fix(node): add missing process.reallyExit method (#19326)

This PR adds the missing `process.reallyExit()` method to node's
`process` object.

Was [pinged on
twitter](https://twitter.com/biwanczuk/status/1663326659787862017)
regarding running the `fastify` test suite in node. They use `node-tap`
which has been around arguably the longest of the test frameworks and
relies on a couple of old APIs. They have `signal-exit` as a dependency
which in turn [makes use of
`process.reallyExit()`](8fa7fc9a9c/src/index.ts (L19)).
That function cannot be found anywhere in their documentation, but
exists at runtime. See
6a6b3c5402/lib/internal/bootstrap/node.js (L172)

This doesn't yet make `node-tap` work, but gets us one step closer.

cli/tests/unit_node/process_test.ts

@@ -727,3 +727,22 @@ Deno.test({
     assertEquals(stripColor(decoder.decode(stdout).trim()), "exit");
   },
 });
+
+Deno.test({
+  name: "process.reallyExit",
+  async fn() {
+    const command = new Deno.Command(Deno.execPath(), {
+      args: [
+        "run",
+        "--quiet",
+        "--unstable",
+        "./testdata/process_really_exit.ts",
+      ],
+      cwd: testDir,
+    });
+    const { stdout } = await command.output();
+
+    const decoder = new TextDecoder();
+    assertEquals(stripColor(decoder.decode(stdout).trim()), "really exited");
+  },
+});

cli/tests/unit_node/testdata/process_really_exit.ts

@@ -0,0 +1,10 @@
+import process from "node:process";
+
+//deno-lint-ignore no-undef
+// @ts-ignore - Node typings don't even have this because it's
+// been deprecated for 4 years. But it's used in `signal-exit`,
+// which in turn is used in `node-tap`.
+process.reallyExit = function () {
+  console.info("really exited");
+};
+process.exit();

ext/node/polyfills/process.ts

@@ -91,7 +91,7 @@ export const exit = (code?: number | string) => {
     process.emit("exit", process.exitCode || 0);
   }
 
-  Deno.exit(process.exitCode || 0);
+  process.reallyExit(process.exitCode || 0);
 };
 
 function addReadOnlyProcessAlias(
@@ -380,6 +380,13 @@ class Process extends EventEmitter {
   /** https://nodejs.org/api/process.html#process_process_exit_code */
   exit = exit;
 
+  // Undocumented Node API that is used by `signal-exit` which in turn
+  // is used by `node-tap`. It was marked for removal a couple of years
+  // ago. See https://github.com/nodejs/node/blob/6a6b3c54022104cc110ab09044a2a0cecb8988e7/lib/internal/bootstrap/node.js#L172
+  reallyExit = (code: number) => {
+    return Deno.exit(code || 0);
+  };
+
   _exiting = _exiting;
 
   /** https://nodejs.org/api/process.html#processexitcode_1 */