avoid tweaking _ENTRIES if an _ENTRIES declaration is present (cl…

…oudflare#852)

packages/next-on-pages/src/buildApplication/processVercelFunctions/dedupeEdgeFunctions.ts

@@ -292,15 +292,22 @@ function iifefyFunctionFile(
 	functionInfo: FunctionInfo,
 	chunksExportsMap: Map<string, Set<string>>,
 ): string {
+	const fileContentsContainEntriesDeclaration =
+		/(let|var|const)\s+_ENTRIES\s*=/.test(fileContents);
+
+	// it looks like there can be direct references to _ENTRIES (i.e. `_ENTRIES` instead of `globalThis._ENTRIES` etc...)
+	// we have to update all such references otherwise our proxying won't take effect on those, but only if the file doesn't
+	// actually declare _ENTRIES itself (as it happens in older Vercel CLI version (v31 and older))
+	if (!fileContentsContainEntriesDeclaration) {
+		fileContents = fileContents.replace(
+			/([^.])_ENTRIES/g,
+			'$1globalThis._ENTRIES',
+		);
+	}
+
 	const wrappedContent = `
 		export default ((self, globalThis, global) => {
 			${fileContents
-				// it looks like there can be direct references to _ENTRIES (i.e. `_ENTRIES` instead of `globalThis._ENTRIES` etc...)
-				// we have to update all such references otherwise our proxying won't take effect on those
-				// (note: older versions of the Vercel CLI (v31 and older) used to declare _ENTRIES as "let _ENTRIES = {};", so we do
-				// need to make sure that we don't add `globalThis.` in these cases (if we were to drop support for those older versions
-				// the below line to: ".replace(/([^.])_ENTRIES/g, '$1globalThis._ENTRIES')")
-				.replace(/(?<!(let)\s*)([^.]|^)_ENTRIES/g, '$2globalThis._ENTRIES')
 				// the default export needs to become the return value of the iife, which is then re-exported as default
 				.replace(/export\s+default\s+/g, 'return ')}
 		})(proxy, proxy, proxy);