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diff --git a/docs/dev/xdebug.md b/docs/dev/xdebug.md new file mode 100644 index 00000000..be198cca --- /dev/null +++ b/docs/dev/xdebug.md @@ -0,0 +1,28 @@ +# Xdebug + +Composer restarts itself without Xdebug loaded, because Xdebug makes PHP +several times slower. Shirabe is written in Rust, where Xdebug does not exist, +but it invokes a PHP command for plugins, scripts and platform queries. +When Shirabe spawns a PHP worker, Xdebug is disabled as Composer does. + +The PHP worker is spawned with the `-d xdebug.mode=off` flag and the +`XDEBUG_MODE=off` environment variable. The way to disable Xdebug in Shirabe is +different from Composer: Composer restarts its own process with a temporary +INI file, where Xdebug extension is disabled. The difference probably does not +matter, both for users and for plugin authors. + +## Enable Xdebug in Shirabe's PHP worker + +It is the same as Composer: setting `COMPOSER_ALLOW_XDEBUG` to 1 makes Shirabe +leave Xdebug enabled. + +``` +$ COMPOSER_ALLOW_XDEBUG=1 shirabe install +``` + +## Xdebug 2 support + +Shirabe does not try to disable Xdebug version 2 because Xdebug 2 has no +`xdebug.mode` or `XDEBUG_MODE`, while Composer disables Xdebug 2 too. The +performance penalty seems to be small as Shirabe's CPU-heavy workloads are +written in Rust. |