Tab completion triggers "bad pattern: (utf|UTF)(-|)8" error in _p9k_on_expand

[rcdailey]

Bug Report

Problem

During tab completion, Powerlevel10k's _p9k_on_expand function continuously spams the following error pattern:

_p9k_on_expand:7: bad pattern: (utf|UTF)(-|)8
git commit
_p9k_on_expand:7: bad pattern: (utf|UTF)(-|)8
git commit
_p9k_on_expand:7: bad pattern: (utf|UTF)(-|)8
git commit

This creates an infinite loop of error messages that makes tab completion completely unusable. Ctrl+C is unresponsive, requiring the terminal window to be closed and reopened.

Root Cause Analysis

The issue stems from a malformed pattern in the __p9k_intro_locale variable. When running typeset | grep -i utf, the following problematic pattern is visible:

readonly __p9k_intro_locale='[[ $langinfo[CODESET] != (utf|UTF)(-|)8 ]] && _p9k_init_locale && { [[ -n $LC_ALL ]] && local LC_ALL=$__p9k_locale || local LC_CTYPE=$__p9k_locale }'

The pattern (utf|UTF)(-|)8 appears to be malformed for zsh pattern matching, causing zsh to report "bad pattern" errors when it's evaluated during completion expansion.

Reproduction Steps

1. Install Powerlevel10k with any completion system (fzf-tab, standard zsh completion, etc.)
2. Type git commit (with a space)
3. Press TAB for completion
4. Observe continuous error spam that cannot be interrupted with Ctrl+C

Environment

• OS: macOS 14.5 (Darwin 24.5.0)
• Zsh version: 5.9
• Powerlevel10k version: Latest (commit 36f3045)
• Terminal: iTerm2
• Locale: All UTF-8 (LANG=en_US.UTF-8, LC_ALL=en_US.UTF-8, LC_CTYPE=en_US.UTF-8)

Expected Behavior

Tab completion should work without generating error messages.

Actual Behavior

Tab completion triggers an infinite loop of "bad pattern" error messages from _p9k_on_expand:7 that cannot be interrupted, requiring terminal restart.

Workaround

The issue can be worked around by wrapping the _p9k_on_expand function to suppress stderr:

if (( $+functions[_p9k_on_expand] )); then
    functions[_p9k_on_expand_orig]=$functions[_p9k_on_expand]
    _p9k_on_expand() {
        { _p9k_on_expand_orig "$@" } 2>/dev/null
    }
fi

Additional Notes

• The error persists even with proper UTF-8 locale configuration
• The issue occurs regardless of the completion system used (tested with fzf-tab disabled)
• The pattern appears to be hardcoded in Powerlevel10k's locale detection logic

This seems to be a regex pattern that needs proper escaping for zsh pattern matching.

[romkatv]

What's the minimal .zshrc that reproduces the problem?

[rcdailey]

The minimal .zshrc that reproduces the problem:

# Enable Powerlevel10k instant prompt
if [[ -r "${XDG_CACHE_HOME:-$HOME/.cache}/p10k-instant-prompt-${(%):-%n}.zsh" ]]; then
  source "${XDG_CACHE_HOME:-$HOME/.cache}/p10k-instant-prompt-${(%):-%n}.zsh"
fi

# Load zinit
source ~/.local/share/zinit/zinit.git/zinit.zsh

# Load Powerlevel10k
zinit ice depth=1
zinit load romkatv/powerlevel10k

# Basic completion setup
autoload -Uz compinit
compinit

# Load fzf and fzf-tab
zinit ice silent
zinit load "junegunn/fzf"
zinit ice silent  
zinit load "Aloxaf/fzf-tab"

# Enable fzf-tab
enable-fzf-tab

# Load p10k config
[[ ! -f ~/.p10k.zsh ]] || source ~/.p10k.zsh

# Finalize Powerlevel10k
p10k finalize

Reproduction steps:

1. Use the above .zshrc
2. Open new terminal
3. Type git commit (with trailing space)
4. Press TAB

This triggers the continuous _p9k_on_expand:7: bad pattern: (utf|UTF)(-|)8 error spam.

Key finding: The issue requires fzf-tab to be present. Without fzf-tab, tab completion works normally with just Powerlevel10k + compinit.