How to prevent WP-CLI shell from exiting when an exception occurs?

I am using WP-CLI shell to quickly debug some code, but every time I run into a fatal exception (e.g. undefined constants/functions) the shell exits and I lose my shell session. Is there a way to prevent this?

wp> new DoesntExist();
Fatal error: Class 'DoesntExist' not found in phar:///usr/local/bin/wp/php/WP_CLI/REPL.php(37) : eval()'d code on line 1

Shell exits..

This is the default behavior of WP-CLI’s built-in PHP REPL. If you look at the wp shell documentation, it shows that you can also use the Boris or PsySH PHP REPLs.

The Boris REPL does not seem to be actively maintained; however the PsySH REPL has fairly recent maintenance, and it fixes the problem that you’re experiencing.

The easiest way to integrate PsySH with WP-CLI is to use the wp-cli-psysh plugin:

# Make sure WP-CLI is up to date
wp cli update

# Install the plugin
wp package install git@github.com:schlessera/wp-cli-psysh.git

After installing the plugin, running wp shell should show you a PsySH header that’s similar to this:

$ wp shell

Psy Shell v0.9.9 (PHP 7.3.1-1+ubuntu18.04.1+deb.sury.org+1 — cli) by Justin Hileman

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