With Fisher:
fisher install zuisong/pnpm-fish-completion
With fundle:
# Add this to your ~/.config/fish/config.fish
fundle plugin zuisong/pnpm-fish-completion
curl -Lo ~/.config/fish/completions/pnpm.fish \
--create-dirs \
https://raw.githubusercontent.com/zuisong/pnpm-fish-completion/main/completions/pnpm.fish