WP_CLI_CACHE_EXPIRY=0 and WP_CLI_CACHE_MAX_SIZE=0 fall back to the defaults #6452

Bug summary

WP_CLI::get_cache() reads the two cache limits like this on main (source):

$ttl      = (int) Utils\get_env_or_config( 'WP_CLI_CACHE_EXPIRY' ) ? : 15552000;
$max_size = (int) Utils\get_env_or_config( 'WP_CLI_CACHE_MAX_SIZE' ) ? : 314572800;

0 is falsy, so WP_CLI_CACHE_EXPIRY=0 and WP_CLI_CACHE_MAX_SIZE=0 become the defaults of 180 days and 300 MB. The same happens when the values are set under env: in wp-cli.yml. WP-CLI 2.12.0 reads getenv( 'WP_CLI_CACHE_EXPIRY' ) ? : 15552000 (no cast), and the string '0' is just as falsy there.

FileCache itself treats 0 as no limit: clean() only expires files when $ttl > 0 (L237) and only trims the cache when $max_size > 0 (L255). A negative value already reaches FileCache and turns the limit off, so 0 is the one value that cannot.

Steps to reproduce

mkdir cache
export WP_CLI_CACHE_DIR="$PWD/cache"
touch -t 202501010000 cache/old.bin
printf '<?php WP_CLI::get_cache()->clean();\n' > clean.php
WP_CLI_CACHE_EXPIRY=0 wp --require=clean.php cli version
ls cache

old.bin is deleted, because it is older than the default 180 days. With WP_CLI_CACHE_EXPIRY=-1 it is kept.

Expected

0 reaches FileCache as 0, so the cache expiry or the size limit is turned off.

Environment

• WP-CLI 2.12.0 (the steps above) and main at aafc2a8 (the same steps, run from a checkout), PHP 8.5, macOS

Possible solution

Fall back to the default only when the value cast to an integer is 0 and the value is not a number. A number that casts to 0, such as 0 or 0.5, then turns the limit off. Empty and non-numeric values keep the defaults, and values that cast to a non-zero number are read as before. I have a fix with tests and will open a PR.