fix: loader: typescript module resolver not resolving to source path of symlinked module

Author: AlessioGr

packages/payload/src/bin/loader/index.ts

@@ -6,6 +6,7 @@ import { fileURLToPath, pathToFileURL } from 'url'
 
 import { CLIENT_EXTENSIONS } from './clientExtensions.js'
 import { compile } from './compile.js'
+import { resolveOriginalPath } from './resolveOriginalPath.js'
 
 interface ResolveContext {
   conditions: string[]
@@ -115,7 +116,7 @@ export const resolve: ResolveFn = async (specifier, context, nextResolve) => {
     return {
       format: resolvedIsTS ? 'ts' : undefined,
       shortCircuit: true,
-      url: pathToFileURL(resolvedModule.resolvedFileName).href,
+      url: pathToFileURL(await resolveOriginalPath(resolvedModule.resolvedFileName)).href, // The typescript module resolver does not resolve to the original path, but to the symlinked path, if present. This can cause issues
     }
   }
 

packages/payload/src/bin/loader/resolveOriginalPath.ts

@@ -0,0 +1,35 @@
+import fs from 'fs/promises'
+import path from 'path'
+
+/**
+ * In case any directory in the path contains symlinks, this function attempts to detect that resolves the original path.
+ *
+ * Example Input: /Users/alessio/Documents/GitHub/payload-3.0-alpha-demo/node_modules/tailwindcss/resolveConfig.js
+ * The "tailwindcss" in this example is a symlinked directory.
+ *
+ * Example Output: /Users/alessio/Documents/GitHub/payload-3.0-alpha-demo/node_modules/.pnpm/tailwindcss@3.4.3/node_modules/tailwindcss/resolveConfig.js
+ */
+export async function resolveOriginalPath(filePath: string) {
+  try {
+    // Normalize and split the path
+    const parts = path.resolve(filePath).split(path.sep)
+
+    let currentPath = '/'
+    // skip the first slash
+    for (const part of parts.slice(1)) {
+      currentPath = path.join(currentPath, part)
+
+      // Check if the current path component is a symlink
+      const stats = await fs.lstat(currentPath)
+      if (stats.isSymbolicLink()) {
+        // Resolve the symlink
+        const resolvedLink = await fs.readlink(currentPath)
+        currentPath = path.join(path.dirname(currentPath), resolvedLink)
+      }
+    }
+
+    return currentPath
+  } catch (error) {
+    console.error('Error resolving path:', error)
+  }
+}