Extract handle_errors to allow composition (#41)

* extract handle_errors to allow composition
* remove compilation warning in tests

Author: nirev

README.md

@@ -1,4 +1,4 @@
-# Plugsnag 
+# Plugsnag
 ![Elixir CI](https://github.com/bugsnag-elixir/plugsnag/workflows/Elixir%20CI/badge.svg)
 [![Plugsnag version](https://img.shields.io/hexpm/v/plugsnag.svg)](https://hex.pm/packages/plugsnag)
 [![Hex.pm](https://img.shields.io/hexpm/dt/plugsnag.svg)](https://hex.pm/packages/plugsnag)
@@ -17,29 +17,30 @@ Just throw it in your deps in your `mix.exs`:
 ```
 
 Then you'll need to configure it with your API key as
-per [the bugsnag-elixir
-docs](https://github.com/jarednorman/bugsnag-elixir).
+per [the bugsnag-elixir docs](https://github.com/jarednorman/bugsnag-elixir).
 
-If you're using Elixir < 1.4 make sure that `plugsnag` and `bugsnag` apps are started in your mix.exs. If you are using Elixir 1.4, the applications will be automatically started because they are dependencies.
-
-For example:
+To use the plug, `use` it in your router. For example in an Phoenix app:
 
 ```elixir
-def application do
-    [mod: {MyApp, []},
-     applications: [:logger, :plugsnag, :bugsnag]
-    ]
-  end
+defmodule YourApp.Router do
+  use Phoenix.Router
+  use Plugsnag
+
+  # ...
+end
 ```
 
-To use the plug, `use` it in your router. For example in an Phoenix app:
+If you want to define your own `handle_errors` functions using [Plug.ErrorHandler](https://hexdocs.pm/plug/Plug.ErrorHandler.html), then you can call `Plugsnag.handle_errors/{2,3}` directly.
 
 ```elixir
 defmodule YourApp.Router do
   use Phoenix.Router
-  use Plugsnag
-
+  use Plug.ErrorHandler
   # ...
+  defp handle_errors(conn, assigns) do
+    Plugsnag.handle_errors(conn, assigns)
+    # do your own handling
+  end
 end
 ```
 

lib/plugsnag.ex

@@ -3,36 +3,36 @@ defmodule Plugsnag do
     quote location: :keep do
       use Plug.ErrorHandler
 
-      defp handle_errors(conn, %{reason: exception, kind: :error} = assigns) do
-        # Only handle exceptions that get rendered as an HTTP 5xx status
-        if Plug.Exception.status(exception) >= 500 do
-          do_handle_errors(conn, assigns)
-        end
+      defp handle_errors(conn, assigns) do
+        Plugsnag.handle_errors(conn, assigns, unquote(options))
       end
+    end
+  end
 
-      defp handle_errors(conn, %{reason: _exception} = assigns) do
-        do_handle_errors(conn, assigns)
-      end
+  def handle_errors(conn, assigns, opts \\ [])
+
+  def handle_errors(conn, %{reason: exception, kind: :error} = assigns, opts) do
+    # Only handle exceptions that get rendered as an HTTP 5xx status
+    if Plug.Exception.status(exception) >= 500 do
+      report_error(conn, assigns, opts)
+    end
+  end
 
-      defp do_handle_errors(conn, %{reason: exception}) do
-        error_report_builder =
-          unquote(
-            Keyword.get(
-              options,
-              :error_report_builder,
-              Plugsnag.BasicErrorReportBuilder
-            )
-          )
+  def handle_errors(conn, %{reason: _exception} = assigns, opts) do
+    report_error(conn, assigns, opts)
+  end
 
-        options =
-          %Plugsnag.ErrorReport{}
-          |> error_report_builder.build_error_report(conn)
-          |> Map.from_struct()
-          |> Keyword.new()
+  defp report_error(conn, %{reason: exception}, opts) do
+    error_report_builder =
+      Keyword.get(opts, :error_report_builder, Plugsnag.BasicErrorReportBuilder)
 
-        reporter = Application.get_env(:plugsnag, :reporter, Bugsnag)
-        apply(reporter, :report, [exception | [options]])
-      end
-    end
+    options =
+      %Plugsnag.ErrorReport{}
+      |> error_report_builder.build_error_report(conn)
+      |> Map.from_struct()
+      |> Keyword.new()
+
+    reporter = Application.get_env(:plugsnag, :reporter, Bugsnag)
+    apply(reporter, :report, [exception | [options]])
   end
 end

test/plugsnag_test.exs

@@ -14,10 +14,12 @@ defmodule PlugsnagTest do
     defmacro __using__(_env) do
       quote do
         def call(conn, _opts) do
+          {:current_stacktrace, [_ | stacktrace]} = Process.info(self(), :current_stacktrace)
+
           raise Plug.Conn.WrapperError,
             conn: conn,
             kind: :error,
-            stack: System.stacktrace(),
+            stack: stacktrace,
             reason: TestException.exception([])
         end
       end
@@ -28,10 +30,12 @@ defmodule PlugsnagTest do
     defmacro __using__(_env) do
       quote do
         def call(conn, _opts) do
+          {:current_stacktrace, [_ | stacktrace]} = Process.info(self(), :current_stacktrace)
+
           raise Plug.Conn.WrapperError,
             conn: conn,
             kind: :error,
-            stack: System.stacktrace(),
+            stack: stacktrace,
             reason: NotFoundException.exception([])
         end
       end
@@ -69,6 +73,27 @@ defmodule PlugsnagTest do
       assert_received {:report, {%TestException{}, _}}
     end
 
+    test "calling Plugsnag.handle_errors explicitly" do
+      defmodule ExtendedPlug do
+        use Plug.ErrorHandler
+        use ErrorRaisingPlug
+
+        defp handle_errors(conn, %{reason: _exception} = assigns) do
+          send(self(), :custom_handle)
+          Plugsnag.handle_errors(conn, assigns)
+        end
+      end
+
+      conn = conn(:get, "/")
+
+      assert_raise Plug.Conn.WrapperError, "** (PlugsnagTest.TestException) oops", fn ->
+        ExtendedPlug.call(conn, [])
+      end
+
+      assert_received :custom_handle
+      assert_received {:report, {%TestException{}, _}}
+    end
+
     test "includes connection metadata in the report" do
       conn = conn(:get, "/?hello=computer")