fix(typescript-checker): support TS 4.4 (#3178)

TypeScript 4.4 also watches package.json files in node_modules for changes. I guess this is done to be able to reload the types when a node_module gets updated.

However, the typescript-checker wasn't expecting those `watchFile` calls to come in. The checker was defensive programmed, meaning an error is thrown when something happens that it doesn't expect.

This ended up being a simple fix. Simply ignoring `watchFile` of files that are not loaded seems to do the trick.

e2e/package.json

@@ -39,7 +39,7 @@
     "ts-jest": "~27.0.1",
     "ts-loader": "~8.0.3",
     "ts-node": "~7.0.0",
-    "typescript": "~4.3.2",
+    "typescript": "^4.4.3",
     "webpack": "~4.41.2",
     "webpack-cli": "~3.3.12"
   },

e2e/test/jest-with-ts/stryker.conf.json

@@ -13,8 +13,8 @@
   ],
   "coverageAnalysis": "off",
   "reporters": [
-    "event-recorder",
     "progress",
-    "html"
+    "html",
+    "json"
   ]
 }

e2e/test/jest-with-ts/verify/verify.ts

@@ -1,16 +1,15 @@
-import { expectMetrics } from '../../../helpers';
+import { expectMetricsJson } from '../../../helpers';
 
 describe('Verify stryker has ran correctly', () => {
-
   it('should report correct score', async () => {
-    await expectMetrics({
+    await expectMetricsJson({
       ignored: 0,
       killed: 17,
-      mutationScore: 56.67,
+      mutationScore: 62.96,
       noCoverage: 0,
-      survived: 13,
+      survived: 10,
       timeout: 0,
-      compileErrors: 32
+      compileErrors: 35,
     });
   });
 });

packages/typescript-checker/.vscode/launch.json

@@ -4,7 +4,7 @@
     {
       "type": "node",
       "request": "launch",
-      "name": "Unit / Integration tests",
+      "name": "💙 Unit / Integration tests",
       "program": "${workspaceRoot}/../../node_modules/mocha/bin/_mocha",
       "internalConsoleOptions": "openOnSessionStart",
       "outFiles": [

packages/typescript-checker/src/fs/hybrid-file-system.ts

@@ -47,11 +47,10 @@ export class HybridFileSystem {
 
   public watchFile(fileName: string, watcher: ts.FileWatcherCallback): void {
     const file = this.getFile(fileName);
-    if (!file) {
-      throw new Error(`Cannot find file ${fileName} for watching`);
+    if (file) {
+      this.log.trace('Registering watcher for file "%s"', fileName);
+      file.watcher = watcher;
     }
-    this.log.trace('Registering watcher for file "%s"', fileName);
-    file.watcher = watcher;
   }
 
   public getFile(fileName: string): ScriptFile | undefined {

packages/typescript-checker/test/unit/fs/hybrid-file-system.spec.ts

@@ -1,7 +1,7 @@
 import sinon from 'sinon';
 import ts from 'typescript';
 import { expect } from 'chai';
-import { testInjector } from '@stryker-mutator/test-helpers';
+import { factory, testInjector } from '@stryker-mutator/test-helpers';
 
 import { HybridFileSystem } from '../../../src/fs';
 
@@ -106,8 +106,14 @@ describe('fs', () => {
         expect(helper.readFileStub).calledWith('test/foo/a.js');
       });
 
-      it("should throw if file doesn't exist", () => {
-        expect(() => sut.watchFile('not-exists.js', sinon.stub())).throws('Cannot find file not-exists.js for watching');
+      it("should not throw if file isn't loaded", () => {
+        // Should ignore the file watch
+        const watchCallback = sinon.stub();
+        sut.watchFile('node_modules/chai/package.json', watchCallback);
+
+        // If it was successfully ignored, than `mutate` should throw
+        expect(() => sut.mutate(factory.mutant({ fileName: 'node_modules/chai/package.json' }))).throws();
+        expect(watchCallback).not.called;
       });
 
       it('should log that the file is watched', () => {