cli: remove redundant caching from jest module loader

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/cli/config/jest.js

@@ -25,11 +25,6 @@ const envOptions = {
   enableSourceMaps: Boolean(process.env.ENABLE_SOURCE_MAPS),
 };
 
-if (!envOptions.oldTests) {
-  // Needed so that, at import-time, it can hook into Jest's internals.
-  require('./jestCachingModuleLoader');
-}
-
 const transformIgnorePattern = [
   '@material-ui',
   'ajv',

packages/cli/config/jestCachingModuleLoader.js

@@ -14,61 +14,11 @@
  * limitations under the License.
  */
 
-const fs = require('fs');
 const { default: JestRuntime } = require('jest-runtime');
 
-const fileTransformCache = new Map();
 const scriptTransformCache = new Map();
 
-let runtimeGeneration = 0;
-let isWatchMode;
-
 module.exports = class CachingJestRuntime extends JestRuntime {
-  // Each Jest run creates a new runtime, including when rerunning tests in
-  // watch mode. This keeps track of whether we've switched runtime instance.
-  __runtimeGeneration = runtimeGeneration++;
-
-  transformFile(filename, options) {
-    if (!isWatchMode) {
-      return super.transformFile(filename, options);
-    }
-
-    const entry = fileTransformCache.get(filename);
-    if (entry) {
-      // Only check modification time if it's from a different runtime generation
-      if (entry.generation === this.__runtimeGeneration) {
-        return entry.code;
-      }
-
-      // Keep track of the modification time of files so that we can properly
-      // reprocess them in watch mode.
-      const { mtimeMs } = fs.statSync(filename);
-      if (mtimeMs > entry.mtimeMs) {
-        const code = super.transformFile(filename, options);
-        fileTransformCache.set(filename, {
-          code,
-          mtimeMs,
-          generation: this.__runtimeGeneration,
-        });
-        return code;
-      }
-
-      fileTransformCache.set(filename, {
-        ...entry,
-        generation: this.__runtimeGeneration,
-      });
-      return entry.code;
-    }
-
-    const code = super.transformFile(filename, options);
-    fileTransformCache.set(filename, {
-      code,
-      mtimeMs: fs.statSync(filename).mtimeMs,
-      generation: this.__runtimeGeneration,
-    });
-    return code;
-  }
-
   // This may or may not be a good idea. Theoretically I don't know why this would impact
   // test correctness and flakiness, but it seems like it may introduce flakiness and strange failures.
   // It does seem to speed up test execution by a fair amount though.
@@ -84,11 +34,3 @@ module.exports = class CachingJestRuntime extends JestRuntime {
     return script;
   }
 };
-
-// Inject hook into createHasteMap, as it's the only way that we can
-// determine (from our scope here) if we're in "watch mode" or not.
-const originalCreateHasteMap = JestRuntime.createHasteMap;
-JestRuntime.createHasteMap = (config, options = undefined) => {
-  isWatchMode = options && options.watch;
-  return originalCreateHasteMap(config, options);
-};