feat: Add `Deno.exitCode` API (#23609)

This commits adds the ability to set a would-be exit code 
for the Deno process without forcing an immediate exit, 
through the new `Deno.exitCode` API.

- **Implements `Deno.exitCode` getter and setter**: Adds support for
setting
and retrieving a would-be exit code via `Deno.exitCode`.
This allows for asynchronous cleanup before process termination 
without immediately exiting.
- **Ensures type safety**: The setter for `Deno.exitCode` validates that
the provided value is a number, throwing a TypeError if not, to ensure
that
only valid exit codes are set.

Closes to #23605

---------

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/cli/tsc/dts/lib.deno.ns.d.ts b/cli/tsc/dts/lib.deno.ns.d.ts
index 76b59761c..cf8e4ba05 100644
--- a/cli/tsc/dts/lib.deno.ns.d.ts
+++ b/cli/tsc/dts/lib.deno.ns.d.ts
@@ -1466,6 +1466,23 @@ declare namespace Deno {
    */
   export function exit(code?: number): never;
 
+  /** The exit code for the Deno process.
+   *
+   * If no exit code has been supplied, then Deno will assume a return code of `0`.
+   *
+   * When setting an exit code value, a number or non-NaN string must be provided,
+   * otherwise a TypeError will be thrown.
+   *
+   * ```ts
+   * console.log(Deno.exitCode); //-> 0
+   * Deno.exitCode = 1;
+   * console.log(Deno.exitCode); //-> 1
+   * ```
+   *
+   * @category Runtime
+   */
+  export var exitCode: number;
+
   /** An interface containing methods to interact with the process environment
    * variables.
    *