Use Cython 3 implicit namespace package support

src/sage/algebras/quatalg/quaternion_algebra_cython.pyx

@@ -35,7 +35,7 @@ from sage.matrix.matrix_space import MatrixSpace
 from sage.matrix.matrix_integer_dense cimport Matrix_integer_dense
 from sage.matrix.matrix_rational_dense cimport Matrix_rational_dense
 
-from .quaternion_algebra_element cimport QuaternionAlgebraElement_rational_field
+from sage.algebras.quatalg.quaternion_algebra_element cimport QuaternionAlgebraElement_rational_field
 
 from sage.libs.gmp.mpz cimport mpz_t, mpz_lcm, mpz_init, mpz_set, mpz_clear, mpz_init_set, mpz_mul, mpz_fdiv_q, mpz_cmp_si
 

src/sage/arith/power.pyx

@@ -17,7 +17,7 @@ square-and-multiply algorithm.
 
 from cysignals.signals cimport sig_check
 
-from .long cimport integer_check_long
+from sage.arith.long cimport integer_check_long
 
 
 cpdef generic_power(a, n) noexcept:

src/sage/categories/action.pxd

@@ -1,7 +1,7 @@
 from sage.structure.element cimport Element
-from .morphism cimport Morphism
-from .map cimport Map
-from .functor cimport Functor
+from sage.categories.morphism cimport Morphism
+from sage.categories.map cimport Map
+from sage.categories.functor cimport Functor
 
 cdef class Action(Functor):
     cdef readonly G

src/sage/categories/action.pyx

@@ -56,13 +56,13 @@ AUTHOR:
 
 from cpython.tuple cimport PyTuple_GET_ITEM
 
-from .functor cimport Functor
-from .morphism cimport Morphism
-from .map cimport Map
+from sage.categories.functor cimport Functor
+from sage.categories.morphism cimport Morphism
+from sage.categories.map cimport Map
 from sage.structure.element cimport parent
 from sage.structure.parent cimport Parent
 
-from . import homset
+from sage.categories import homset
 from weakref import ref
 
 
@@ -91,7 +91,7 @@ cdef class Action(Functor):
       :class:`Action` itself, but other classes may use it
     """
     def __init__(self, G, S, is_left=True, op=None):
-        from .groupoid import Groupoid
+        from sage.categories.groupoid import Groupoid
         Functor.__init__(self, Groupoid(G), category(S))
         self.G = G
         self.US = ref(S)

src/sage/categories/functor.pyx

@@ -33,7 +33,7 @@ AUTHORS:
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-from . import category
+from sage.categories import category
 
 
 def _Functor_unpickle(Cl, D, domain, codomain):

src/sage/categories/map.pyx

@@ -21,7 +21,7 @@ AUTHORS:
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-from . import homset
+from sage.categories import homset
 import weakref
 from sage.ext.stdsage cimport HAS_DICTIONARY
 from sage.arith.power cimport generic_power

src/sage/categories/morphism.pxd

@@ -1,5 +1,5 @@
 from sage.structure.element cimport Element
-from .map cimport Map
+from sage.categories.map cimport Map
 
 
 cdef class Morphism(Map):

src/sage/categories/morphism.pyx

@@ -467,7 +467,7 @@ cdef class CallMorphism(Morphism):
 cdef class IdentityMorphism(Morphism):
 
     def __init__(self, parent):
-        from .homset import Homset, Hom
+        from sage.categories.homset import Homset, Hom
         if not isinstance(parent, Homset):
             parent = Hom(parent, parent)
         Morphism.__init__(self, parent)

src/sage/cpython/debug.pyx

@@ -21,7 +21,7 @@ cdef extern from "Python.h":
 cdef extern from "sage/cpython/debugimpl.c":
     void _type_debug(PyTypeObject*)
 
-from .getattr cimport AttributeErrorMessage
+from sage.cpython.getattr cimport AttributeErrorMessage
 
