[source-contentful] offline mode

packages/gatsby-source-contentful/README.md

@@ -44,6 +44,11 @@ plugins: [
 ]
 ```
 
+### Offline
+
+If you don't have internet connection you can add `export GATSBY_CONTENTFUL_OFFLINE=true` to tell the plugin to fallback to the cached data, if there is any.
+
+
 ### Configuration options
 
 **`spaceId`** [string][required]

packages/gatsby-source-contentful/package.json

@@ -14,6 +14,7 @@
     "contentful": "^6.1.0",
     "deep-map": "^1.5.0",
     "fs-extra": "^4.0.2",
+    "is-online": "^7.0.0",
     "gatsby-plugin-sharp": "^2.0.0-beta.2",
     "json-stringify-safe": "^5.0.1",
     "lodash": "^4.17.4",

packages/gatsby-source-contentful/src/fetch.js

@@ -1,6 +1,5 @@
 const contentful = require(`contentful`)
 const _ = require(`lodash`)
-
 const normalize = require(`./normalize`)
 
 module.exports = async ({
@@ -10,8 +9,9 @@ module.exports = async ({
   syncToken,
   environment,
 }) => {
-  // Fetch articles.
+  // Fetch entries.
   console.time(`Fetch Contentful data`)
+
   console.log(`Starting to fetch data from Contentful`)
 
   const client = contentful.createClient({
@@ -36,9 +36,10 @@ module.exports = async ({
     console.log(
       `Accessing your Contentful space failed. Perhaps you're offline or the spaceId/accessToken is incorrect.`
     )
-    // TODO perhaps continue if there's cached data? That would let
-    // someone develop a contentful site even if not connected to the internet.
-    // For prod builds though always fail if we can't get the latest data.
+    console.log(
+      `Try running setting GATSBY_CONTENTFUL_OFFLINE=true to see if we can serve from cache.`
+    )
+
     process.exit(1)
   }
 
@@ -91,12 +92,14 @@ module.exports = async ({
     return null
   })
 
-  return {
+  const result = {
     currentSyncData,
     contentTypeItems,
     defaultLocale,
     locales,
   }
+
+  return result
 }
 
 /**

packages/gatsby-source-contentful/src/gatsby-node.js

@@ -1,5 +1,5 @@
 const path = require(`path`)
-
+const isOnline = require(`is-online`)
 const _ = require(`lodash`)
 const fs = require(`fs-extra`)
 
@@ -37,6 +37,27 @@ exports.sourceNodes = async (
 ) => {
   const { createNode, deleteNode, touchNode, setPluginStatus } = actions
 
+  const online = await isOnline()
+
+  // If the user knows they are offline, serve them cached result
+  // For prod builds though always fail if we can't get the latest data
+  if (
+    !online &&
+    process.env.GATSBY_CONTENTFUL_OFFLINE === `true` &&
+    process.env.NODE_ENV !== `production`
+  ) {
+    getNodes()
+      .filter(n => n.internal.owner === `gatsby-source-contentful`)
+      .forEach(n => touchNode({ nodeId: n.id }))
+
+    console.log(`Using Contentful Offline cache ⚠️`)
+    console.log(
+      `Cache may be invalidated if you edit package.json, gatsby-node.js or gatsby-config.js files`
+    )
+
+    return
+  }
+
   host = host || `cdn.contentful.com`
   environment = environment || `master` // default is always master
   // Get sync token if it exists.
@@ -62,8 +83,8 @@ exports.sourceNodes = async (
     syncToken,
     spaceId,
     accessToken,
-    environment,
     host,
+    environment,
   })
 
   const entryList = normalize.buildEntryList({