Catch exceptions in REPL to preserve session state on errors

[Copilot]

Plan: Add Exception Handling to Prevent Session Crashes ✅

• Understand the current REPL implementation in src/WP_CLI/Shell/REPL.php
• Wrap eval() calls with try-catch blocks to catch Throwable (includes both exceptions and errors)
• Display caught errors/exceptions to the user but continue the session
• Improve error format to show class and message (cleaner than full stack trace)
• Add Behat test to verify exception handling works correctly
• Fix test failures by using When I try instead of When I run for tests that expect STDERR
• Test the implementation manually
• Run code review and address feedback
• Run security checks
• All tests passing ✅

Summary

Successfully implemented exception handling in the WP-CLI shell REPL to prevent session crashes on errors. All tests now pass.

Changes Made:

• Modified src/WP_CLI/Shell/REPL.php to wrap both eval() calls with try-catch blocks
• Errors are caught and displayed to STDERR without crashing the session
• Clean error format: ErrorClass: error message
• Added 2 comprehensive Behat test scenarios to verify the fix
• Fixed tests to use When I try for scenarios that write to STDERR

Test Results:

• All 7 scenarios passing (35 steps)
• Linting, code style, and static analysis checks passing
• Security scan passing

Original prompt

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This section details on the original issue you should resolve

<issue_title>Catch exceptions to avoid restarting session</issue_title>
<issue_description>## Feature Request

• Yes, I reviewed the contribution guidelines.

Describe your use case and the problem you are facing

Making typos/etc often results in a fatal error, and the session crashes and has to be restarted. After restarting, I have to recreate any variables, includes, etc from scratch, without making any fatal errors. That often makes it just too frustrating to use.

> wp shell
wp> require 'foo.txt';
Warning: require(foo.txt): Failed to open stream: No such file or directory in phar:///usr/local/bin/wp/vendor/wp-cli/shell-command/src/WP_CLI/Shell/REPL.php(32) : eval()'d code on line 1
Fatal error: Uncaught Error: Failed opening required 'foo.txt' (include_path='.:/usr/local/Cellar/php/8.0.0_1/share/php/pear') in phar:///usr/local/bin/wp/vendor/wp-cli/shell-command/src/WP_CLI/Shell/REPL.php(32) : eval()'d code:1
Stack trace:
wp-cli/shell-command#0 phar:///usr/local/bin/wp/vendor/wp-cli/shell-command/src/WP_CLI/Shell/REPL.php(32): eval()
wp-cli/shell-command#1 phar:///usr/local/bin/wp/vendor/wp-cli/shell-command/src/Shell_Command.php(51): WP_CLI\Shell\REPL->start()
wp-cli/shell-command#2 [internal function]: Shell_Command->__invoke(Array, Array)
wp-cli/shell-command#3 phar:///usr/local/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Dispatcher/CommandFactory.php(98): call_user_func(Array, Array, Array)
wp-cli/shell-command#4 [internal function]: WP_CLI\Dispatcher\CommandFactory::WP_CLI\Dispatcher\{closure}(Array, Array)
wp-cli/shell-command#5 phar:///usr/local/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Dispatcher/Subcommand.php(451): call_user_func(Object(Closure), Array, Array)
wp-cli/shell-command#6 phar:///usr/local/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(371): WP_CLI\Dispatcher\Subcommand->invoke(Array, Array, Array)
wp-cli/shell-command#7 phar:///usr/local/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(394): WP_CLI\Runner->run_command(Array, Array)
wp-cli/shell-command#8 phar:///usr/local/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(1160): WP_CLI\Runner->run_command_and_exit()
wp-cli/shell-command#9 phar:///usr/local/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Bootstrap/LaunchRunner.php(23): WP_CLI\Runner->start()
wp-cli/shell-command#10 phar:///usr/local/bin/wp/vendor/wp-cli/wp-cli/php/bootstrap.php(74): WP_CLI\Bootstrap\LaunchRunner->process(Object(WP_CLI\Bootstrap\BootstrapState))
wp-cli/shell-command#11 phar:///usr/local/bin/wp/vendor/wp-cli/wp-cli/php/wp-cli.php(27): WP_CLI\bootstrap()
wp-cli/shell-command#12 phar:///usr/local/bin/wp/php/boot-phar.php(11): include('phar:///usr/loc...')
wp-cli/shell-command#13 /usr/local/bin/wp(4): include('phar:///usr/loc...')
wp-cli/shell-command#14 {main}
  thrown in phar:///usr/local/bin/wp/vendor/wp-cli/shell-command/src/WP_CLI/Shell/REPL.php(32) : eval()'d code on line 1
Error: There has been a critical error on this website.Learn more about debugging in WordPress. There has been a critical error on this website.

Describe the solution you'd like

PHP's REPL is able to catch fatals and continue running:

php > $foo = 'stuff';
php > echo $foo;
stuff
php > require 'foo.txt';

Warning: require(foo.txt): Failed to open stream: No such file or directory in php shell code on line 1

Warning: Uncaught Error: Failed opening required 'foo.txt' (include_path='.:/usr/local/Cellar/php/8.0.0_1/share/php/pear') in php shell code:1
Stack trace:
wp-cli/shell-command#0 {main}
  thrown in php shell code on line 1
php > echo $foo;
stuff

Is that possible for wp shell ?</issue_description>

Comments on the Issue (you are @copilot in this section)

@schlessera Yes, this is something that annoys me as well. I guess it shouldn't;t be too hard to add an exception handler clause to the internal loop...?

• Fixes Catch exceptions to avoid restarting session #50

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