 
 # Determine subtype_traverse, subtype_clear, subtype_dealloc functions

src/sage/cpython/getattr.pyx

@@ -4,7 +4,7 @@ Variants of getattr()
 
 from cpython.object cimport PyObject, PyTypeObject, Py_TYPE, descrgetfunc
 
-from .string cimport bytes_to_str
+from sage.cpython.string cimport bytes_to_str
 
 cdef extern from "Python.h":
     r"""

src/sage/cpython/wrapperdescr.pyx

@@ -30,7 +30,7 @@ Pure Python classes have normal methods, not slot wrappers::
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-from .string import bytes_to_str
+from sage.cpython.string import bytes_to_str
 
 
 def wrapperdescr_call(slotwrapper, self, *args, **kwds):

src/sage/data_structures/bitset.pxd

@@ -7,7 +7,7 @@
 #                  http://www.gnu.org/licenses/
 #*****************************************************************************
 
-from .bitset_base cimport bitset_t
+from sage.data_structures.bitset_base cimport bitset_t
 
 # Python layer over bitset_t
 cdef class FrozenBitset:

src/sage/data_structures/bitset.pyx

@@ -31,7 +31,7 @@ linear in ``capacity``.
 #                  http://www.gnu.org/licenses/
 #*****************************************************************************
 
-from .bitset_base cimport *
+from sage.data_structures.bitset_base cimport *
 from cpython.object cimport Py_LT, Py_LE, Py_EQ, Py_NE, Py_GT, Py_GE
 
 

src/sage/matrix/matrix_mod2_dense.pxd

@@ -1,4 +1,4 @@
-from .matrix_dense cimport Matrix_dense
+from sage.matrix.matrix_dense cimport Matrix_dense
 from sage.libs.m4ri cimport *
 
 cdef class Matrix_mod2_dense(Matrix_dense):

src/sage/matrix/matrix_sparse.pxd

@@ -1,4 +1,4 @@
-from .matrix cimport Matrix
+from sage.matrix.matrix cimport Matrix
 
 cdef class Matrix_sparse(Matrix):
     pass

src/sage/misc/cachefunc.pxd

@@ -1,4 +1,4 @@
-from .function_mangling cimport ArgumentFixer
+from sage.misc.function_mangling cimport ArgumentFixer
 
 cpdef dict_key(o) noexcept
 cpdef cache_key(o) noexcept

src/sage/misc/lazy_import.pyx

@@ -66,7 +66,7 @@ import os
 import pickle
 from warnings import warn
 import inspect
-from . import sageinspect
+from sage.misc import sageinspect
 
 
 # LazyImport.__repr__ uses try... except FeatureNotPresentError.
@@ -1137,7 +1137,7 @@ def save_cache_file():
         sage: sage.misc.lazy_import.save_cache_file()
     """
     from sage.misc.temporary_file import atomic_write
-    from .lazy_import_cache import get_cache_file
+    from sage.misc.lazy_import_cache import get_cache_file
 
     global star_imports
     if star_imports is None:
@@ -1180,7 +1180,7 @@ def get_star_imports(module_name):
     """
     global star_imports
     if star_imports is None:
-        from .lazy_import_cache import get_cache_file
+        from sage.misc.lazy_import_cache import get_cache_file
         star_imports = {}
         try:
             with open(get_cache_file(), "rb") as cache_file:

src/sage/misc/package_dir.py

@@ -203,15 +203,19 @@ def cython_namespace_package_support():
 
