fix: allow atom layout module names (#108)

String values for layout module names are required to be supported in
the front matter, but it feels odd to require that they be strings in
config. This enables the specification of layout modules as atoms and
fixes a bug in PageExtension which required a layout value in the
front matter at all times.

Author: halostatue

lib/tableau/extensions/page_extension.ex

@@ -73,7 +73,7 @@ defmodule Tableau.PageExtension do
         optional(:enabled, true) => bool(),
         optional(:dir, "_pages") => str(),
         optional(:permalink) => str(),
-        optional(:layout) => str()
+        optional(:layout) => oneof([str(), atom()])
       }),
       input
     )
@@ -113,7 +113,7 @@ defmodule Tableau.PageExtension do
     |> Map.put(:__tableau_page_extension__, true)
     |> Map.put(:body, body)
     |> Map.put(:file, filename)
-    |> Map.put(:layout, Module.concat([front_matter.layout || pages_config.layout]))
+    |> Map.put(:layout, Module.concat([front_matter[:layout] || pages_config.layout]))
     |> Common.build_permalink(pages_config)
   end
 end

lib/tableau/extensions/post_extension.ex

@@ -81,7 +81,7 @@ defmodule Tableau.PostExtension do
         optional(:dir, "_posts") => str(),
         optional(:future, false) => bool(),
         optional(:permalink) => str(),
-        optional(:layout) => str()
+        optional(:layout) => oneof([atom(), str()])
       }),
       config
     )

test/tableau/extensions/page_extension_test.exs

@@ -13,7 +13,7 @@ defmodule Tableau.PageExtensionTest do
 
   describe "run" do
     setup %{tmp_dir: dir} do
-      assert {:ok, config} = PageExtension.config(%{dir: dir, enabled: true})
+      assert {:ok, config} = PageExtension.config(%{dir: dir, enabled: true, layout: Blog.DefaultPageLayout})
 
       token = %{
         site: %{config: %{converters: [md: Tableau.MDExConverter]}},
@@ -200,5 +200,33 @@ defmodule Tableau.PageExtensionTest do
                ]
              } = token
     end
+
+    test "inherits layout from page extension config", %{tmp_dir: dir, token: token} do
+      File.write(Path.join(dir, "a-page.md"), """
+      ---
+      title: missing layout key
+      type: articles
+      permalink: /:type/:title
+      ---
+
+      A great page
+      """)
+
+      assert {:ok, token} = PageExtension.run(token)
+
+      assert %{
+               pages: [
+                 %{
+                   __tableau_page_extension__: true,
+                   body: "\nA great page\n",
+                   file: ^dir <> "/a-page.md",
+                   layout: Blog.DefaultPageLayout,
+                   permalink: "/articles/missing-layout-key",
+                   title: "missing layout key",
+                   type: "articles"
+                 }
+               ]
+             } = token
+    end
   end
 end

test/tableau/extensions/post_extension_test.exs

@@ -13,7 +13,7 @@ defmodule Tableau.PostExtensionTest do
 
   describe "run" do
     setup %{tmp_dir: dir} do
-      assert {:ok, config} = PostExtension.config(%{dir: dir, enabled: true})
+      assert {:ok, config} = PostExtension.config(%{dir: dir, enabled: true, layout: Blog.DefaultPostLayout})
 
       token = %{
         site: %{config: %{converters: [md: Tableau.MDExConverter]}},
@@ -233,6 +233,34 @@ defmodule Tableau.PostExtensionTest do
              } = token
     end
 
+    test "inherits layout from post extension config", %{tmp_dir: dir, token: token} do
+      File.write(Path.join(dir, "a-post.md"), """
+      ---
+      title: Missing layout key
+      date: 2018-02-28
+      permalink: /:title
+      ---
+
+      A great post
+      """)
+
+      assert {:ok, token} = PostExtension.run(token)
+
+      assert %{
+               posts: [
+                 %{
+                   __tableau_post_extension__: true,
+                   body: "\nA great post\n",
+                   date: ~U[2018-02-28 00:00:00Z],
+                   file: ^dir <> "/a-post.md",
+                   layout: Blog.DefaultPostLayout,
+                   permalink: "/missing-layout-key",
+                   title: "Missing layout key"
+                 }
+               ]
+             } = token
+    end
+
     test "handles frontmatter data in the permalink", %{tmp_dir: dir, token: token} do
       File.write(Path.join(dir, "a-post.md"), """
       ---