using an old attachment to make a git branch (lazy import checks)

src/sage/all.py

@@ -101,7 +101,7 @@
 from sage.algebras.all   import *
 from sage.modular.all    import *
 from sage.sat.all        import *
-from sage.schemes.all    import *
+lazy_import("sage.schemes.all", "*", overwrite=False)
 from sage.graphs.all     import *
 from sage.groups.all     import *
 from sage.arith.power    import generic_power as power
@@ -263,6 +263,7 @@ def quit_sage(verbose=True):
 
 # Cache the contents of star imports.
 sage.misc.lazy_import.save_cache_file()
+sage.misc.lazy_import._sage_all_import_done = True
 
 
 ### Debugging for Singular, see trac #10903
@@ -319,6 +320,7 @@ def _write_started_file():
 # From now on it is ok to resolve lazy imports
 sage.misc.lazy_import.finish_startup()
 
+
 def sage_globals():
     r"""
     Return the Sage namespace.

src/sage/misc/lazy_import.pyx

@@ -1138,7 +1138,7 @@ def get_star_imports(module_name):
         [...]
         sage: os.remove(cache_file)
     """
-    global star_imports
+    global star_imports, _sage_all_import_done
     if star_imports is None:
         star_imports = {}
         try:
@@ -1152,14 +1152,44 @@ def get_star_imports(module_name):
     try:
         return star_imports[module_name]
     except KeyError:
+        all_done = sage_all_import_done
+        _sage_all_import_done = True  # so that checks pass
         module = __import__(module_name, {}, {}, ["*"])
+        _sage_all_import_done = all_done
         if hasattr(module, "__all__"):
             all = module.__all__
         else:
             all = [key for key in dir(module) if key[0] != "_"]
         star_imports[module_name] = all
         return all
 
+# Utility functions for asserting that things stay lazily imported.
+
+
+_sage_all_import_done = False
+
+
+def check_lazy(module_name=None):
+    """
+    Used to assert lazily imported modules do not actually get imported
+    during the import of sage.all is done.
+
+    TESTS::
+
+        sage: from sage.misc.lazy_import import check_lazy
+        sage: check_lazy("foo")
+        True
+        sage: sage.misc.lazy_import._sage_all_import_done = False
+        sage: check_lazy("foo")
+        False
+        sage: sage.misc.lazy_import._sage_all_import_done = True
+        sage: check_lazy("foo")
+        True
+    """
+    if module_name is None:
+        module_name = inspect.currentframe().f_globals['__name__']
+    return _sage_all_import_done
+
 
 # Add support for _instancedoc_
 from sage.docs.instancedoc import instancedoc

src/sage/schemes/all.py

@@ -20,6 +20,8 @@
 #
 #                  http://www.gnu.org/licenses/
 #*****************************************************************************
+import sage.misc.lazy_import
+assert sage.misc.lazy_import.check_lazy()
 
 from .jacobians.all import *