Slow shell initialization for Bash because of trap DEBUG instruction

[RickWong]

Added these lines to my .bashrc (btw macOS uses .profile instead) and afterwards my shell init took 2+ seconds :

eval "$(/opt/homebrew/bin/rv shell init bash)"
eval "$(/opt/homebrew/bin/rv shell completions bash)"

Found the culprit to be the first line, it's caused by the trap instruction inside:

_rv_autoload_hook() {
    eval "$(/opt/homebrew/bin/rv shell env bash)"
}
trap '[[ "$BASH_COMMAND" != "$PROMPT_COMMAND" ]] && _rv_autoload_hook' DEBUG
_rv_autoload_hook

By inlining eval "$(/opt/homebrew/bin/rv shell env bash)" directly in my .bashrc the slowness goes away. I'm not entirely sure what the trap instruction is used for.

[deivid-rodriguez]

Hi @RickWong, thanks for the report!

I just added an echo to the _rv_autoload_hook function and I can confirm it is running too many times also for me when my shell profile is loaded.

The idea of this hook is that your environment is automatically reloaded when you change a .ruby-version file.

I copied this approach originally from chruby, but I just tried mise's approach, and it does seem to work better.

I think we can change to that, I'll work on it 👍.

[deivid-rodriguez]

@RickWong Just curious, are you using rv 0.5.3? There's a fix in that release that could explain the performance issue (in combination with loading shell integration too many times like we do now).

[RickWong]

@deivid-rodriguez Yes I'm on rv 0.5.3.

[deivid-rodriguez]

@RickWong Would you be able to try if the approach in #647 fixes the problem for you?

[RickWong]

@deivid-rodriguez Yup, with #647 the overhead seems gone.