perf(scripts): emit a server module beside the runtime bundle entry (#16765)

The runtime bundle now also has a server entry point, dist-runtime/server.mjs: the bundled dist/index.js without the argv shim. index.mjs loads it, so importing server.mjs loads the server code without starting it, and a compile cache warmed from it covers exactly the files a boot loads. bundleRuntime reports it as serverModule.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

server/scripts/bundle-runtime.mjs

@@ -74,7 +74,7 @@ function externalizeThirdParty(isBundled, runtimeDir) {
 export async function bundleRuntime({ entry, outdir, isBundled = (specifier) => specifier.startsWith("@paperclipai/") }) {
   await rm(outdir, { recursive: true, force: true });
   const result = await build({
-    entryPoints: { index: "paperclip-runtime-entry" },
+    entryPoints: { index: "paperclip-runtime-entry", server: entry },
     outdir,
     outExtension: { ".js": ".mjs" },
     chunkNames: "chunk-[hash]",
@@ -92,7 +92,12 @@ export async function bundleRuntime({ entry, outdir, isBundled = (specifier) =>
     plugins: [runtimeEntry(entry), keepModuleLocations, externalizeThirdParty(isBundled, dirname(entry))],
   });
   const outputs = Object.keys(result.metafile.outputs).filter((file) => file.endsWith(".mjs"));
-  return { outfile: join(outdir, "index.mjs"), inputs: Object.keys(result.metafile.inputs).length, chunks: outputs.length };
+  return {
+    outfile: join(outdir, "index.mjs"),
+    serverModule: join(outdir, "server.mjs"),
+    inputs: Object.keys(result.metafile.inputs).length,
+    chunks: outputs.length,
+  };
 }
 
 async function main() {

server/scripts/bundle-runtime.test.mjs

@@ -2,6 +2,7 @@ import { execFile } from "node:child_process";
 import { mkdirSync, mkdtempSync, realpathSync, rmSync, symlinkSync, writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import path from "node:path";
+import { pathToFileURL } from "node:url";
 import { promisify } from "node:util";
 
 import { afterEach, beforeEach, describe, expect, it } from "vitest";
@@ -84,6 +85,18 @@ describe("bundleRuntime", () => {
     expect(output.entryDir).toBe(path.join(root, "server", "dist"));
   });
 
+  it("emits a server module that loads without starting the server", async () => {
+    const outdir = path.join(root, "server", "dist-runtime");
+    const summary = await bundleRuntime({ entry: path.join(root, "server", "dist", "index.js"), outdir });
+    expect(summary.serverModule).toBe(path.join(outdir, "server.mjs"));
+    const probe = path.join(root, "server", "probe.mjs");
+    write(probe, `await import(${JSON.stringify(pathToFileURL(summary.serverModule).href)});\nconsole.log("loaded");\n`);
+    const loaded = await execFileAsync(process.execPath, [probe], { cwd: path.join(root, "server"), timeout: 30_000 });
+    expect(loaded.stdout.trim()).toBe("loaded");
+    const started = await execFileAsync(process.execPath, [summary.outfile], { cwd: path.join(root, "server"), timeout: 30_000 });
+    expect(JSON.parse(started.stdout).late).toBe(43);
+  });
+
   it("leaves the server's own dependencies to runtime resolution", async () => {
     const outdir = path.join(root, "server", "dist-runtime");
     const summary = await bundleRuntime({ entry: path.join(root, "server", "dist", "index.js"), outdir });