vite: profiling

build: `--profile`
dev:
  `--profile` to start with profiler
  `p + enter` to write profile and restart profiler

.changeset/twenty-pandas-attend.md

@@ -0,0 +1,10 @@
+---
+"@remix-run/dev": patch
+---
+
+vite: profiling
+
+- build: `--profile`
+- dev:
+  - `--profile` to start with profiler
+  - `p + enter` to write profile and restart profiler

packages/remix-dev/cli/commands.ts

@@ -20,6 +20,7 @@ import { transpile as convertFileToJS } from "./useJavascript";
 import type { Options } from "../compiler/options";
 import { createFileWatchCache } from "../compiler/fileWatchCache";
 import { logger } from "../tux";
+import * as profiler from "../vite/profiler";
 
 type InitFlags = {
   deleteScript?: boolean;
@@ -143,7 +144,14 @@ export async function viteBuild(
   }
 
   let { build } = await import("../vite/build");
-  await build(root, options);
+  if (options.profile) {
+    await profiler.start();
+  }
+  try {
+    await build(root, options);
+  } finally {
+    profiler.stop(logger.info);
+  }
 }
 
 export async function watch(
@@ -191,6 +199,9 @@ export async function dev(
 
 export async function viteDev(root: string, options: ViteDevOptions = {}) {
   let { dev } = await import("../vite/dev");
+  if (options.profile) {
+    await profiler.start();
+  }
   await dev(root, options);
 
   // keep `remix vite-dev` alive by waiting indefinitely

packages/remix-dev/cli/run.ts

@@ -138,6 +138,7 @@ export async function run(argv: string[] = process.argv.slice(2)) {
             "-m": "--mode",
             "--open": isBooleanFlag("--open") ? Boolean : String,
             "--strictPort": Boolean,
+            "--profile": Boolean,
           }
         : {
             // Non Vite commands

packages/remix-dev/vite/build.ts

@@ -199,6 +199,7 @@ export interface ViteBuildOptions {
   logLevel?: Vite.LogLevel;
   minify?: Vite.BuildOptions["minify"];
   mode?: string;
+  profile?: boolean;
 }
 
 export async function build(

packages/remix-dev/vite/dev.ts

@@ -2,6 +2,7 @@ import type * as Vite from "vite";
 import colors from "picocolors";
 
 import { preloadViteEsm } from "./import-vite-esm-sync";
+import * as profiler from "./profiler";
 
 export interface ViteDevOptions {
   clearScreen?: boolean;
@@ -14,6 +15,7 @@ export interface ViteDevOptions {
   open?: boolean | string;
   port?: number;
   strictPort?: boolean;
+  profile?: boolean;
 }
 
 export async function dev(
@@ -53,5 +55,22 @@ export async function dev(
 
   await server.listen();
   server.printUrls();
-  server.bindCLIShortcuts({ print: true });
+
+  let customShortcuts: Vite.CLIShortcut<typeof server>[] = [
+    {
+      key: "p",
+      description: "start/stop the profiler",
+      async action(server) {
+        if (profiler.getSession()) {
+          await profiler.stop(server.config.logger.info);
+        } else {
+          await profiler.start(() => {
+            server.config.logger.info("Profiler started");
+          });
+        }
+      },
+    },
+  ];
+
+  server.bindCLIShortcuts({ print: true, customShortcuts });
 }

packages/remix-dev/vite/profiler.ts

@@ -0,0 +1,50 @@
+// Adapted from:
+// - https://github.com/vitejs/vite/blob/9fc5d9cb3a1b9df067e00959faa9da43ae03f776/packages/vite/bin/vite.js
+// - https://github.com/vitejs/vite/blob/9fc5d9cb3a1b9df067e00959faa9da43ae03f776/packages/vite/src/node/cli.ts
+
+import fs from "node:fs";
+import type { Session } from "node:inspector";
+import path from "node:path";
+import colors from "picocolors";
+
+declare namespace global {
+  let __remix_profile_session: Session | undefined;
+}
+
+export const getSession = () => global.__remix_profile_session;
+
+export const start = async (callback?: () => void | Promise<void>) => {
+  let inspector = await import("node:inspector").then((r) => r.default);
+  let session = (global.__remix_profile_session = new inspector.Session());
+  session.connect();
+  session.post("Profiler.enable", () => {
+    session.post("Profiler.start", callback);
+  });
+};
+
+let profileCount = 0;
+
+export const stop = (log: (message: string) => void): void | Promise<void> => {
+  let session = global.__remix_profile_session;
+  if (!session) return;
+  return new Promise((res, rej) => {
+    session!.post("Profiler.stop", (err: any, { profile }: any) => {
+      // Write profile to disk, upload, etc.
+      if (!err) {
+        let outPath = path.resolve(
+          `./remix-profile-${profileCount++}.cpuprofile`
+        );
+        fs.writeFileSync(outPath, JSON.stringify(profile));
+        log(
+          colors.yellow(
+            `CPU profile written to ${colors.white(colors.dim(outPath))}`
+          )
+        );
+        global.__remix_profile_session = undefined;
+        res();
+      } else {
+        rej(err);
+      }
+    });
+  });
+};