From 818301227f6f8946e2130a43b75f3d685bc32b70 Mon Sep 17 00:00:00 2001
From: Ward Peeters <ward@coding-tech.com>
Date: Wed, 10 Mar 2021 23:47:08 +0100
Subject: [PATCH] fix(gatsyby): improve error messages for errors outside of
 react" (#30031)

---
 .../cache-dir/__tests__/ensure-resources.tsx  |  3 +++
 packages/gatsby/cache-dir/ensure-resources.js | 25 ++++++++++++++-----
 packages/gatsby/cache-dir/loader.js           | 22 ++++++++++++----
 3 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/packages/gatsby/cache-dir/__tests__/ensure-resources.tsx b/packages/gatsby/cache-dir/__tests__/ensure-resources.tsx
index 0613effcbdb04..8d5841c614fbd 100644
--- a/packages/gatsby/cache-dir/__tests__/ensure-resources.tsx
+++ b/packages/gatsby/cache-dir/__tests__/ensure-resources.tsx
@@ -4,6 +4,9 @@ import { render, getNodeText, cleanup } from "@testing-library/react"
 
 jest.mock(`../loader`, () => {
   return {
+    PageResourceStatus: {
+      Error: `error`,
+    },
     loadPageSync(path: string): { loadPageSync: boolean; path: string } {
       return { loadPageSync: true, path }
     },
diff --git a/packages/gatsby/cache-dir/ensure-resources.js b/packages/gatsby/cache-dir/ensure-resources.js
index c3232c1fab076..80bbb8d8dcdf9 100644
--- a/packages/gatsby/cache-dir/ensure-resources.js
+++ b/packages/gatsby/cache-dir/ensure-resources.js
@@ -8,13 +8,18 @@ class EnsureResources extends React.Component {
     const { location, pageResources } = props
     this.state = {
       location: { ...location },
-      pageResources: pageResources || loader.loadPageSync(location.pathname),
+      pageResources:
+        pageResources ||
+        loader.loadPageSync(location.pathname, { withErrorDetails: true }),
     }
   }
 
   static getDerivedStateFromProps({ location }, prevState) {
     if (prevState.location.href !== location.href) {
-      const pageResources = loader.loadPageSync(location.pathname)
+      const pageResources = loader.loadPageSync(location.pathname, {
+        withErrorDetails: true,
+      })
+
       return {
         pageResources,
         location: { ...location },
@@ -82,12 +87,20 @@ class EnsureResources extends React.Component {
   }
 
   render() {
-    if (process.env.NODE_ENV !== `production` && !this.state.pageResources) {
-      throw new Error(
-        `EnsureResources was not able to find resources for path: "${this.props.location.pathname}"
+    if (
+      process.env.NODE_ENV !== `production` &&
+      (!this.state.pageResources ||
+        this.state.pageResources.status === PageResourceStatus.Error)
+    ) {
+      const message = `EnsureResources was not able to find resources for path: "${this.props.location.pathname}"
 This typically means that an issue occurred building components for that path.
 Run \`gatsby clean\` to remove any cached elements.`
-      )
+      if (this.state.pageResources?.error) {
+        console.error(message)
+        throw this.state.pageResources.error
+      }
+
+      throw new Error(message)
     }
 
     return this.props.children(this.state)
diff --git a/packages/gatsby/cache-dir/loader.js b/packages/gatsby/cache-dir/loader.js
index f42da55644d5f..1a1e227718bde 100644
--- a/packages/gatsby/cache-dir/loader.js
+++ b/packages/gatsby/cache-dir/loader.js
@@ -348,12 +348,22 @@ export class BaseLoader {
     return inFlightPromise
   }
 
-  // returns undefined if loading page ran into errors
-  loadPageSync(rawPath) {
+  // returns undefined if the page does not exists in cache
+  loadPageSync(rawPath, options = {}) {
     const pagePath = findPath(rawPath)
     if (this.pageDb.has(pagePath)) {
-      const pageData = this.pageDb.get(pagePath).payload
-      return pageData
+      const pageData = this.pageDb.get(pagePath)
+
+      if (pageData.payload) {
+        return pageData.payload
+      }
+
+      if (options?.withErrorDetails) {
+        return {
+          error: pageData.error,
+          status: pageData.status,
+        }
+      }
     }
     return undefined
   }
@@ -546,7 +556,9 @@ export const publicLoader = {
   getResourceURLsForPathname: rawPath =>
     instance.getResourceURLsForPathname(rawPath),
   loadPage: rawPath => instance.loadPage(rawPath),
-  loadPageSync: rawPath => instance.loadPageSync(rawPath),
+  // TODO add deprecation to v4 so people use withErrorDetails and then we can remove in v5 and change default behaviour
+  loadPageSync: (rawPath, options = {}) =>
+    instance.loadPageSync(rawPath, options),
   prefetch: rawPath => instance.prefetch(rawPath),
   isPageNotFound: rawPath => instance.isPageNotFound(rawPath),
   hovering: rawPath => instance.hovering(rawPath),