Fix custom cache handler importing on windows (#60312)

### Fixing a bug

### What?
Custom cache handler doesn't work on Windows

### Why?

It broke in a recent fix, when adding ESM support - #59863. The problem
is not new - dynamic imports consider an absolute path in Windows as a
protocol:

`ERR! Error [ERR_UNSUPPORTED_ESM_URL_SCHEME]: Only URLs with a scheme
in: file, data are supported by the default ESM loader. On Windows,
absolute paths must be valid file:// URLs. Received protocol 'C:'`

### How?

As a solution, it is necessary to explicitly indicate that it is indeed
an absolute path, for example by adding a / at the beginning, but the
most reliable way is to use pathToFileURL.

Since the logic is repeated in 4 places - I created a common function.

Fixes #58509

---------

Co-authored-by: JJ Kasper <jj@jjsweb.site>

packages/next/src/build/index.ts

@@ -163,6 +163,7 @@ import { getStartServerInfo, logStartInfo } from '../server/lib/app-info-log'
 import type { NextEnabledDirectories } from '../server/base-server'
 import { hasCustomExportOutput } from '../export/utils'
 import { interopDefault } from '../lib/interop-default'
+import { formatDynamicImportPath } from '../lib/format-dynamic-import-path'
 
 interface ExperimentalBypassForInfo {
   experimentalBypassFor?: RouteHas[]
@@ -1537,10 +1538,8 @@ export default async function build(
         if (incrementalCacheHandlerPath) {
           CacheHandler = interopDefault(
             await import(
-              path.isAbsolute(incrementalCacheHandlerPath)
-                ? incrementalCacheHandlerPath
-                : path.join(dir, incrementalCacheHandlerPath)
-            )
+              formatDynamicImportPath(dir, incrementalCacheHandlerPath)
+            ).then((mod) => mod.default || mod)
           )
         }
 

packages/next/src/build/utils.ts

@@ -82,6 +82,7 @@ import { RouteKind } from '../server/future/route-kind'
 import { isAppRouteRouteModule } from '../server/future/route-modules/checks'
 import { interopDefault } from '../lib/interop-default'
 import type { PageExtensions } from './page-extensions-type'
+import { formatDynamicImportPath } from '../lib/format-dynamic-import-path'
 
 export type ROUTER_TYPE = 'pages' | 'app'
 
@@ -1314,10 +1315,8 @@ export async function buildAppStaticPaths({
   if (incrementalCacheHandlerPath) {
     CacheHandler = interopDefault(
       await import(
-        path.isAbsolute(incrementalCacheHandlerPath)
-          ? incrementalCacheHandlerPath
-          : path.join(dir, incrementalCacheHandlerPath)
-      )
+        formatDynamicImportPath(dir, incrementalCacheHandlerPath)
+      ).then((mod) => mod.default || mod)
     )
   }
 

packages/next/src/export/helpers/create-incremental-cache.ts

@@ -5,6 +5,7 @@ import { IncrementalCache } from '../../server/lib/incremental-cache'
 import { hasNextSupport } from '../../telemetry/ci-info'
 import { nodeFs } from '../../server/lib/node-fs-methods'
 import { interopDefault } from '../../lib/interop-default'
+import { formatDynamicImportPath } from '../../lib/format-dynamic-import-path'
 
 export async function createIncrementalCache({
   incrementalCacheHandlerPath,
@@ -29,13 +30,9 @@ export async function createIncrementalCache({
   let CacheHandler: any
   if (incrementalCacheHandlerPath) {
     CacheHandler = interopDefault(
-      (
-        await import(
-          path.isAbsolute(incrementalCacheHandlerPath)
-            ? incrementalCacheHandlerPath
-            : path.join(dir, incrementalCacheHandlerPath)
-        )
-      ).default
+      await import(
+        formatDynamicImportPath(dir, incrementalCacheHandlerPath)
+      ).then((mod) => mod.default || mod)
     )
   }
 

packages/next/src/lib/format-dynamic-import-path.ts

@@ -0,0 +1,19 @@
+import path from 'path'
+import { pathToFileURL } from 'url'
+
+/**
+ * The path for a dynamic route must be URLs with a valid scheme.
+ *
+ * When an absolute Windows path is passed to it, it interprets the beginning of the path as a protocol (`C:`).
+ * Therefore, it is important to always construct a complete path.
+ * @param dir File directory
+ * @param filePath Absolute or relative path
+ */
+export const formatDynamicImportPath = (dir: string, filePath: string) => {
+  const absoluteFilePath = path.isAbsolute(filePath)
+    ? filePath
+    : path.join(dir, filePath)
+  const formattedFilePath = pathToFileURL(absoluteFilePath).toString()
+
+  return formattedFilePath
+}

packages/next/src/server/next-server.ts

@@ -26,7 +26,7 @@ import type { ParsedUrl } from '../shared/lib/router/utils/parse-url'
 import type { Revalidate } from './lib/revalidate'
 
 import fs from 'fs'
-import { join, resolve, isAbsolute } from 'path'
+import { join, resolve } from 'path'
 import { getRouteMatcher } from '../shared/lib/router/utils/route-matcher'
 import { addRequestMeta, getRequestMeta } from './request-meta'
 import {
@@ -101,6 +101,7 @@ import { loadManifest } from './load-manifest'
 import { lazyRenderAppPage } from './future/route-modules/app-page/module.render'
 import { lazyRenderPagesPage } from './future/route-modules/pages/module.render'
 import { interopDefault } from '../lib/interop-default'
+import { formatDynamicImportPath } from '../lib/format-dynamic-import-path'
 
 export * from './base-server'
 
@@ -108,8 +109,9 @@ declare const __non_webpack_require__: NodeRequire
 
 // For module that can be both CJS or ESM
 const dynamicImportEsmDefault = process.env.NEXT_MINIMAL
-  ? __non_webpack_require__
-  : async (mod: string) => (await import(mod)).default
+  ? (id: string) =>
+      import(/* webpackIgnore: true */ id).then((mod) => mod.default || mod)
+  : (id: string) => import(id).then((mod) => mod.default || mod)
 
 // For module that will be compiled to CJS, e.g. instrument
 const dynamicRequire = process.env.NEXT_MINIMAL
@@ -310,9 +312,7 @@ export default class NextNodeServer extends BaseServer {
     if (incrementalCacheHandlerPath) {
       CacheHandler = interopDefault(
         await dynamicImportEsmDefault(
-          isAbsolute(incrementalCacheHandlerPath)
-            ? incrementalCacheHandlerPath
-            : join(this.distDir, incrementalCacheHandlerPath)
+          formatDynamicImportPath(this.distDir, incrementalCacheHandlerPath)
         )
       )
     }