Allow disabled eager loading with EAGER_IMPORT=0

Author: stefanv

README.md

@@ -99,7 +99,7 @@ detail](https://scientific-python.org/specs/spec-0001/#type-checkers).
 
 With lazy loading, missing imports no longer fail upon loading the
 library. During development and testing, you can set the `EAGER_IMPORT`
-environment variable to disable lazy loading.
+environment variable to a value other than "0" to disable lazy loading.
 
 ### External libraries
 

src/lazy_loader/__init__.py

@@ -92,7 +92,8 @@ def __getattr__(name):
     def __dir__():
         return __all__.copy()
 
-    if os.environ.get("EAGER_IMPORT", ""):
+    eager_import = os.environ.get("EAGER_IMPORT", "") != "0"
+    if eager_import:
         for attr in set(attr_to_modules.keys()) | submodules:
             __getattr__(attr)