404 Error Handling Inside Plug?

Easiest way is to call the error view render function with whatever code you want then halt() the pipeline.

Probably more correct ways, but that would work.

How can i check its halted or not , currently inside the call/2 i am doing like follow

    body = "oops not found"
    conn
    |> put_resp_content_type("application/json")
    |> send_resp(404, body)
    |> halt

You could write a controller test that looks something like the following

test "this thing halts", %{conn: conn} do
  conn = get(conn, some_path(conn, :index)
  assert conn.halted
end

this is the right answer

def call(conn, _) do
  case logics(...) do
    :ok -> conn  
    :error ->
      conn
      |> Phoenix.Controller.render(MyApp.Web.ErrorView, :"404")
      |> halt()
  end
end

Passing an atom to Phoenix.Controller.render will handle the content negation and render the html/json/etc template.

when i am trying to pass halt in pipes like follow

conn
|> Phoenix.Controller.render(XXXX.Api.V1.ErrorView, :“404error”)
|> halt()

it continues to call another plug, why doesn’t it work, ?

Mistake from my side only, this code works now

 conn = conn
            |>  Phoenix.Controller.render(XXXX.Api.V1.ErrorView, :"404error")
            |>  halt()