improve version check speed for already downloaded versions (#21881)

As part of making it so I can locally test
[AB#8548](https://dev.azure.com/fluidframework/235294da-091d-4c29-84fc-cdfc3d90890b/_workitems/edit/8548)

I haven't tested this for remote builds, but this sped up my local runs
of loader back-compat downloads significantly from minutes to a few
seconds.

Even though the remote builds will need to download all the builds, this
speeds up the process of reading whether or not a build was installed.
My guess is that there likely will be pipeline speed reductions.

Locally, running back compat full tests will be significantly faster as
indicated above because we will not need to read the file for every
single version that we have installed, instead we will read the file
once for all installed versions.

Author: tyler-cai-microsoft

packages/test/test-version-utils/src/versionUtils.ts

@@ -18,7 +18,7 @@ import * as path from "node:path";
 import { fileURLToPath, pathToFileURL } from "node:url";
 
 import { detectVersionScheme, fromInternalScheme } from "@fluid-tools/version-tools";
-import { assert } from "@fluidframework/core-utils/internal";
+import { LazyPromise, assert } from "@fluidframework/core-utils/internal";
 import { lock } from "proper-lockfile";
 import * as semver from "semver";
 
@@ -40,6 +40,12 @@ interface InstalledJson {
 	installed: string[];
 }
 
+let cachedInstalledJson: InstalledJson | undefined;
+function writeAndUpdateInstalledJson(data: InstalledJson) {
+	cachedInstalledJson = data;
+	writeFileSync(installedJsonPath, JSON.stringify(data, undefined, 2), { encoding: "utf8" });
+}
+
 async function ensureInstalledJson() {
 	if (existsSync(installedJsonPath)) {
 		return;
@@ -54,11 +60,12 @@ async function ensureInstalledJson() {
 		mkdirSync(baseModulePath, { recursive: true });
 		const data: InstalledJson = { revision, installed: [] };
 
-		writeFileSync(installedJsonPath, JSON.stringify(data, undefined, 2), { encoding: "utf8" });
+		writeAndUpdateInstalledJson(data);
 	} finally {
 		release();
 	}
 }
+const ensureInstalledJsonLazy = new LazyPromise(async () => ensureInstalledJson());
 
 function readInstalledJsonNoLock(): InstalledJson {
 	const data = readFileSync(installedJsonPath, { encoding: "utf8" });
@@ -67,46 +74,47 @@ function readInstalledJsonNoLock(): InstalledJson {
 		// if the revision doesn't match assume that it doesn't match
 		return { revision, installed: [] };
 	}
+	cachedInstalledJson = installedJson;
 	return installedJson;
 }
 
 async function readInstalledJson(): Promise<InstalledJson> {
-	await ensureInstalledJson();
+	await ensureInstalledJsonLazy;
 	const release = await lock(installedJsonPath, { retries: { forever: true } });
 	try {
 		return readInstalledJsonNoLock();
 	} finally {
 		release();
 	}
 }
+const readInstalledJsonLazy = new LazyPromise(async () => readInstalledJson());
+async function getInstalledJson(): Promise<InstalledJson> {
+	return cachedInstalledJson ?? (await readInstalledJsonLazy);
+}
 
 const isInstalled = async (version: string) =>
-	(await readInstalledJson()).installed.includes(version);
+	(await getInstalledJson()).installed.includes(version);
 async function addInstalled(version: string) {
-	await ensureInstalledJson();
+	await ensureInstalledJsonLazy;
 	const release = await lock(installedJsonPath, { retries: { forever: true } });
 	try {
 		const installedJson = readInstalledJsonNoLock();
 		if (!installedJson.installed.includes(version)) {
 			installedJson.installed.push(version);
-			writeFileSync(installedJsonPath, JSON.stringify(installedJson, undefined, 2), {
-				encoding: "utf8",
-			});
+			writeAndUpdateInstalledJson(installedJson);
 		}
 	} finally {
 		release();
 	}
 }
 
 async function removeInstalled(version: string) {
-	await ensureInstalledJson();
+	await ensureInstalledJsonLazy;
 	const release = await lock(installedJsonPath, { retries: { forever: true } });
 	try {
 		const installedJson = readInstalledJsonNoLock();
 		installedJson.installed = installedJson.installed.filter((value) => value !== version);
-		writeFileSync(installedJsonPath, JSON.stringify(installedJson, undefined, 2), {
-			encoding: "utf8",
-		});
+		writeAndUpdateInstalledJson(installedJson);
 	} finally {
 		release();
 	}