feat(vercel): allow overriding function config by route

src/presets/vercel/types.ts

@@ -147,6 +147,24 @@ export interface VercelOptions {
    * @see https://vercel.com/docs/cron-jobs
    */
   cronHandlerRoute?: string;
+
+  /**
+   * Per-route function configuration overrides.
+   *
+   * Keys are route patterns (e.g., `/api/queues/*`, `/api/slow-routes/**`).
+   * Values are partial {@link VercelServerlessFunctionConfig} objects.
+   *
+   * @example
+   * ```ts
+   * routeFunctionConfig: {
+   *   '/api/my-slow-routes/**': { maxDuration: 3600 },
+   *   '/api/queues/fulfill-order': {
+   *     experimentalTriggers: [{ type: 'queue/v2beta', topic: 'orders' }],
+   *   },
+   * }
+   * ```
+   */
+  routeFunctionConfig?: Record<string, VercelServerlessFunctionConfig>;
 }
 
 /**

src/presets/vercel/utils.ts

@@ -3,6 +3,7 @@ import { defu } from "defu";
 import { writeFile } from "../_utils/fs.ts";
 import type { Nitro, NitroRouteRules } from "nitro/types";
 import { dirname, relative, resolve } from "pathe";
+import { createRouter, addRoute, findRoute } from "rou3";
 import { joinURL, withLeadingSlash, withoutLeadingSlash } from "ufo";
 import type {
   PrerenderFunctionConfig,
@@ -48,15 +49,26 @@ export async function generateFunctionFiles(nitro: Nitro) {
   const buildConfig = generateBuildConfig(nitro, o11Routes);
   await writeFile(buildConfigPath, JSON.stringify(buildConfig, null, 2));
 
-  const functionConfigPath = resolve(nitro.options.output.serverDir, ".vc-config.json");
-  const functionConfig: VercelServerlessFunctionConfig = {
+  const baseFunctionConfig: VercelServerlessFunctionConfig = {
     handler: "index.mjs",
     launcherType: "Nodejs",
     shouldAddHelpers: false,
     supportsResponseStreaming: true,
     ...nitro.options.vercel?.functions,
   };
-  await writeFile(functionConfigPath, JSON.stringify(functionConfig, null, 2));
+  const functionConfigPath = resolve(nitro.options.output.serverDir, ".vc-config.json");
+  await writeFile(functionConfigPath, JSON.stringify(baseFunctionConfig, null, 2));
+
+  // Build rou3 router for routeFunctionConfig matching
+  const routeFunctionConfig = nitro.options.vercel?.routeFunctionConfig;
+  const hasRouteFunctionConfig = routeFunctionConfig && Object.keys(routeFunctionConfig).length > 0;
+  let routeFuncRouter: ReturnType<typeof createRouter<VercelServerlessFunctionConfig>> | undefined;
+  if (hasRouteFunctionConfig) {
+    routeFuncRouter = createRouter<VercelServerlessFunctionConfig>();
+    for (const [pattern, overrides] of Object.entries(routeFunctionConfig)) {
+      addRoute(routeFuncRouter, "", pattern, overrides);
+    }
+  }
 
   // Write ISR functions
   for (const [key, value] of Object.entries(nitro.options.routeRules)) {
@@ -70,18 +82,49 @@ export async function generateFunctionFiles(nitro: Nitro) {
       normalizeRouteDest(key) + ISR_SUFFIX
     );
     await fsp.mkdir(dirname(funcPrefix), { recursive: true });
-    await fsp.symlink(
-      "./" + relative(dirname(funcPrefix), nitro.options.output.serverDir),
-      funcPrefix + ".func",
-      "junction"
-    );
+
+    const match = routeFuncRouter && findRoute(routeFuncRouter, "", key);
+    if (match) {
+      await createFunctionDirWithCustomConfig(
+        funcPrefix + ".func",
+        nitro.options.output.serverDir,
+        baseFunctionConfig,
+        match.data
+      );
+    } else {
+      await fsp.symlink(
+        "./" + relative(dirname(funcPrefix), nitro.options.output.serverDir),
+        funcPrefix + ".func",
+        "junction"
+      );
+    }
+
     await writePrerenderConfig(
       funcPrefix + ".prerender-config.json",
       value.isr,
       nitro.options.vercel?.config?.bypassToken
     );
   }
 
+  // Write routeFunctionConfig custom function directories
+  const createdFuncDirs = new Set<string>();
+  if (hasRouteFunctionConfig) {
+    for (const [pattern, overrides] of Object.entries(routeFunctionConfig!)) {
+      const funcDir = resolve(
+        nitro.options.output.serverDir,
+        "..",
+        normalizeRouteDest(pattern) + ".func"
+      );
+      await createFunctionDirWithCustomConfig(
+        funcDir,
+        nitro.options.output.serverDir,
+        baseFunctionConfig,
+        overrides
+      );
+      createdFuncDirs.add(funcDir);
+    }
+  }
+
   // Write observability routes
   if (o11Routes.length === 0) {
     return;
@@ -94,12 +137,29 @@ export async function generateFunctionFiles(nitro: Nitro) {
       continue; // #3563
     }
     const funcPrefix = resolve(nitro.options.output.serverDir, "..", route.dest);
-    await fsp.mkdir(dirname(funcPrefix), { recursive: true });
-    await fsp.symlink(
-      "./" + relative(dirname(funcPrefix), nitro.options.output.serverDir),
-      funcPrefix + ".func",
-      "junction"
-    );
+    const funcDir = funcPrefix + ".func";
+
+    // Skip if already created by routeFunctionConfig
+    if (createdFuncDirs.has(funcDir)) {
+      continue;
+    }
+
+    const match = routeFuncRouter && findRoute(routeFuncRouter, "", route.src);
+    if (match) {
+      await createFunctionDirWithCustomConfig(
+        funcDir,
+        nitro.options.output.serverDir,
+        baseFunctionConfig,
+        match.data
+      );
+    } else {
+      await fsp.mkdir(dirname(funcPrefix), { recursive: true });
+      await fsp.symlink(
+        "./" + relative(dirname(funcPrefix), nitro.options.output.serverDir),
+        funcDir,
+        "junction"
+      );
+    }
   }
 }
 
