Zero-downtime mise upgrade

mise-safe-upgrade

#!/bin/sh

set -e

config=$HOME/.config/mise/config.toml

usage() {
    echo "Usage: $0 [-p config] [tool...]"
}

current_tools() {
    printf %s "$outdated" | jq -r \
        'to_entries[] | select(.value.current != null) | "\(.key)@\(.value.current)"'
}

latest_tools() {
    printf %s "$outdated" | jq -r \
        'to_entries[] | "\(.key)@\(.value.latest)"'
}

new_latest_tools() {
    latest_tools | while IFS= read -r spec; do
        tool=${spec%@*}
        version=${spec##*@}
        if ! mise ls --json --installed "$tool" |
            jq -e --arg version "$version" 'any(.[]; .version == $version)' >/dev/null; then
            printf '%s\n' "$spec"
        fi
    done
}

pin_current_paths() {
    [ -n "$current_specs" ] || return 0

    # shellcheck disable=SC2016,SC2086
    PATH=$(mise exec $current_specs -- sh -c 'printf %s "$PATH"')
    export PATH
}

cleanup_new_latest_tools() {
    [ -n "$new_latest_specs" ] || return 0

    # shellcheck disable=SC2086
    mise uninstall -y $new_latest_specs
}

while getopts "p:" opt; do
    case $opt in
        p)
            config=$OPTARG
            ;;
        \?)
            usage
            exit 1
            ;;
    esac
done

shift $((OPTIND - 1))

config=$(realpath "$config")
config_bak=${config%.toml}.bak.toml

if [ -f "$config_bak" ]; then
    echo "$config_bak exists; upgrade seems to be in progress."
    exit 1
fi

cd "$(dirname "$config")"

# Get outdated tools.
outdated=$(mise outdated --json "$@")
if [ "$outdated" = '{}' ]; then
    echo Nothing to upgrade.
    exit
fi

current_specs=$(current_tools)
latest_specs=$(latest_tools)

# Prefer currently installed tool bins while new versions are being installed.
pin_current_paths

new_latest_specs=$(new_latest_tools)

# Pin the tools to the currently installed versions while new versions are being installed.
cp -p "$config" "$config_bak"
if [ -n "$current_specs" ]; then
    # shellcheck disable=SC2086
    mise use --path "$config" $current_specs
fi

# Install the latest versions.  If this fails, remove any partial latest
# installs before restoring the config.
# shellcheck disable=SC2086
if mise install $latest_specs; then
    mv "$config_bak" "$config"
else
    ret=$?
    if cleanup_new_latest_tools; then
        mv "$config_bak" "$config"
    else
        echo "Upgrade cleanup failed; $config remains pinned to the previous versions." >&2
    fi
    exit "$ret"
fi