refactor: patch findDir using ast-grep (#392)

Author: vicb

packages/cloudflare/src/cli/build/bundle-server.ts

@@ -12,6 +12,7 @@ import * as patches from "./patches/index.js";
 import { ContentUpdater } from "./patches/plugins/content-updater.js";
 import { inlineEvalManifest } from "./patches/plugins/eval-manifest.js";
 import { patchFetchCacheSetMissingWaitUntil } from "./patches/plugins/fetch-cache-wait-until.js";
+import { inlineFindDir } from "./patches/plugins/find-dir.js";
 import { patchLoadInstrumentation } from "./patches/plugins/load-instrumentation.js";
 import { handleOptionalDependencies } from "./patches/plugins/optional-deps.js";
 import { fixRequire } from "./patches/plugins/require.js";
@@ -91,6 +92,7 @@ export async function bundleServer(buildOpts: BuildOptions): Promise<void> {
       patchLoadInstrumentation(updater),
       patchFetchCacheSetMissingWaitUntil(updater),
       inlineEvalManifest(updater, buildOpts),
+      inlineFindDir(updater, buildOpts),
       // Apply updater updaters, must be the last plugin
       updater.plugin,
     ],
@@ -195,7 +197,6 @@ export async function updateWorkerBundledCode(
     ["require", patches.patchRequire],
     ["`buildId` function", (code) => patches.patchBuildId(code, buildOpts)],
     ["`loadManifest` function", (code) => patches.patchLoadManifest(code, buildOpts)],
-    ["`findDir` function", (code) => patches.patchFindDir(code, buildOpts)],
     ["cacheHandler", (code) => patches.patchCache(code, buildOpts)],
     [
       "'require(this.middlewareManifestPath)'",

packages/cloudflare/src/cli/build/patches/plugins/find-dir.ts

@@ -0,0 +1,50 @@
+/**
+ * Inline `evalManifest` as it relies on `readFileSync` and `runInNewContext`
+ * that are not supported by workerd.
+ */
+
+import { existsSync } from "node:fs";
+import { join } from "node:path";
+
+import { type BuildOptions, getPackagePath } from "@opennextjs/aws/build/helper.js";
+import { getCrossPlatformPathRegex } from "@opennextjs/aws/utils/regex.js";
+
+import { patchCode } from "../ast/util.js";
+import type { ContentUpdater } from "./content-updater.js";
+
+export function inlineFindDir(updater: ContentUpdater, buildOpts: BuildOptions) {
+  return updater.updateContent(
+    "inline-find-dir",
+    {
+      filter: getCrossPlatformPathRegex(String.raw`/next/dist/lib/find-pages-dir\.js$`, { escape: false }),
+      contentFilter: /function findDir\(/,
+    },
+    async ({ contents }) => patchCode(contents, await getRule(buildOpts))
+  );
+}
+
+async function getRule(buildOpts: BuildOptions) {
+  const { outputDir } = buildOpts;
+
+  const baseDir = join(outputDir, "server-functions/default", getPackagePath(buildOpts), ".next/server");
+
+  const appExists = existsSync(join(baseDir, "app"));
+  const pagesExists = existsSync(join(baseDir, "pages"));
+
+  return `
+rule:
+  pattern: function findDir($DIR, $NAME) { $$$_ }
+fix: |-
+  function findDir($DIR, $NAME) {
+    if ($DIR.endsWith(".next/server")) {
+      if ($NAME === "app") {
+        return ${appExists};
+      }
+      if ($NAME === "pages") {
+        return ${pagesExists};
+      }
+    }
+    throw new Error(\`Unexpected findDir(\${$DIR}, \${$NAME}) call!\`);
+  }
+`;
+}

packages/cloudflare/src/cli/build/patches/to-investigate/index.ts

@@ -1,4 +1,3 @@
 export * from "./inline-middleware-manifest-require.js";
 export * from "./patch-exception-bubbling.js";
-export * from "./patch-find-dir.js";
 export * from "./patch-read-file.js";