add support for additional Next.js config file types

CHANGELOG.md

@@ -0,0 +1 @@
+- add support for `next.config.ts` and `next.config.mts` in Next.js deployments (#9871)

src/frameworks/next/constants.ts

@@ -23,7 +23,12 @@ export const APP_PATHS_MANIFEST: typeof APP_PATHS_MANIFEST_TYPE = "app-paths-man
 export const SERVER_REFERENCE_MANIFEST: `${typeof SERVER_REFERENCE_MANIFEST_TYPE}.json` =
   "server-reference-manifest.json";
 
-export const CONFIG_FILES = ["next.config.js", "next.config.mjs"] as const;
+export const CONFIG_FILES = [
+  "next.config.js",
+  "next.config.mjs",
+  "next.config.ts",
+  "next.config.mts",
+] as const;
 
 export const ESBUILD_VERSION = "^0.19.2";
 

src/frameworks/next/index.ts

@@ -100,13 +100,13 @@
 const DEFAULT_NUMBER_OF_REASONS_TO_LIST = 5;
 
 function getReactVersion(cwd: string): string | undefined {
   return findDependency("react-dom", { cwd, omitDev: false })?.version;
 }
 
 /**
  * Returns whether this codebase is a Next.js backend.
  */
 export async function discover(dir: string) {
   if (!(await pathExists(join(dir, "package.json")))) return;
   const version = getNextVersion(dir);
   if (!(await whichNextConfigFile(dir)) && !version) return;
@@ -163,10 +163,10 @@
 
   const nextBuild = new Promise((resolve, reject) => {
     const buildProcess = spawn(cli, ["build"], { cwd: dir, env });
     buildProcess.stdout?.on("data", (data) => logger.info(data.toString()));
     buildProcess.stderr?.on("data", (data) => logger.info(data.toString()));
     buildProcess.on("error", (err) => {
       reject(new FirebaseError(`Unable to build your Next.js app: ${err}`));
     });
     buildProcess.on("exit", (code) => {
       resolve(code);
@@ -684,9 +684,12 @@
         logLevel: "error",
         external: productionDeps,
       };
-      if (configFile === "next.config.mjs") {
-        // ensure generated file is .mjs if the config is .mjs
+      if (configFile === "next.config.mjs" || configFile === "next.config.mts") {
+        // ensure generated file is .mjs if the config is .mjs or .mts
         esbuildArgs.format = "esm";
+        esbuildArgs.outfile = join(destDir, "next.config.mjs");
+      } else {
+        esbuildArgs.outfile = join(destDir, "next.config.js");
       }
 
       const bundle = await esbuild.build(esbuildArgs);

src/frameworks/next/utils.spec.ts

@@ -40,6 +40,7 @@ import {
   findEsbuildPath,
   installEsbuild,
   isNextJsVersionVulnerable,
+  whichNextConfigFile,
 } from "./utils";
 
 import * as frameworksUtils from "../utils";
@@ -76,6 +77,62 @@ import {
 import { pathsWithCustomRoutesInternalPrefix } from "./testing/i18n";
 
 describe("Next.js utils", () => {
+  describe("whichNextConfigFile", () => {
+    let sandbox: sinon.SinonSandbox;
+    let pathExistsStub: sinon.SinonStub;
+
+    beforeEach(() => {
+      sandbox = sinon.createSandbox();
+      pathExistsStub = sandbox.stub(fsExtra, "pathExists");
+    });
+
+    afterEach(() => {
+      sandbox.restore();
+    });
+
+    it("should return next.config.js if it exists", async () => {
+      pathExistsStub.withArgs("next.config.js").resolves(true);
+      pathExistsStub.resolves(false);
+
+      expect(await whichNextConfigFile("")).to.equal("next.config.js");
+    });
+
+    it("should return next.config.mjs if it exists", async () => {
+      pathExistsStub.withArgs("next.config.mjs").resolves(true);
+      pathExistsStub.resolves(false);
+
+      expect(await whichNextConfigFile("")).to.equal("next.config.mjs");
+    });
+
+    it("should return next.config.ts if it exists", async () => {
+      pathExistsStub.withArgs("next.config.ts").resolves(true);
+      pathExistsStub.resolves(false);
+
+      expect(await whichNextConfigFile("")).to.equal("next.config.ts");
+    });
+
+    it("should return next.config.mts if it exists", async () => {
+      pathExistsStub.withArgs("next.config.mts").resolves(true);
+      pathExistsStub.resolves(false);
+
+      expect(await whichNextConfigFile("")).to.equal("next.config.mts");
+    });
+
+    it("should return null if no config file exists", async () => {
+      pathExistsStub.resolves(false);
+
+      expect(await whichNextConfigFile("")).to.be.null;
+    });
+
+    it("should prioritize next.config.js over others", async () => {
+      pathExistsStub.withArgs("next.config.js").resolves(true);
+      pathExistsStub.withArgs("next.config.mjs").resolves(true);
+      pathExistsStub.resolves(false);
+
+      expect(await whichNextConfigFile("")).to.equal("next.config.js");
+    });
+  });
+
   describe("cleanEscapedChars", () => {
     it("should clean escaped chars", () => {
       // path containing all escaped chars