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lib/phoenix/endpoint/render_errors.ex

defmodule Phoenix.Endpoint.RenderErrors do
# This module is used to catch failures and render them using a view.
#
# This module is automatically used in `Phoenix.Endpoint` where it
# overrides `call/2` to provide rendering. Once the error is
# rendered, the error is reraised unless it is a NoRouteError.
#
# ## Options
#
# * `:view` - the name of the view we render templates against
# * `:format` - the format to use when none is available from the request
# * `:accepts` - list of accepted formats errors will be rendered for
# * `:log` - the `t:Logger.level/0` or `false` to disable logging rendered errors
#
@moduledoc false
import Plug.Conn
require Phoenix.Endpoint
require Logger
alias Phoenix.Router.NoRouteError
alias Phoenix.Controller
@already_sent {:plug_conn, :sent}
@doc false
defmacro __using__(opts) do
quote do
@before_compile Phoenix.Endpoint.RenderErrors
@phoenix_render_errors unquote(opts)
end
end
@doc false
defmacro __before_compile__(_) do
quote location: :keep do
defoverridable [call: 2]
def call(conn, opts) do
try do
super(conn, opts)
rescue
e in Plug.Conn.WrapperError ->
%{conn: conn, kind: kind, reason: reason, stack: stack} = e
unquote(__MODULE__).__catch__(conn, kind, reason, stack, @phoenix_render_errors)
catch
kind, reason ->
stack = __STACKTRACE__
unquote(__MODULE__).__catch__(conn, kind, reason, stack, @phoenix_render_errors)
end
end
end
end
@doc false
def __catch__(conn, kind, reason, stack, opts) do
receive do
@already_sent ->
send(self(), @already_sent)
%Plug.Conn{conn | state: :sent}
after 0 ->
instrument_render_and_send(conn, kind, reason, stack, opts)
end
:erlang.raise(kind, reason, stack)
end
defp instrument_render_and_send(conn, kind, reason, stack, opts) do
level = Keyword.get(opts, :log, :debug)
status = status(kind, reason)
conn = error_conn(conn, kind, reason)
start = System.monotonic_time()
metadata = %{conn: conn, status: status, kind: kind, reason: reason, stacktrace: stack, log: level}
try do
render(conn, status, kind, reason, stack, opts)
after
duration = System.monotonic_time() - start
:telemetry.execute([:phoenix, :error_rendered], %{duration: duration}, metadata)
end
end
defp error_conn(_conn, :error, %NoRouteError{conn: conn}), do: conn
defp error_conn(conn, _kind, _reason), do: conn
## Rendering
@doc false
def __debugger_banner__(_conn, _status, _kind, %NoRouteError{router: router}, _stack) do
"""
<h3>Available routes</h3>
<pre>#{Phoenix.Router.ConsoleFormatter.format(router)}</pre>
"""
end
def __debugger_banner__(_conn, _status, _kind, _reason, _stack), do: nil
defp render(conn, status, kind, reason, stack, opts) do
view = Keyword.fetch!(opts, :view)
conn =
conn
|> maybe_fetch_query_params()
|> maybe_fetch_format(opts)
|> Plug.Conn.put_status(status)
|> Controller.put_root_layout(opts[:root_layout] || false)
|> Controller.put_layout(opts[:layout] || false)
|> Controller.put_view(view)
reason = Exception.normalize(kind, reason, stack)
format = Controller.get_format(conn)
template = "#{conn.status}.#{format}"
assigns = %{kind: kind, reason: reason, stack: stack, status: conn.status}
conn
|> Controller.put_view(view)
|> Controller.render(template, assigns)
end
defp maybe_fetch_query_params(conn) do
fetch_query_params(conn)
rescue
Plug.Conn.InvalidQueryError ->
case conn.params do
%Plug.Conn.Unfetched{} -> %Plug.Conn{conn | query_params: %{}, params: %{}}
params -> %Plug.Conn{conn | query_params: %{}, params: params}
end
end
defp maybe_fetch_format(conn, opts) do
# We ignore params["_format"] although we respect any already stored.
case conn.private do
%{phoenix_format: format} when is_binary(format) -> conn
_ -> Controller.accepts(conn, Keyword.fetch!(opts, :accepts))
end
rescue
e in Phoenix.NotAcceptableError ->
fallback_format = Keyword.fetch!(opts, :accepts) |> List.first()
Logger.debug("Could not render errors due to #{Exception.message(e)}. " <>
"Errors will be rendered using the first accepted format #{inspect fallback_format} as fallback. " <>
"Please customize the :accepts option under the :render_errors configuration " <>
"in your endpoint if you want to support other formats or choose another fallback")
Controller.put_format(conn, fallback_format)
end
defp status(:error, error), do: Plug.Exception.status(error)
defp status(:throw, _throw), do: 500
defp status(:exit, _exit), do: 500
end