whose right side is a function call
or a pipe ending in one. Matches inside anonymous functions are
skipped: they run elsewhere, such as in `start_async/3`. Helpers the
callbacks call are not followed. A match that should crash, because
failure means a bug, is fine; silence it with a
`soundcheck:disable-next-line SC603` comment that says so.

Confidence: medium. Tier: syntactic (works without compiling).

## 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`.

## 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*