Add support for env var in metadata files

.gitignore

 /output
+/.env
 
 __pycache__
 

boop.py

 
 from jinja2 import Environment, PackageLoader, select_autoescape
 from PIL import Image, ExifTags
+from dotenv import load_dotenv
 
 from configuration import SITE_TITLE, SITE_AUTHOR, SITE_AUTHOR_WEBSITE, THEME
 
 
+# Load env var from .env file
+load_dotenv(dotenv_path=".env")
+
+
 PICTURES_DIR_NAME = "photos"
 OUTPUT_DIR_NAME = "output"
 
+# Configure YAML to accept environment variables in metadata files
+# Based on https://stackoverflow.com/a/27232341 solution
+pattern = re.compile(r"^ENV\[\'(.*)\'\]$")
+yaml.add_implicit_resolver("!pathex", pattern)
+
+
+def pathex_constructor(loader, node):
+    value = loader.construct_scalar(node)
+    env_var, = pattern.match(value).groups()
+    return os.getenv(env_var)
+
+
+yaml.add_constructor("!pathex", pathex_constructor)
+
 
 def list_galleries_in(path):
     gallery_dirs = [f for f in os.scandir(path) if f.is_dir()]

photos/2018-06_Moucheraclette/metadata.yml

 ---
-name: "9. Moucheraclette"
+name: "Moucheraclette"
 cover: "DSC04034.JPG"
+password: ENV['BOOP_MOUCHERACLETTE_PASSWORD']

requirements.txt

 Jinja2
 Pillow
 pyyaml
+python-dotenv