Support mocha's --posix-exit-codes option.

[73rhodes]

This PR adds support for mocha's new --posix-exit-codes command line option. When this option is given, mocha will exit using standard posix exit codes instead of using he number of failed tests as the exit code. This avoids situations like out-of-memory errors causing CICD pipelines that use ts-mocha from failing silently.

[gemini-code-assist]

Summary of Changes

Hello @73rhodes, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances ts-mocha by integrating support for Mocha's --posix-exit-codes option. This modification ensures that ts-mocha exits with standard POSIX-compliant codes when a fatal signal is encountered, which is crucial for robust error handling and preventing silent failures in automated CI/CD environments. The change also includes necessary documentation updates.

Highlights

• New Feature: POSIX Exit Codes: This pull request introduces support for Mocha's --posix-exit-codes option, enabling ts-mocha to exit with standard POSIX codes (128 + signal number) when a fatal signal is received, rather than the number of failed tests.
• Improved CI/CD Reliability: The change addresses a critical issue where ts-mocha could fail silently in CI/CD pipelines due to non-standard exit codes, particularly in scenarios involving out-of-memory errors or other fatal signals, by ensuring a clear, standard exit status.
• Documentation Update: The README.md has been updated to clearly document the newly supported --posix-exit-codes command-line option, providing users with information on its purpose and usage.

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[gemini-code-assist]

Code Review

This pull request introduces support for a --posix-exit-codes flag, which makes ts-mocha exit with POSIX-compliant codes when the underlying mocha process is terminated by a signal. The implementation is mostly correct, but I've pointed out a few areas for improvement. The most critical one is the use of process.exit() within a process.on('exit') handler, which should be avoided. I've also suggested some minor improvements for code clarity and documentation structure.

[gemini-code-assist]

This block has a few areas for improvement:

1. high: Calling process.exit() inside a process.on('exit') event handler is not recommended. The process is already exiting, so you should only set process.exitCode and let Node.js handle the termination. The explicit process.exit() call is redundant and can prevent other 'exit' listeners from running.
2. medium: The expression 128 + os.constants.signals[signal] is calculated multiple times. It's better to compute it once and store it in a constant for improved readability and efficiency.
3. medium: It's a good practice in JavaScript to use strict equality (===) instead of loose equality (==) to prevent unexpected type coercion.

      if (process.env.POSIX_EXIT_CODES === 'true') {
        const exitCode = 128 + os.constants.signals[signal];
        console.warn(`ts-mocha exiting with code ${exitCode}`);
        process.exitCode = exitCode;
      } else {
        console.warn(`ts-mocha killing process with ${signal}; process.exitCode ${process.exitCode}`);
        process.kill(process.pid, signal);
      }

[gemini-code-assist]

While adding documentation for the new flag is great, its current placement interrupts the flow between the --project option and its corresponding example. For better readability, consider moving this new option to be grouped with the other option flags, for instance, after the --type-check flag's section.

[gemini-code-assist]

The comment // add when supported by mocha is confusing. The pull request description states this is for "mocha's new --posix-exit-codes command line option", which implies mocha does support this option. If that's the case, this comment is misleading and should be removed. If mocha does not support this option, passing it might cause an "unrecognized option" error.

      mochaArgs.push(arg);

[Copilot]

Pull Request Overview

This PR adds support for mocha's --posix-exit-codes command line option to ts-mocha, enabling standard POSIX exit codes instead of using the number of failed tests as the exit code.

• Adds documentation for the new --posix-exit-codes option in the README

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