DevTools: Separate named hooks I/O and CPU code

I/O code has been moved into a file (loadSourceAndMetadata) that runs on the main/UI thread. CPU code has been moved into a file (parseSourceAndMetadata) that runs in a web worker (except for Jest tests).

This is being done to increase the likelihood of re-using cached source files when fetching from the network.

packages/react-devtools-extensions/src/__tests__/parseHookNames-test.js

@@ -42,7 +42,24 @@ describe('parseHookNames', () => {
 
     inspectHooks = require('react-debug-tools/src/ReactDebugHooks')
       .inspectHooks;
-    parseHookNames = require('../parseHookNames/parseHookNames').parseHookNames;
+
+    // Jest can't run the workerized version of this module.
+    const loadSourceAndMetadata = require('../parseHookNames/loadSourceAndMetadata')
+      .default;
+    const parseSourceAndMetadata = require('../parseHookNames/parseSourceAndMetadata')
+      .parseSourceAndMetadata;
+    parseHookNames = async hooksTree => {
+      const [
+        hooksList,
+        locationKeyToHookSourceAndMetadata,
+      ] = await loadSourceAndMetadata(hooksTree);
+
+      // Runs in a Worker because it's CPU intensive:
+      return parseSourceAndMetadata(
+        hooksList,
+        locationKeyToHookSourceAndMetadata,
+      );
+    };
 
     // Jest (jest-runner?) configures Errors to automatically account for source maps.
     // This changes behavior between our tests and the browser.
@@ -880,18 +897,21 @@ describe('parseHookNames', () => {
 describe('parseHookNames worker', () => {
   let inspectHooks;
   let parseHookNames;
-  let workerizedParseHookNamesMock;
+  let workerizedParseSourceAndMetadataMock;
 
   beforeEach(() => {
     window.Worker = undefined;
 
-    workerizedParseHookNamesMock = jest.fn();
+    workerizedParseSourceAndMetadataMock = jest.fn(() => {
+      console.log('mock fn');
+      return [];
+    });
 
-    jest.mock('../parseHookNames/parseHookNames.worker.js', () => {
+    jest.mock('../parseHookNames/parseSourceAndMetadata.worker.js', () => {
       return {
         __esModule: true,
         default: () => ({
-          parseHookNames: workerizedParseHookNamesMock,
+          parseSourceAndMetadata: workerizedParseSourceAndMetadataMock,
         }),
       };
     });
@@ -912,11 +932,12 @@ describe('parseHookNames worker', () => {
       .Component;
 
     window.Worker = true;
-    // resets module so mocked worker instance can be updated
+
+    // Reset module so mocked worker instance can be updated.
     jest.resetModules();
     parseHookNames = require('../parseHookNames').parseHookNames;
 
     await getHookNamesForComponent(Component);
-    expect(workerizedParseHookNamesMock).toHaveBeenCalledTimes(1);
+    expect(workerizedParseSourceAndMetadataMock).toHaveBeenCalledTimes(1);
   });
 });

packages/react-devtools-extensions/src/parseHookNames/index.js

@@ -7,17 +7,38 @@
  * @flow
  */
 
-// This file uses workerize to load ./parseHookNames.worker as a webworker and instanciates it,
-// exposing flow typed functions that can be used on other files.
+import type {HookSourceAndMetadata} from './loadSourceAndMetadata';
+import type {HooksNode, HooksTree} from 'react-debug-tools/src/ReactDebugHooks';
+import type {HookNames} from 'react-devtools-shared/src/types';
 
-import WorkerizedParseHookNames from './parseHookNames.worker';
-import typeof * as ParseHookNamesModule from './parseHookNames';
+import WorkerizedParseSourceAndMetadata from './parseSourceAndMetadata.worker';
+import typeof * as ParseSourceAndMetadataModule from './parseSourceAndMetadata';
 
-const workerizedParseHookNames: ParseHookNamesModule = WorkerizedParseHookNames();
+import loadSourceAndMetadata from './loadSourceAndMetadata';
 
-type ParseHookNames = $PropertyType<ParseHookNamesModule, 'parseHookNames'>;
+const workerizedParseHookNames: ParseSourceAndMetadataModule = WorkerizedParseSourceAndMetadata();
 
-export const parseHookNames: ParseHookNames = hooksTree =>
-  workerizedParseHookNames.parseHookNames(hooksTree);
+export function parseSourceAndMetadata(
+  hooksList: Array<HooksNode>,
+  locationKeyToHookSourceAndMetadata: Map<string, HookSourceAndMetadata>,
+): Promise<HookNames | null> {
+  return workerizedParseHookNames.parseSourceAndMetadata(
+    hooksList,
+    locationKeyToHookSourceAndMetadata,
+  );
+}
 
 export const purgeCachedMetadata = workerizedParseHookNames.purgeCachedMetadata;
+
+export async function parseHookNames(
+  hooksTree: HooksTree,
+): Promise<HookNames | null> {
+  // Runs on the main/UI thread so it can reuse Network cache:
+  const [
+    hooksList,
+    locationKeyToHookSourceAndMetadata,
+  ] = await loadSourceAndMetadata(hooksTree);
+
+  // Runs in a Worker because it's CPU intensive:
+  return parseSourceAndMetadata(hooksList, locationKeyToHookSourceAndMetadata);
+}