Merge branch 'public/build/startupWarning' of git://trac.sagemath.org…

…/sage into public/refactoring/pytest

src/sage/all.py

@@ -345,10 +345,6 @@ def _write_started_file():
 # Sage startup).
 set_random_seed()
 
-
-# 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/all_cmdline.py

@@ -23,8 +23,9 @@
 
 sage_mode = 'cmdline'
 
-from sage.all import *
-from sage.calculus.predefined import x
-
-sage.misc.session.init()
+import sage.misc.startup_guard as startup_guard
 
+with startup_guard.startup():
+    from sage.all import *
+    from sage.calculus.predefined import x
+    sage.misc.session.init()

src/sage/misc/lazy_import.pyx

@@ -58,6 +58,7 @@ AUTHOR:
 cimport cython
 from cpython.object cimport PyObject_RichCompare
 from cpython.number cimport PyNumber_TrueDivide, PyNumber_Power, PyNumber_Index
+import sage.misc.startup_guard as startup_guard
 
 cdef extern from *:
     int likely(int) nogil  # Defined by Cython
@@ -76,66 +77,6 @@ cdef inline obj(x):
     else:
         return x
 
-
-# boolean to determine whether Sage is still starting up
-cdef bint startup_guard = True
-
-
-cpdef finish_startup():
-    """
-    This function must be called exactly once at the end of the Sage
-    import process
-
-    TESTS::
-
-        sage: from sage.misc.lazy_import import finish_startup
-        sage: finish_startup()
-        Traceback (most recent call last):
-        ...
-        AssertionError: finish_startup() must be called exactly once
-    """
-    global startup_guard
-    assert startup_guard, 'finish_startup() must be called exactly once'
-    startup_guard = False
-
-cpdef bint is_during_startup():
-    """
-    Return whether Sage is currently starting up.
-
-    OUTPUT:
-
-    Boolean
-
-    TESTS::
-
-        sage: from sage.misc.lazy_import import is_during_startup
-        sage: is_during_startup()
-        False
-    """
-    global startup_guard
-    return startup_guard
-
-cpdef test_fake_startup():
-    """
-    For testing purposes only.
-
-    Switch the startup lazy import guard back on.
-
-    EXAMPLES::
-
-        sage: sage.misc.lazy_import.test_fake_startup()
-        sage: from sage.misc.lazy_import import lazy_import
-        sage: lazy_import('sage.rings.all', 'ZZ', 'my_ZZ')
-        sage: my_ZZ(123)
-        Traceback (most recent call last):
-        ...
-        RuntimeError: resolving lazy import ZZ during startup
-        sage: sage.misc.lazy_import.finish_startup()
-    """
-    global startup_guard
-    startup_guard = True
-
-
 @cython.final
 cdef class LazyImport(object):
     """
@@ -216,9 +157,9 @@ cdef class LazyImport(object):
         if self._object is not None:
             return self._object
 
-        if startup_guard and not self._at_startup:
+        if startup_guard.IS_STARTUP and not self._at_startup:
             raise RuntimeError(f"resolving lazy import {self._name} during startup")
-        elif self._at_startup and not startup_guard:
+        elif self._at_startup and not startup_guard.IS_STARTUP:
             print('Option ``at_startup=True`` for lazy import {0} not needed anymore'.format(self._name))
         try:
             self._object = getattr(__import__(self._module, {}, {}, [self._name]), self._name)

src/sage/misc/startup_guard.py

@@ -0,0 +1,25 @@
+from contextlib import contextmanager
+
+IS_STARTUP: bool = False
+
+@contextmanager
+def startup():
+    """
+    Simple context manager to indicate whether Sage is currently starting,
+    e.g. importing `sage.all` etc.
+    
+    EXAMPLES::
+
+        sage: import sage.misc.startup_guard as startup_guard
+        sage: print(startup_guard.IS_STARTUP)
+        False
+        sage: with startup_guard.startup():
+        sage:     print(startup_guard.IS_STARTUP)
+        True
+        sage: print(startup_guard.IS_STARTUP)
+        False
+    """
+    global IS_STARTUP
+    IS_STARTUP = True
+    yield
+    IS_STARTUP = False