test: test snapshotting TypeScript compiler

PR-URL: #38905
Refs: #35711
Reviewed-By: Chengzhong Wu <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>

test/fixtures/snapshot/ts-example.js

@@ -0,0 +1,8 @@
+var VirtualPoint = /** @class */ (function () {
+    function VirtualPoint(x, y) {
+        this.x = x;
+        this.y = y;
+    }
+    return VirtualPoint;
+}());
+var newVPoint = new VirtualPoint(13, 56);

test/fixtures/snapshot/ts-example.ts

@@ -0,0 +1,11 @@
+class VirtualPoint {
+  x: number;
+  y: number;
+
+  constructor(x: number, y: number) {
+    this.x = x;
+    this.y = y;
+  }
+}
+
+const newVPoint = new VirtualPoint(13, 56);

test/fixtures/snapshot/typescript-main.js

@@ -0,0 +1,28 @@
+// This file is to be concatenated with
+// https://github.com/microsoft/TypeScript/blob/main/lib/typescript.js
+// to produce a snapshot that reads a file path from the command
+// line and compile it into JavaScript, then write the
+// result into another file.
+
+const fs = require('fs');
+const v8 = require('v8');
+const assert = require('assert');
+
+v8.startupSnapshot.setDeserializeMainFunction(( { ts }) => {
+  const input = process.argv[1];
+  const output = process.argv[2];
+  console.error(`Compiling ${input} to ${output}`);
+  assert(input);
+  assert(output);
+  const source = fs.readFileSync(input, 'utf8');
+
+  let result = ts.transpileModule(
+    source,
+    {
+      compilerOptions: {
+        module: ts.ModuleKind.CommonJS
+      }
+    });
+
+  fs.writeFileSync(output, result.outputText, 'utf8');
+}, { ts });