[PyROOT] Actively wildcard imports from ROOT and its submodules

With this commit, the user will get an `ImportError` when trying to do
`from ROOT import *` or for example `from ROOT.RooFit import *`.

Before this commit, such commands were succeeding but without actually
importing anything, which might me confusing to the user because the
expect that everything from ROOT gets imported.

bindings/pyroot/pythonizations/python/ROOT/__init__.py

@@ -53,6 +53,20 @@
 else:
     import __builtin__ as builtins
 
+
+class _PoisonedDunderAll(object):
+    """Dummy class used to trigger an ImportError on wildcard imports if the
+    __all__attribute of a module is an instance of this class.
+    """
+
+    def __getitem__(self, _):
+        raise ImportError("Wildcard imports such as `from ROOT import *` are not possible in PyROOT")
+
+
+# Prevent `from ROOT import *` by setting the __all__ attribute to something
+# that will raise an ImportError on item retrieval.
+__all__ = _PoisonedDunderAll()
+
 _is_ipython = hasattr(builtins, "__IPYTHON__")
 
 # Configure ROOT facade module
@@ -127,7 +141,12 @@ def is_package(self, fullname: str) -> bool:
         return _lookup_root_module(fullname) is not None
 
     def create_module(self, spec: ModuleSpec):
-        return _lookup_root_module(spec.name)
+        out = _lookup_root_module(spec.name)
+        # Prevent wildcard import for the submodule by setting the __all__
+        # attribute to something that will raise an ImportError on item
+        # retrieval.
+        out.__all__ = _PoisonedDunderAll()
+        return out
 
     def exec_module(self, module):
         pass

bindings/pyroot/pythonizations/python/ROOT/_facade.py

@@ -82,9 +82,8 @@ def __init__(self, module, is_ipython):
         types.ModuleType.__init__(self, module.__name__)
 
         self.module = module
-        # Importing all will be customised later
-        self.module.__all__ = []
 
+        self.__all__ = module.__all__
         self.__name__ = module.__name__
         self.__file__ = module.__file__
         self.__cached__ = module.__cached__