From 128f0d1bb6c141512fd94d63b890caa375c22253 Mon Sep 17 00:00:00 2001
From: Szymon Nowak <szimek@gmail.com>
Date: Mon, 29 Jan 2018 19:15:08 +0100
Subject: [PATCH] [gatsby] Report an error when layout file is missing (#3762)

* [gatsby] Report an error when layout file is missing

* Update pages-writer.js

* format
---
 packages/gatsby/src/bootstrap/index.js              |  6 +++++-
 .../internal-plugins/query-runner/pages-writer.js   | 13 ++++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/packages/gatsby/src/bootstrap/index.js b/packages/gatsby/src/bootstrap/index.js
index e57f841b691e1..a5e16b401a349 100644
--- a/packages/gatsby/src/bootstrap/index.js
+++ b/packages/gatsby/src/bootstrap/index.js
@@ -357,7 +357,11 @@ module.exports = async (args: BootstrapArgs) => {
   // Write out files.
   activity = report.activityTimer(`write out page data`)
   activity.start()
-  await writePages()
+  try {
+    await writePages()
+  } catch (err) {
+    report.panic(`Failed to write out page data`, err)
+  }
   activity.end()
 
   // Write out redirects.
diff --git a/packages/gatsby/src/internal-plugins/query-runner/pages-writer.js b/packages/gatsby/src/internal-plugins/query-runner/pages-writer.js
index f11ac7f746095..b74bc04797344 100644
--- a/packages/gatsby/src/internal-plugins/query-runner/pages-writer.js
+++ b/packages/gatsby/src/internal-plugins/query-runner/pages-writer.js
@@ -43,6 +43,15 @@ const writePages = async () => {
     })
     if (p.layout) {
       let layout = getLayoutById(layouts)(p.layout)
+
+      if (!layout) {
+        throw new Error(
+          `Could not find layout '${
+            p.layout
+          }'. Check if this file exists in 'src/layouts'.`
+        )
+      }
+
       pageLayouts.push(layout)
       json.push({
         jsonName: layout.jsonName,
@@ -122,7 +131,7 @@ const preferDefault = m => m && m.default || m
     .join(`,\n`)}
 }`
 
-  await Promise.all([
+  return await Promise.all([
     fs.writeFile(
       joinPath(program.directory, `.cache/pages.json`),
       JSON.stringify(pagesData, null, 4)
@@ -133,8 +142,6 @@ const preferDefault = m => m && m.default || m
       asyncRequires
     ),
   ])
-
-  return
 }
 
 exports.writePages = writePages