feat: try to generate stable build ids (#606)

Author: ascorbic

.gitignore

@@ -149,6 +149,9 @@ Temporary Items
 .apdisk
 
 # End of https://www.toptal.com/developers/gitignore/api/osx,node
+
 demo/package-lock.json
+# We generate this on build in the demo
+demo/next.config.js
 
 .netlify

demo/next.config.js

@@ -12,7 +12,18 @@ const verifyBuildTarget = async ({ failBuild, netlifyConfig }) => {
 
   const { target, configFile } = await getNextConfig(failBuild, nextRoot)
 
-  // If the next config exists, log warning if target isnt in acceptableTargets
+  if (!configFile) {
+    await writeFile(
+      path.resolve(nextRoot, 'next.config.js'),
+      `module.exports = {
+  // Supported targets are "serverless" and "experimental-serverless-trace"
+  target: "serverless",
+  generateBuildId: () => "build"
+}`,
+    )
+  }
+
+  // If the next config exists, log warning if target isn't in acceptableTargets
   const acceptableTargets = ['serverless', 'experimental-serverless-trace']
   const isValidTarget = acceptableTargets.includes(target)
   if (isValidTarget) {
@@ -49,18 +60,6 @@ const verifyBuildTarget = async ({ failBuild, netlifyConfig }) => {
   // Clear memoized cache
   getNextConfig.clear()
 
-  // Creating a config file, because otherwise Next won't reload the config and pick up the new target
-
-  if (!configFile) {
-    await writeFile(
-      path.resolve(nextRoot, 'next.config.js'),
-      `
-module.exports = {
-  // Supported targets are "serverless" and "experimental-serverless-trace"
-  target: "serverless"
-}`,
-    )
-  }
   // Force the new config to be generated
   await getNextConfig(failBuild, nextRoot)
   // Reset the value in case something else is looking for it

helpers/verifyBuildTarget.js

@@ -1,7 +1,7 @@
 const { readdirSync, existsSync } = require('fs')
 const path = require('path')
 
-const { yellowBright, greenBright } = require('chalk')
+const { yellowBright, greenBright, green } = require('chalk')
 const makeDir = require('make-dir')
 const { satisfies } = require('semver')
 const glob = require('tiny-glob')
@@ -140,12 +140,24 @@ See https://ntl.fyi/remove-plugin for instructions.
     const nextRoot = getNextRoot({ netlifyConfig })
 
     const nextConfig = await getNextConfig(utils.failBuild, nextRoot)
-    await saveCache({ cache: utils.cache, distDir: nextConfig.distDir, nextRoot })
+    const { distDir, generateBuildId } = nextConfig
+    await saveCache({ cache: utils.cache, distDir, nextRoot })
     copyUnstableIncludedDirs({ nextConfig, functionsDist: path.resolve(FUNCTIONS_DIST) })
     utils.status.show({
       title: 'Essential Next.js Build Plugin ran successfully',
       summary: 'Generated serverless functions and stored the Next.js cache',
     })
+
+    // The default generateBuildId function returns null, which causes it to use a random value from nanoid
+    // eslint-disable-next-line no-self-compare
+    if (generateBuildId() === null || generateBuildId() !== generateBuildId()) {
+      console.warn(
+        yellowBright`
+For faster deploy times, build IDs should be set to a static value.
+To do this, set ${green`generateBuildId: () => 'build'`} in your next.config.js`,
+        // TODO: add shortlink when docs are updated
+      )
+    }
   },
 }