Script to compile and format *.yaml.jinja files in Home Assistant config directory (Including systemd service)

ha_compile_jinja.service

[Unit]
Description=Compile Jinja templates to YAML in Home Assistant config directory
After=network.target
StartLimitIntervalSec=0

[Service]
Type=simple
Restart=always
RestartSec=3
ExecStart=/opt/ha_compile_jinja.sh

[Install]
WantedBy=multi-user.target

ha_compile_jinja.sh

#!/bin/bash
set -euo pipefail
HASS_CONFIG_DIR="/usr/share/hassio/homeassistant"

if ! type jinja > /dev/null 2>&1; then
  echo "jinja-cli must be installed: pip install jinja-cli (https://pypi.org/project/jinja-cli/)"
  sleep 1
  exit 1
fi
if ! type prettier > /dev/null 2>&1; then
  echo "Prettier must be installed: apt-get install nodejs npm && npm install -g prettier"
  sleep 1
  exit 1
fi

remove() {
  OUTPUT_FILE="$1${2/.jinja}"
  echo "$1$2 deleted, removing: $OUTPUT_FILE"
  rm -f "$OUTPUT_FILE"
}

compile() {
  echo "$1$2 changed, compiling to: $1${2/.jinja}"
  ERROR_LOG_FILE="$1$2.errors.log"
  OUTPUT_FILE="$1${2/.jinja}"
  echo "# DO NOT EDIT: Generated from: $2 ($0)" > "$OUTPUT_FILE"
  # Log any errors to an .errors.log file, delete if successful
  if jinja "$1$2" >> "$OUTPUT_FILE" 2> "$ERROR_LOG_FILE"; then
    (rm -f "$ERROR_LOG_FILE" || true)
    echo "Formatting $OUTPUT_FILE with Prettier..."
    prettier --write "$OUTPUT_FILE" --loglevel warn || true
  else
    (rm -f "$OUTPUT_FILE" || true)
    echo "Error compiling $1$2!"
    if [ -f "$ERROR_LOG_FILE" ]; then cat "$ERROR_LOG_FILE" >&2; fi
  fi
}

echo "Compiling Jinja templates to YAML: $HASS_CONFIG_DIR/**/*.yaml.jinja"
inotifywait -q -m -r -e modify,delete,create,move "$HASS_CONFIG_DIR" | while read DIRECTORY EVENT FILE; do
  if [[ "$FILE" != *.yaml.jinja ]]; then continue; fi

  case $EVENT in
    MODIFY*)
      compile "$DIRECTORY" "$FILE";;
    CREATE*)
      compile "$DIRECTORY" "$FILE";;
    MOVED_TO*)
      compile "$DIRECTORY" "$FILE";;
    DELETE*)
      remove "$DIRECTORY" "$FILE";;
    MOVED_FROM*)
      remove "$DIRECTORY" "$FILE";;
  esac
  sleep 0.5
done

sleep 1

I've wrapped this up as an addon here https://github.com/tonyroberts/hassio-jinja2config

Thanks @ndbroadbent, this was exactly what I was looking for to simplify some complex config!