Convert require calls to imports

Although the existing require calls would work fine, it's more
consistent to make them actual imports and let them be converted at
compile/bundle time. It also lets us emit ESM if needed.

There are still conditional requires present for things like the node
System, but that's a more difficult problem to solve.

src/cancellationToken/cancellationToken.ts

@@ -1,6 +1,6 @@
 /// <reference types="node"/>
 
-import fs = require("fs");
+import * as fs from "fs";
 
 interface ServerCancellationToken {
     isCancellationRequested(): boolean;

src/harness/findUpDir.ts

@@ -1,5 +1,5 @@
-const { join, resolve, dirname } = require("path") as typeof import("path");
-const { existsSync } = require("fs") as typeof import("fs");
+import { existsSync } from "fs";
+import { dirname, join, resolve } from "path";
 
 // search directories upward to avoid hard-wired paths based on the
 // build tree (same as scripts/build/findUpDir.js)

src/harness/harnessGlobals.ts

@@ -1,19 +1,17 @@
-import * as ts from "./_namespaces/ts";
+import * as chai from "chai";
 
-// Block scoped definitions work poorly for global variables, temporarily enable var
-/* eslint-disable no-var */
+import * as ts from "./_namespaces/ts";
 
 // this will work in the browser via browserify
 declare global {
     // Module transform: converted from ambient declaration
-    var assert: typeof _chai.assert;
+    var assert: typeof chai.assert; // eslint-disable-line no-var
 }
 declare global {
     // Module transform: converted from ambient declaration
-    var expect: typeof _chai.expect;
+    var expect: typeof chai.expect; // eslint-disable-line no-var
 }
-var _chai: typeof import("chai") = require("chai");
-globalThis.assert = _chai.assert;
+globalThis.assert = chai.assert;
 {
     // chai's builtin `assert.isFalse` is featureful but slow - we don't use those features,
     // so we'll just overwrite it as an alterative to migrating a bunch of code off of chai
@@ -39,7 +37,7 @@ globalThis.assert = _chai.assert;
         }
     };
 }
-globalThis.expect = _chai.expect;
-/* eslint-enable no-var */
+globalThis.expect = chai.expect;
+
 // empty ts namespace so this file is included in the `ts.ts` namespace file generated by the module swapover
-// This way, everything that ends up importing `ts` downstream also imports this file and picks up its augmentation
+// This way, everything that ends up importing `ts` downstream also imports this file and picks up its augmentation

src/testRunner/externalCompileRunner.ts

@@ -1,10 +1,10 @@
+import * as del from "del";
+import * as fs from "fs";
+import * as path from "path";
+
 import * as ts from "./_namespaces/ts";
 import { Baseline, IO, isWorker, RunnerBase, TestRunnerKind } from "./_namespaces/Harness";
 
-const fs: typeof import("fs") = require("fs");
-const path: typeof import("path") = require("path");
-const del: typeof import("del") = require("del");
-
 interface ExecResult {
     stdout: Buffer;
     stderr: Buffer;

src/testRunner/unittests/services/languageService.ts

@@ -1,7 +1,7 @@
+import { expect } from "chai";
+
 import * as ts from "../../_namespaces/ts";
 
-const _chai: typeof import("chai") = require("chai");
-const expect: typeof _chai.expect = _chai.expect;
 describe("unittests:: services:: languageService", () => {
     const files: {[index: string]: string} = {
         "foo.ts": `import Vue from "./vue";

src/testRunner/unittests/tsserver/session.ts

@@ -1,9 +1,9 @@
+import { expect } from "chai";
+
 import * as ts from "../../_namespaces/ts";
 import * as Harness from "../../_namespaces/Harness";
 import * as Utils from "../../_namespaces/Utils";
 
-const _chai: typeof import("chai") = require("chai");
-const expect: typeof _chai.expect = _chai.expect;
 let lastWrittenToHost: string;
 const noopFileWatcher: ts.FileWatcher = { close: ts.noop };
 const mockHost: ts.server.ServerHost = {

src/typingsInstaller/nodeTypingsInstaller.ts

@@ -1,3 +1,6 @@
+import * as fs from "fs";
+import * as path from "path";
+
 import {
     installNpmPackages, Log, RequestCompletedAction, TypingsInstaller,
 } from "./_namespaces/ts.server.typingsInstaller";
@@ -11,16 +14,6 @@ import {
     MapLike, normalizeSlashes, stringContains, sys, toPath, version,
 } from "./_namespaces/ts";
 
-const fs: {
-    appendFileSync(file: string, content: string): void
-} = require("fs");
-
-const path: {
-    join(...parts: string[]): string;
-    dirname(path: string): string;
-    basename(path: string, extension?: string): string;
-} = require("path");
-
 class FileLog implements Log {
     constructor(private logFile: string | undefined) {
     }

src/watchGuard/watchGuard.ts

@@ -1,10 +1,9 @@
-/// <reference types="node" />
+import * as fs from "fs";
 
 if (process.argv.length < 3) {
     process.exit(1);
 }
 const directoryName = process.argv[2];
-const fs: { watch(directoryName: string, options: any, callback: () => {}): any } = require("fs");
 // main reason why we need separate process to check if it is safe to watch some path
 // is to guard against crashes that cannot be intercepted with protected blocks and
 // code in tsserver already can handle normal cases, like non-existing folders.