use wrangler aliases for fs calls

Author: dario-piotrowicz

apps/site/.cloudflare/server-only.mjs

@@ -0,0 +1,4 @@
+// In our aliased fs code: apps/site/.cloudflare/node/fs/promises.mjs we are importing `getCloudflareContext`
+// from `@opennextjs/cloudflare`, this in turn imports from `server-only`, this aliasing maxes it so that
+// server-only is not actually removed from the final bundle as it should causing an incorrect server internal
+// error, so here we're also mocking out the server-only module as well

apps/site/CLOUDFLARE.md

@@ -77,7 +77,7 @@ The following is an incomplete list of tasks and problems that still need to be
   - [ ] we need to ensure that we don't end up accidentally downloading this big file to the client as part of hydration
   - [x] once we have easy access to the list of files, we should roll back changes to `next-data/providers/blogData.ts`
 - [ ] back out most changes from `next.dynamic.mjs`
-  - [ ] instead of using runtime detection via `globalThis.navigator?.userAgent`, we should instead use `alias` feature in `wrangler.toml` to override the implementation of `node:fs` calls but only when running in workerd as we need the build to keep on running in node.js for SSG to work
+  - [x] instead of using runtime detection via `globalThis.navigator?.userAgent`, we should instead use `alias` feature in `wrangler.toml` to override the implementation of `node:fs` calls but only when running in workerd as we need the build to keep on running in node.js for SSG to work
   - [ ] could we reimplement the `existsAsync` call as sync `exists` which consults `getMarkdownFiles` from the task above? alternatively
   - [ ] properly implement the rest of `.cloudflare/node/*` polyfills
 - [ ] remove symlink hack in `package.json#build:cloudflare`

apps/site/next.dynamic.mjs

@@ -1,15 +1,13 @@
 'use strict';
 
-import { exists as nodeExists } from 'node:fs';
-import { readFile as nodeReadFile } from 'node:fs/promises';
+import { exists } from 'node:fs';
+import { readFile } from 'node:fs/promises';
 import { join, normalize, sep } from 'node:path';
 
 import matter from 'gray-matter';
 import { cache } from 'react';
 import { VFile } from 'vfile';
 
-import { readFile as runtimeReadFile } from './.cloudflare/node/fs/promises.mjs';
-import { exists as runtimeExists } from './.cloudflare/node/fs.mjs';
 import { getMarkdownFiles } from './.next.helpers.mjs';
 import { BASE_URL, BASE_PATH, IS_DEVELOPMENT } from './next.constants.mjs';
 import {
@@ -21,15 +19,6 @@ import { siteConfig } from './next.json.mjs';
 import { availableLocaleCodes, defaultLocale } from './next.locales.mjs';
 import { compileMDX } from './next.mdx.compiler.mjs';
 
-const readFile =
-  globalThis.navigator?.userAgent === 'Cloudflare-Workers'
-    ? runtimeReadFile
-    : nodeReadFile;
-const exists =
-  globalThis.navigator?.userAgent === 'Cloudflare-Workers'
-    ? runtimeExists
-    : nodeExists;
-
 // This is the combination of the Application Base URL and Base PATH
 const baseUrlAndPath = `${BASE_URL}${BASE_PATH}`;
 
@@ -50,7 +39,7 @@ const createCachedMarkdownCache = () => {
   if (IS_DEVELOPMENT) {
     return {
       has: () => false,
-      set: () => {},
+      set: () => { },
       get: () => null,
     };
   }

apps/site/wrangler.toml

@@ -9,11 +9,9 @@ enabled = true
 head_sampling_rate = 1
 
 [alias]
-# "node:fs" = "./.cloudflare/node/fs.mjs"
-# "node:fs/promises" = "./.cloudflare/node/fs/promises.mjs"
-# "node:fs" = "./.cloudflare/node/fs.mjs"
-# "node:fs/promises" = "./.cloudflare/node/fs/promises.mjs"
-
+"node:fs" = "./.cloudflare/node/fs.mjs"
+"node:fs/promises" = "./.cloudflare/node/fs/promises.mjs"
+"server-only" = "./.cloudflare/server-only.mjs"
 
 [assets]
 directory = ".open-next/assets"