feat(remix-dev): add warning for v2 "cjs"->"esm" defaults (#6154)

remix-run · Apr 24, 2023 · 8a74add · 8a74add
1 parent 3709710
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diff --git a/.changeset/cjs-esm-warning.md b/.changeset/cjs-esm-warning.md
@@ -0,0 +1,5 @@
+---
+"@remix-run/dev": patch
+---
+
+add warning for v2 "cjs"->"esm" serverModuleFormat default change
diff --git a/docs/pages/v2.md b/docs/pages/v2.md
@@ -689,6 +689,12 @@ module.exports = {
 };
 ```
 
+## `serverModuleFormat`
+
+The default server module output format will be changing from `cjs` to `esm`.
+
+In your `remix.config.js`, you should specify either `serverModuleFormat: "cjs"` to retain existing behavior, or `serverModuleFormat: "esm"`, to opt into the future behavior.
+
 ## Dev Server
 
 We are still stabilizing the new dev server that enables HMR, several CSS libraries (CSS Modules, Vanilla Extract, Tailwind, PostCSS) and simplifies integration with various servers.

diff --git a/integration/hmr-test.ts b/integration/hmr-test.ts
@@ -17,6 +17,7 @@ let fixture = (options: {
   files: {
     "remix.config.js": js`
       module.exports = {
+        serverModuleFormat: "cjs",
         tailwind: true,
         future: {
           unstable_dev: {

diff --git a/packages/remix-dev/__tests__/create-test.ts b/packages/remix-dev/__tests__/create-test.ts
@@ -13,6 +13,7 @@ import {
   flatRoutesWarning,
   formMethodWarning,
   metaWarning,
+  serverModuleFormatWarning,
 } from "../config";
 
 beforeAll(() => server.listen({ onUnhandledRequest: "error" }));
@@ -359,6 +360,8 @@ describe("the create command", () => {
         "\n" +
         metaWarning +
         "\n" +
+        serverModuleFormatWarning +
+        "\n" +
         flatRoutesWarning +
         "\n\n" +
         getOptOutOfInstallMessage() +

diff --git a/packages/remix-dev/config.ts b/packages/remix-dev/config.ts
@@ -455,6 +455,11 @@ export async function readConfig(
   let serverEntryPoint = appConfig.server;
   let serverMainFields = appConfig.serverMainFields;
   let serverMinify = appConfig.serverMinify;
+
+  if (!appConfig.serverModuleFormat) {
+    warnOnce(serverModuleFormatWarning, "serverModuleFormatWarning")
+  }
+
   let serverModuleFormat = appConfig.serverModuleFormat || "cjs";
   let serverPlatform = appConfig.serverPlatform || "node";
   if (isCloudflareRuntime) {
@@ -895,6 +900,12 @@ export let serverBuildTargetWarning =
   "For instructions on making this change see " +
   "https://remix.run/docs/en/v1.15.0/pages/v2#serverbuildtarget";
 
+export const serverModuleFormatWarning =
+  "⚠️ REMIX FUTURE CHANGE: The `serverModuleFormat` config default option will be changing in v2 " +
+  "from `cjs` to `esm`. You can prepare for this change by explicitly specifying `serverModuleFormat: 'cjs'`. " +
+  "For instructions on making this change see " +
+  "https://remix.run/docs/en/v1.16.0/pages/v2#servermoduleformat";
+
 export let flatRoutesWarning =
   "⚠️ REMIX FUTURE CHANGE: The route file convention is changing in v2. " +
   "You can prepare for this change at your convenience with the `v2_routeConvention` future flag. " +