Merge pull request #365 from haskellfoundation/404

Add a GitHub Pages 404 page

Author: david-christiansen

message-index/404.html

@@ -0,0 +1,12 @@
+---
+title: The Haskell Error Index
+---
+
+<div id="documentation-pointer">Page not found.</div>
+
+<script>
+const messageRe = /^\/messages\/[A-Z]+-[0-9]+/;
+if messageRe.test(window.location.pathname) {
+  document.getElementById("documentation-pointer").innerHTML = "This message is currently undocumented. You can help out by <a href=\"https://github.com/haskellfoundation/error-message-index/issues\">opening an issue</a> or <a href=\"https://github.com/haskellfoundation/error-message-index/pulls\">contributing documentation</a>."
+}
+</script>

message-index/site.hs

@@ -115,6 +115,16 @@ main = hakyll $ do
     route $ setExtension "html"
     compile $ makeItem $ Redirect "/"
 
+  match "404.html" $ do
+    route idRoute
+    compile $ do
+      bread <- breadcrumbField ["index.html"]
+      let ctx = mconcat [constField "title" "Not Found", bread, defaultContext]
+      getResourceBody
+        >>= applyAsTemplate ctx
+        >>= loadAndApplyTemplate "templates/default.html" ctx
+        >>= relativizeUrls
+
   match "index.html" $
     version "nav" $ do
       route idRoute