fix(@astrojs/vercel): slowness and symbolic link

.changeset/proud-forks-rescue.md

@@ -0,0 +1,6 @@
+---
+'@astrojs/vercel': patch
+---
+
+- Cache result during bundling, to speed up the process of multiple functions;
+- Avoid creating multiple symbolic links of the dependencies when building the project with `funcitonPerRoute` enabled;

packages/integrations/vercel/src/lib/fs.ts

@@ -1,5 +1,6 @@
 import type { PathLike } from 'node:fs';
 import * as fs from 'node:fs/promises';
+import { existsSync } from 'node:fs';
 import nodePath from 'node:path';
 import { fileURLToPath } from 'node:url';
 
@@ -74,11 +75,13 @@ export async function copyFilesToFunction(
 
 		if (isSymlink) {
 			const realdest = fileURLToPath(new URL(nodePath.relative(commonAncestor, realpath), outDir));
-			await fs.symlink(
-				nodePath.relative(fileURLToPath(new URL('.', dest)), realdest),
-				dest,
-				isDir ? 'dir' : 'file'
-			);
+			const target = nodePath.relative(fileURLToPath(new URL('.', dest)), realdest);
+			// NOTE: when building function per route, dependencies are linked at the first run, then there's no need anymore to do that once more.
+			// So we check if the destination already exists. If it does, move on.
+			// Symbolic links here are usually dependencies and not user code. Symbolic links exist because of the pnpm strategy.
+			if (!existsSync(dest)) {
+				await fs.symlink(target, dest, isDir ? 'dir' : 'file');
+			}
 		} else if (!isDir) {
 			await fs.copyFile(origin, dest);
 		}

packages/integrations/vercel/src/lib/nft.ts

@@ -1,19 +1,28 @@
 import { relative as relativePath } from 'node:path';
 import { fileURLToPath } from 'node:url';
+import { relative } from 'node:path';
 import { copyFilesToFunction } from './fs.js';
+import type { AstroIntegrationLogger } from 'astro';
 
-export async function copyDependenciesToFunction({
-	entry,
-	outDir,
-	includeFiles,
-	excludeFiles,
-}: {
-	entry: URL;
-	outDir: URL;
-	includeFiles: URL[];
-	excludeFiles: URL[];
-}): Promise<{ handler: string }> {
+export async function copyDependenciesToFunction(
+	{
+		entry,
+		outDir,
+		includeFiles,
+		excludeFiles,
+		logger,
+	}: {
+		entry: URL;
+		outDir: URL;
+		includeFiles: URL[];
+		excludeFiles: URL[];
+		logger: AstroIntegrationLogger;
+	},
+	// we want to pass the caching by reference, and not by value
+	cache: object
+): Promise<{ handler: string }> {
 	const entryPath = fileURLToPath(entry);
+	logger.info(`Bundling function ${relative(fileURLToPath(outDir), entryPath)}`);
 
 	// Get root of folder of the system (like C:\ on Windows or / on Linux)
 	let base = entry;
@@ -31,6 +40,7 @@ export async function copyDependenciesToFunction({
 		// If you have a route of /dev this appears in source and NFT will try to
 		// scan your local /dev :8
 		ignore: ['/dev/**'],
+		cache,
 	});
 
 	for (const error of result.warnings) {

packages/integrations/vercel/src/serverless/adapter.ts

@@ -1,4 +1,10 @@
-import type { AstroAdapter, AstroConfig, AstroIntegration, RouteData } from 'astro';
+import type {
+	AstroAdapter,
+	AstroConfig,
+	AstroIntegration,
+	RouteData,
+	AstroIntegrationLogger,
+} from 'astro';
 import { AstroError } from 'astro/errors';
 import glob from 'fast-glob';
 import { basename } from 'node:path';
@@ -78,16 +84,27 @@ export default function vercelServerless({
 	// Extra files to be merged with `includeFiles` during build
 	const extraFilesToInclude: URL[] = [];
 
-	async function createFunctionFolder(funcName: string, entry: URL, inc: URL[]) {
+	const NTF_CACHE = Object.create(null);
+
+	async function createFunctionFolder(
+		funcName: string,
+		entry: URL,
+		inc: URL[],
+		logger: AstroIntegrationLogger
+	) {
 		const functionFolder = new URL(`./functions/${funcName}.func/`, _config.outDir);
 
 		// Copy necessary files (e.g. node_modules/)
-		const { handler } = await copyDependenciesToFunction({
-			entry,
-			outDir: functionFolder,
-			includeFiles: inc,
-			excludeFiles: excludeFiles?.map((file) => new URL(file, _config.root)) || [],
-		});
+		const { handler } = await copyDependenciesToFunction(
+			{
+				entry,
+				outDir: functionFolder,
+				includeFiles: inc,
+				excludeFiles: excludeFiles?.map((file) => new URL(file, _config.root)) || [],
+				logger,
+			},
+			NTF_CACHE
+		);
 
 		// Enable ESM
 		// https://aws.amazon.com/blogs/compute/using-node-js-es-modules-and-top-level-await-in-aws-lambda/
@@ -167,7 +184,7 @@ You can set functionPerRoute: false to prevent surpassing the limit.`
 				}
 			},
 
-			'astro:build:done': async ({ routes }) => {
+			'astro:build:done': async ({ routes, logger }) => {
 				// Merge any includes from `vite.assetsInclude
 				if (_config.vite.assetsInclude) {
 					const mergeGlobbedIncludes = (globPattern: unknown) => {
@@ -192,7 +209,7 @@ You can set functionPerRoute: false to prevent surpassing the limit.`
 				if (_entryPoints.size) {
 					for (const [route, entryFile] of _entryPoints) {
 						const func = basename(entryFile.toString()).replace(/\.mjs$/, '');
-						await createFunctionFolder(func, entryFile, filesToInclude);
+						await createFunctionFolder(func, entryFile, filesToInclude, logger);
 						routeDefinitions.push({
 							src: route.pattern.source,
 							dest: func,
@@ -202,7 +219,8 @@ You can set functionPerRoute: false to prevent surpassing the limit.`
 					await createFunctionFolder(
 						'render',
 						new URL(serverEntry, buildTempFolder),
-						filesToInclude
+						filesToInclude,
+						logger
 					);
 					routeDefinitions.push({ src: '/.*', dest: 'render' });
 				}