Trying rule missing_space_before_subcommand taking so long

[auspic7]

The output of thefuck --version (something like The Fuck 3.1 using Python 3.5.0 and Bash 4.4.12(1)-release):

The Fuck 3.29 using Python 3.8.2 and ZSH 5.8

Your system (Debian 7, ArchLinux, Windows, etc.):

ubuntu 20.04 on wsl2

How to reproduce the bug:

env THEFUCK_DEBUG=true thefuck test

The output of The Fuck with THEFUCK_DEBUG=true exported (typically execute export THEFUCK_DEBUG=true in your shell before The Fuck):

DEBUG: Trying rule: missing_space_before_subcommand; took: 0:00:08.341279
No fucks given

Anything else you think is relevant:

I have no idea why this taking so long. anyone else having this problem?

[dvjn]

This rule is using get_all_executables in which it scans all the directories in PATH for possible executables AFAIK, normally it shouldn't be a problem, but in WSL the path of your host Windows OS gets concatenated with the Ubuntu's path. So it has to scan more paths for executable (to find the correct one), hence it takes longer.

Could you try out running and timing a non-existent command, and check if that takes a long time to execute too?
Something like:

$ time abcd

[auspic7]

$ time abcd 
zsh: command not found: abcd
abcd  0.00s user 0.01s system 18% cpu 0.049 total

non-existent command won't take a long time.

by the way, env THEFUCK_DEBUG=true thefuck abcd will still take longer time since Trying rule: no_command takes a lot.

DEBUG: Trying rule: no_command; took: 0:00:08.681820

[dvjn]

I was not able to find a proper reason as to is why this happening. I think thefuck is just unoptimized at many places which are aggregating to make it slow.

I think, let's try a cProfile

THEFUCK_DEBUG=true python -m cProfile $(which thefuck) zzzzzz

[pdavies]

I think this might be a dupe of #1036. On WSL, usually no_command runs slowly for me, but I'm sure while testing that, once or twice I saw missing_space_before_subcommand running slowly instead. At a guess, memoization of get_all_executables means that whoever hits it first pays the performance penalty, and occasionally missing_space_before_subcommand gets there first.

The fix, as with #1036 currently, is to set excluded_search_path_prefixes. In my testing, /mnt/c/WINDOWS (and subdirectories) was overwhelmingly the culprit. Adding that has resulted in a massive speedup.

[scorphus]

Duplicate of #1036