Merge pull request #114 from netlify/chore/refactor-get-next-config

chore: separate `getNextConfig()`

helpers/getNextConfig.js

@@ -0,0 +1,26 @@
+const { resolve } = require('path')
+
+let nextConfig
+
+// Load next.config.js
+const getNextConfig = async function (failBuild) {
+  // Memoizes `nextConfig`
+  if (nextConfig !== undefined) {
+    return nextConfig
+  }
+
+  // We cannot load `next` at the top-level because we validate whether the
+  // site is using `next` inside `onPreBuild`.
+  const { PHASE_PRODUCTION_BUILD } = require('next/constants')
+  const loadConfig = require('next/dist/next-server/server/config').default
+
+  try {
+    nextConfig = await loadConfig(PHASE_PRODUCTION_BUILD, resolve('.'))
+  } catch (error) {
+    return failBuild('Error loading your next.config.js.', { error })
+  }
+
+  return nextConfig
+}
+
+module.exports = getNextConfig

helpers/hasCorrectNextConfig.js

@@ -1,27 +1,18 @@
-const path = require('path')
+const getNextConfig = require('./getNextConfig')
 
-// Checks if site has the correct next.cofig.js
+// Checks if site has the correct next.config.js
 const hasCorrectNextConfig = async ({ nextConfigPath, failBuild }) => {
   // In the plugin's case, no config is valid because we'll make it ourselves
   if (nextConfigPath === undefined) return true
 
-  // We cannot load `next` at the top-level because we validate whether the
-  // site is using `next` inside `onPreBuild`.
-  const { PHASE_PRODUCTION_BUILD } = require('next/constants')
-  const { default: loadConfig } = require('next/dist/next-server/server/config')
+  const { target } = await getNextConfig(failBuild)
 
   // If the next config exists, log warning if target isnt in acceptableTargets
   const acceptableTargets = ['serverless', 'experimental-serverless-trace']
-  let nextConfig
-  try {
-    nextConfig = await loadConfig(PHASE_PRODUCTION_BUILD, path.resolve('.'))
-  } catch (error) {
-    return failBuild('Error loading your next.config.js.', { error })
-  }
-  const isValidTarget = acceptableTargets.includes(nextConfig.target)
+  const isValidTarget = acceptableTargets.includes(target)
   if (!isValidTarget) {
     console.log(
-      `Your next.config.js must set the "target" property to one of: ${acceptableTargets.join(', ')}. Update the 
+      `Your next.config.js must set the "target" property to one of: ${acceptableTargets.join(', ')}. Update the
       target property to allow this plugin to run.`,
     )
   }