From dcbfbde89484393c4c006fbe7a9030e0ca6e35c3 Mon Sep 17 00:00:00 2001
From: SukkaW <isukkaw@gmail.com>
Date: Mon, 18 Jul 2022 23:18:05 +0800
Subject: [PATCH] feat: show a warning about unrecognized `export config`

---
 .../build/analysis/extract-const-value.ts     |  4 ++--
 .../build/analysis/get-page-static-info.ts    | 24 ++++++++++++++++---
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/packages/next/build/analysis/extract-const-value.ts b/packages/next/build/analysis/extract-const-value.ts
index edfb89ea5e29..0cca5dfaba89 100644
--- a/packages/next/build/analysis/extract-const-value.ts
+++ b/packages/next/build/analysis/extract-const-value.ts
@@ -129,8 +129,8 @@ function isTemplateLiteral(node: Node): node is TemplateLiteral {
   return node.type === 'TemplateLiteral'
 }
 
-class UnsupportedValueError extends Error {}
-class NoSuchDeclarationError extends Error {}
+export class UnsupportedValueError extends Error {}
+export class NoSuchDeclarationError extends Error {}
 
 function extractValue(node: Node): any {
   if (isNullLiteral(node)) {
diff --git a/packages/next/build/analysis/get-page-static-info.ts b/packages/next/build/analysis/get-page-static-info.ts
index 60d94aa800e3..7d2c4d73dbd7 100644
--- a/packages/next/build/analysis/get-page-static-info.ts
+++ b/packages/next/build/analysis/get-page-static-info.ts
@@ -1,6 +1,9 @@
 import { isServerRuntime, ServerRuntime } from '../../server/config-shared'
 import type { NextConfig } from '../../server/config-shared'
-import { tryToExtractExportedConstValue } from './extract-const-value'
+import {
+  extractExportedConstValue,
+  UnsupportedValueError,
+} from './extract-const-value'
 import { escapeStringRegexp } from '../../shared/lib/escape-regexp'
 import { parseModule } from './parse-module'
 import { promises as fs } from 'fs'
@@ -32,13 +35,28 @@ export async function getPageStaticInfo(params: {
   isDev?: boolean
   page?: string
 }): Promise<PageStaticInfo> {
-  const { isDev, pageFilePath, nextConfig } = params
+  const { isDev, pageFilePath, nextConfig, page } = params
 
   const fileContent = (await tryToReadFile(pageFilePath, !isDev)) || ''
   if (/runtime|getStaticProps|getServerSideProps|matcher/.test(fileContent)) {
     const swcAST = await parseModule(pageFilePath, fileContent)
     const { ssg, ssr } = checkExports(swcAST)
-    const config = tryToExtractExportedConstValue(swcAST, 'config') || {}
+
+    // default / failsafe value for config
+    let config: any = {}
+    try {
+      config = extractExportedConstValue(swcAST, 'config')
+    } catch (e) {
+      if (e instanceof UnsupportedValueError) {
+        // `export config` is found, but can't extract its value
+        Log.warn(
+          `You have exported a \`config\` field in "${
+            page || pageFilePath
+          }" that Next.js can't recognize, so it will be ignored`
+        )
+      }
+      // `export config` doesn't exist, or other unknown error throw by swc, silence them
+    }
 
     if (
       typeof config.runtime !== 'string' &&