Capture errors with Plug.Debugger

Author: quexpl

lib/mix/tasks/tableau.build.ex

@@ -44,12 +44,17 @@ defmodule Mix.Tasks.Tableau.Build do
     pages =
       pages
       |> Task.async_stream(fn {mod, page} ->
-        content = Tableau.Document.render(graph, mod, token, page)
-        permalink = Nodable.permalink(mod)
-
-        Map.merge(page, %{body: content, permalink: permalink})
+        try do
+          content = Tableau.Document.render(graph, mod, token, page)
+          permalink = Nodable.permalink(mod)
+
+          Map.merge(page, %{body: content, permalink: permalink})
+        rescue
+          exception ->
+            reraise Tableau.BuildException, [page: page, exception: exception], __STACKTRACE__
+        end
       end)
-      |> Stream.map(fn {:ok, result} -> result end)
+      |> Stream.map(&map_pages/1)
       |> Enum.to_list()
 
     token = put_in(token.site[:pages], pages)
@@ -74,6 +79,12 @@ defmodule Mix.Tasks.Tableau.Build do
     token
   end
 
+  defp map_pages({:ok, result}), do: result
+
+  defp map_pages({:exit, {exception, stacktrace}}) do
+    reraise exception, stacktrace
+  end
+
   @file_extensions [".html"]
   defp build_file_path(out, permalink) do
     if Path.extname(permalink) in @file_extensions do

lib/tableau.ex

@@ -51,3 +51,29 @@ defmodule Tableau do
     MDEx.to_html!(content, Keyword.merge(config.markdown[:mdex], overrides))
   end
 end
+
+defmodule Tableau.BuildException do
+  @moduledoc false
+  @type t :: %__MODULE__{
+          page: map(),
+          exception: any()
+        }
+
+  defexception [:page, :exception]
+
+  @impl true
+  def exception(page: page, exception: exception) do
+    %__MODULE__{page: page, exception: exception}
+  end
+
+  @impl true
+  def message(%__MODULE__{page: page, exception: exception}) do
+    """
+    An exception was raised:
+      #{Exception.format_banner(:error, exception)}
+
+    occurred during the build process on the page:
+      #{inspect(page, pretty: true)}
+    """
+  end
+end

lib/tableau_dev_server/router.ex

@@ -1,6 +1,7 @@
 defmodule TableauDevServer.Router do
   @moduledoc false
   use Plug.Router, init_mode: :runtime
+  use Plug.Debugger
 
   require Logger