From 77c535ce25575e0679d7df8d40afe4dcce1d3c1f Mon Sep 17 00:00:00 2001
From: mofeiZ <34200447+mofeiZ@users.noreply.github.com>
Date: Thu, 11 May 2023 14:58:51 -0400
Subject: [PATCH] [snap] Make watch mode go fast(er)

While optimizing per @josephsavona's suggestions in #1592, I noticed that we
were clearing quite a few require cache entries.

As of this PR, `Object.keys(require.cache)` holds

- 1258 entries total

- 67 files compiled from Forget source code (this is what
`ts.createWatchCompilerHost` modifies)

- 1120 babel source files (from node_modules)

When working on watch mode, I'm almost always making changes to Forget source or
test fixture files. It's a bit faster to just clear those entries (assuming that
babel has no global state we need to invalidate).

On my computer, re-running tests in watch mode (triggered by source code
changes) takes:

|   |  All tests  | One test (filter) |

|-- |--------|----------|

| current | 4.7s  | 1.8s  |

| this PR  |  1.8s  | 0.1s  |
---
 .../packages/snap/src/compiler-worker.ts      | 20 +++++--------------
 compiler/forget/packages/snap/src/runner.ts   |  3 ++-
 2 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/compiler/forget/packages/snap/src/compiler-worker.ts b/compiler/forget/packages/snap/src/compiler-worker.ts
index ce65610b35..cedd9c226f 100644
--- a/compiler/forget/packages/snap/src/compiler-worker.ts
+++ b/compiler/forget/packages/snap/src/compiler-worker.ts
@@ -11,24 +11,14 @@ import { exists } from "./utils";
 
 const originalConsoleError = console.error;
 
-// Subpaths to ignore when clearing the require cache
-const ignoredRequireSubpaths: Array<string> = [
-  // compiler worker runner files
-  "node_modules/jest-worker",
-  // snap source files
-  "packages/snap",
-];
-const ignoredRequirePaths: Set<string> = new Set(
-  Object.keys(require.cache).filter(
-    (path) =>
-      !ignoredRequireSubpaths.every((ignored) => !path.includes(ignored))
-  )
-);
-
+// Try to avoid clearing the entire require cache, which (as of this PR)
+// contains ~1250 files. This assumes that no dependencies have global caches
+// that may need to be invalidated across Forget reloads.
+const invalidationSubpath = "react-forget/forget/dist";
 let version: number | null = null;
 export function clearRequireCache() {
   Object.keys(require.cache).forEach(function (path) {
-    if (!ignoredRequirePaths.has(path)) {
+    if (path.includes(invalidationSubpath)) {
       delete require.cache[path];
     }
   });
diff --git a/compiler/forget/packages/snap/src/runner.ts b/compiler/forget/packages/snap/src/runner.ts
index 89665c8cb9..97063189c9 100644
--- a/compiler/forget/packages/snap/src/runner.ts
+++ b/compiler/forget/packages/snap/src/runner.ts
@@ -441,13 +441,14 @@ export async function main(opts: RunnerOptions): Promise<void> {
         const start = performance.now();
         clearConsole();
         console.log("Running tests...");
+        // we don't clear console after this point, since
+        // it may contain debug console logging
         const results = await run(
           worker,
           opts,
           filterMode ? testFilter : null,
           compilerVersion
         );
-        clearConsole();
         if (mode === Mode.Update) {
           update(results);
         } else {