fix(scripts): detect existing dist-runtime growth (#126191)

Punchcard-Session: golden-lantern-cedar-9j

Co-authored-by: qingminlong <qing.minlong@xydigit.com>

scripts/check-gateway-watch-regression.mts

@@ -908,6 +908,9 @@ export function writeBuildAndRuntimePostBuildStamps(params: { cwd?: string } = {
   writeRuntimePostBuildStamp({ cwd });
 }
 
+export function calculateDistRuntimeByteGrowth(beforeBytes: number, afterBytes: number): number {
+  return afterBytes - beforeBytes;
+}
 /**
  * Collects pass/fail findings for the bounded gateway watch regression run.
  */
@@ -1076,10 +1079,10 @@ async function main() {
     entry.startsWith("dist-runtime/"),
   ).length;
   const distRuntimeFileGrowth = distRuntimeAddedPaths;
-  const distRuntimeByteGrowth =
-    distRuntimeAddedPaths === 0
-      ? 0
-      : post.distRuntime.apparentBytes - pre.distRuntime.apparentBytes;
+  const distRuntimeByteGrowth = calculateDistRuntimeByteGrowth(
+    pre.distRuntime.apparentBytes,
+    post.distRuntime.apparentBytes,
+  );
   const totalCpuMs = Math.round(
     (watchResult.timing.userSeconds + watchResult.timing.sysSeconds) * 1000,
   );

test/scripts/check-gateway-watch-regression.test.ts

@@ -7,6 +7,7 @@ import { describe, expect, it, vi } from "vitest";
 import {
   appendBoundedWatchLog,
   buildTimedWatchCommand,
+  calculateDistRuntimeByteGrowth,
   collectGatewayWatchFindings,
   hasGatewayReadyLog,
   parseArgs,
@@ -86,6 +87,35 @@ describe("check-gateway-watch-regression", () => {
     expect(hasGatewayReadyLog("[gateway] starting HTTP server...")).toBe(false);
   });
 
+  it("detects byte growth in existing dist-runtime paths", () => {
+    const distRuntimeByteGrowth = calculateDistRuntimeByteGrowth(100, 2_097_253);
+    const findings = collectGatewayWatchFindings({
+      cpuMs: 0,
+      distRuntimeByteGrowth,
+      distRuntimeFileGrowth: 0,
+      options: {
+        cpuFailMs: 8000,
+        cpuWarnMs: 1000,
+        distRuntimeByteGrowthMax: 2 * 1024 * 1024,
+        distRuntimeFileGrowthMax: 200,
+        windowMs: 10_000,
+      },
+      watchBuildReason: null,
+      watchResult: {
+        idleCpuMs: 0,
+        readyBeforeWindow: true,
+        spawnError: null,
+        timingFileMissing: false,
+      },
+      watchTriggeredBuild: false,
+    });
+
+    expect(distRuntimeByteGrowth).toBe(2_097_153);
+    expect(findings.failures).toContain(
+      "dist-runtime apparent byte growth 2097153 exceeded max 2097152",
+    );
+  });
+
   it("bounds in-memory watch output capture while keeping the newest logs", () => {
     const first = appendBoundedWatchLog("abc", "def", 8);
     expect(first).toEqual({ text: "abcdef", truncated: false });