add plugin template and bootloader

isbnlib/__init__.py

@@ -26,6 +26,9 @@ def emit(self, record):
 # configuration
 from . import config  # <-- first import
 
+# plugin bootloader
+from . import _bootloader
+
 # main modules
 from ._core import (is_isbn10, is_isbn13, to_isbn10, to_isbn13, clean,
                     canonical, notisbn, get_isbnlike, get_canonical_isbn,

isbnlib/_bootloader.py

@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+"""Bootloader for plugins."""
+
+# <--- NOTE: THIS CODE RUNS ON IMPORT! --->
+
+from pkg_resources import iter_entry_points
+
+from . import registry
+
+# get plugins from entry_points
+try:  # pragma: no cover
+    for entry in iter_entry_points(group='isbnlib.metadata'):
+        registry.add_service(entry.name, entry.load())
+except:  # pragma: no cover
+    pass
+
+# get formatters from entry_points
+try:  # pragma: no cover
+    for entry in iter_entry_points(group='isbnlib.formatters'):
+        registry.add_bibformatter(entry.name, entry.load())
+except:  # pragma: no cover
+    pass