@@ -273,6 +333,13 @@ function generateBuildConfig(nitro: Nitro, o11Routes?: ObservabilityRoute[]) {
           ),
         };
       }),
+    // Route function config routes
+    ...(nitro.options.vercel?.routeFunctionConfig
+      ? Object.keys(nitro.options.vercel.routeFunctionConfig).map((pattern) => ({
+          src: normalizeRouteSrc(pattern),
+          dest: withLeadingSlash(normalizeRouteDest(pattern)),
+        }))
+      : []),
     // Observability routes
     ...(o11Routes || []).map((route) => ({
       src: joinURL(nitro.options.baseURL, route.src),
@@ -512,6 +579,25 @@ function normalizeRouteDest(route: string) {
   );
 }
 
+async function createFunctionDirWithCustomConfig(
+  funcDir: string,
+  serverDir: string,
+  baseFunctionConfig: VercelServerlessFunctionConfig,
+  overrides: VercelServerlessFunctionConfig
+) {
+  await fsp.mkdir(funcDir, { recursive: true });
+  const entries = await fsp.readdir(serverDir);
+  for (const entry of entries) {
+    if (entry === ".vc-config.json") {
+      continue;
+    }
+    const target = "./" + relative(funcDir, resolve(serverDir, entry));
+    await fsp.symlink(target, resolve(funcDir, entry), "junction");
+  }
+  const mergedConfig = defu(overrides, baseFunctionConfig);
+  await writeFile(resolve(funcDir, ".vc-config.json"), JSON.stringify(mergedConfig, null, 2));
+}
+
 async function writePrerenderConfig(
   filename: string,
   isrConfig: NitroRouteRules["isr"],

test/presets/vercel.test.ts

@@ -531,6 +531,78 @@ describe("nitro:preset:vercel:bun", async () => {
   });
 });
 
+describe("nitro:preset:vercel:route-function-config", async () => {
+  const ctx = await setupTest("vercel", {
+    outDirSuffix: "-route-func-config",
+    config: {
+      preset: "vercel",
+      vercel: {
+        routeFunctionConfig: {
+          "/api/hello": {
+            maxDuration: 300,
+          },
+          "/api/echo": {
+            experimentalTriggers: [{ type: "queue/v2beta", topic: "orders" }],
+          },
+        },
+      },
+    },
+  });
+
+  it("should create custom function directory (not symlink)", async () => {
+    const funcDir = resolve(ctx.outDir, "functions/api/hello.func");
+    const stat = await fsp.lstat(funcDir);
+    expect(stat.isDirectory()).toBe(true);
+    expect(stat.isSymbolicLink()).toBe(false);
+  });
+
+  it("should write merged .vc-config.json with overrides", async () => {
+    const config = await fsp
+      .readFile(resolve(ctx.outDir, "functions/api/hello.func/.vc-config.json"), "utf8")
+      .then((r) => JSON.parse(r));
+    expect(config.maxDuration).toBe(300);
+    expect(config.handler).toBe("index.mjs");
+    expect(config.launcherType).toBe("Nodejs");
+    expect(config.supportsResponseStreaming).toBe(true);
+  });
+
+  it("should write custom config with arbitrary fields", async () => {
+    const config = await fsp
+      .readFile(resolve(ctx.outDir, "functions/api/echo.func/.vc-config.json"), "utf8")
+      .then((r) => JSON.parse(r));
+    expect(config.experimentalTriggers).toEqual([{ type: "queue/v2beta", topic: "orders" }]);
+    expect(config.handler).toBe("index.mjs");
+  });
+
+  it("should symlink files inside custom function directory to __server.func", async () => {
+    const funcDir = resolve(ctx.outDir, "functions/api/hello.func");
+    const entries = await fsp.readdir(funcDir, { withFileTypes: true });
+    const indexEntry = entries.find((e) => e.name === "index.mjs");
+    expect(indexEntry).toBeDefined();
+    const indexStat = await fsp.lstat(resolve(funcDir, "index.mjs"));
+    expect(indexStat.isSymbolicLink()).toBe(true);
+  });
+
+  it("should add routing entries for custom function routes in config.json", async () => {
+    const config = await fsp
+      .readFile(resolve(ctx.outDir, "config.json"), "utf8")
+      .then((r) => JSON.parse(r));
+    const routes = config.routes as { src: string; dest: string }[];
+    const helloRoute = routes.find((r) => r.dest === "/api/hello" && r.src === "/api/hello");
+    expect(helloRoute).toBeDefined();
+    const echoRoute = routes.find((r) => r.dest === "/api/echo" && r.src === "/api/echo");
+    expect(echoRoute).toBeDefined();
+  });
+
+  it("should keep base __server.func with standard config", async () => {
+    const config = await fsp
+      .readFile(resolve(ctx.outDir, "functions/__server.func/.vc-config.json"), "utf8")
+      .then((r) => JSON.parse(r));
+    expect(config.maxDuration).toBeUndefined();
+    expect(config.handler).toBe("index.mjs");
+  });
+});
+
 describe.skip("nitro:preset:vercel:bun-verceljson", async () => {
   const vercelJsonPath = join(fixtureDir, "vercel.json");