Enable run-detect-module-type test and fix its import.cjs fixtures

test/cli/run/module-type-fixture/cjs/import.cjs

@@ -1,3 +1,3 @@
 import * as fs from "node:fs";
 console.log(eval("typeof module === 'undefined'"));
-+fs;
+fs.constants;

test/cli/run/module-type-fixture/esm/import.cjs

@@ -1,3 +1,3 @@
 import * as fs from "node:fs";
 console.log(eval("typeof module === 'undefined'"));
-+fs;
+fs.constants;

test/cli/run/run-detect-module-type.test.ts

@@ -0,0 +1,61 @@
+import { expect, test } from "bun:test";
+import { bunEnv, bunExe } from "harness";
+import { join } from "path";
+
+// package.json "type" -> file name -> expected module type of the main entry
+const table = {
+  cjs: {
+    "hello.cjs": "commonjs",
+    "hello.js": "commonjs",
+    "hello.mjs": "module",
+    "hello.ts": "commonjs",
+    "hello.tsx": "module",
+    "hello.cts": "commonjs",
+    "hello.jsx": "module",
+    "hello.mts": "module",
+    // files using ES import and no exports will be detected as module
+    "import.cjs": "module",
+  },
+  esm: {
+    "hello.cjs": "commonjs",
+    "hello.js": "module",
+    "hello.mjs": "module",
+    "hello.ts": "module",
+    "hello.tsx": "module",
+    "hello.cts": "commonjs",
+    "hello.jsx": "module",
+    "hello.mts": "module",
+    // files using ES import and no exports will be detected as module
+    "import.cjs": "module",
+  },
+} as const;
+
+const cases = Object.entries(table).flatMap(([packageType, files]) =>
+  Object.entries(files).map(([file, expectedType]) => ({ packageType, file, expectedType })),
+);
+
+test("detect module type", async () => {
+  // each fixture prints `typeof module === 'undefined'`: "false" means it ran as commonjs
+  const actual = await Promise.all(
+    cases.map(async ({ packageType, file }) => {
+      await using proc = Bun.spawn({
+        cmd: [bunExe(), "run", join(import.meta.dir, "module-type-fixture", packageType, file)],
+        env: bunEnv,
+        stdout: "pipe",
+        stderr: "pipe",
+      });
+      const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+      if (exitCode !== 0) {
+        throw new Error(`Failed to run ${packageType}/${file}: ${stderr.trim()}`);
+      }
+      const out = stdout.trim();
+      const detected =
+        out === "true" ? "module" : out === "false" ? "commonjs" : `unexpected output ${JSON.stringify(out)}`;
+      return `${packageType} ${file} -> ${detected}`;
+    }),
+  );
+
+  expect(actual).toEqual(
+    cases.map(({ packageType, file, expectedType }) => `${packageType} ${file} -> ${expectedType}`),
+  );
+});