     See https://github.com/cython/cython/issues/2918#issuecomment-991799049
     """
-    import Cython.Build.Dependencies
-    import Cython.Build.Cythonize
-    import Cython.Utils
-    orig_is_package_dir = Cython.Utils.is_package_dir
-    Cython.Utils.is_package_dir = Cython.Build.Cythonize.is_package_dir = Cython.Build.Dependencies.is_package_dir = Cython.Utils.cached_function(is_package_or_sage_namespace_package_dir)
-    try:
+    from Cython import __version__
+    if __version__[0] >= '3':
         yield
-    finally:
-        Cython.Utils.is_package_dir = Cython.Build.Cythonize.is_package_dir = Cython.Build.Dependencies.is_package_dir = orig_is_package_dir
+    else:
+        import Cython.Build.Dependencies
+        import Cython.Build.Cythonize
+        import Cython.Utils
+        orig_is_package_dir = Cython.Utils.is_package_dir
+        Cython.Utils.is_package_dir = Cython.Build.Cythonize.is_package_dir = Cython.Build.Dependencies.is_package_dir = Cython.Utils.cached_function(is_package_or_sage_namespace_package_dir)
+        try:
+            yield
+        finally:
+            Cython.Utils.is_package_dir = Cython.Build.Cythonize.is_package_dir = Cython.Build.Dependencies.is_package_dir = orig_is_package_dir
 
 
 def walk_packages(path=None, prefix='', onerror=None):

src/sage/misc/persist.pyx

@@ -42,7 +42,7 @@ import bz2
 comp = zlib
 comp_other = bz2
 
-from .sage_unittest import TestSuite
+from sage.misc.sage_unittest import TestSuite
 
 
 # We define two global dictionaries `already_pickled` and
@@ -1237,7 +1237,7 @@ def db(name):
 
     The database directory is ``$HOME/.sage/db``.
     """
-    from .misc import SAGE_DB
+    from sage.misc.misc import SAGE_DB
     return load('%s/%s'%(SAGE_DB,name))
 
 
@@ -1250,5 +1250,5 @@ def db_save(x, name=None):
     try:
         x.db(name)
     except AttributeError:
-        from .misc import SAGE_DB
+        from sage.misc.misc import SAGE_DB
         save(x, '%s/%s'%(SAGE_DB,name))

src/sage/misc/sage_timeit_class.pyx

@@ -6,7 +6,7 @@ The ``timeit`` command
 This uses the function :func:`~sage.misc.sage_timeit.sage_timeit`.
 """
 
-from . import sage_timeit
+from sage.misc import sage_timeit
 
 
 class SageTimeit:

src/sage/modular/modsym/heilbronn.pyx

@@ -34,11 +34,11 @@ cdef extern from "<math.h>":
     float roundf(float x)
 
 cimport sage.modular.modsym.p1list as p1list
-from . import p1list
+from sage.modular.modsym import p1list
 cdef p1list.export export
 export = p1list.export()
 
-from .apply cimport Apply
+from sage.modular.modsym.apply cimport Apply
 cdef Apply PolyApply= Apply()
 
 from sage.matrix.matrix_rational_dense cimport Matrix_rational_dense

src/sage/modular/pollack_stevens/dist.pyx

@@ -44,7 +44,7 @@ from sage.rings.infinity import Infinity
 
 #from sage.libs.flint.ulong_extras cimport *
 
-from .sigma0 import Sigma0
+from sage.modular.pollack_stevens.sigma0 import Sigma0
 
 cdef long overflow = 1 << (4 * sizeof(long) - 1)
 cdef long underflow = -overflow

src/sage/modules/vector_mod2_dense.pxd

@@ -1,4 +1,4 @@
-from .free_module_element cimport FreeModuleElement
+from sage.modules.free_module_element cimport FreeModuleElement
 from sage.libs.m4ri cimport mzd_t
 
 

src/sage/rings/abc.pxd

@@ -1,4 +1,4 @@
-from .ring cimport CommutativeRing, Field
+from sage.rings.ring cimport CommutativeRing, Field
 
 cdef class RealField(Field):
 

src/sage/rings/complex_conversion.pyx

@@ -1,5 +1,5 @@
-from .complex_double cimport ComplexDoubleElement
-from .complex_mpfr cimport ComplexNumber
+from sage.rings.complex_double cimport ComplexDoubleElement
+from sage.rings.complex_mpfr cimport ComplexNumber
 from sage.libs.mpfr cimport mpfr_get_d, MPFR_RNDN
 from sage.libs.gsl.complex cimport GSL_SET_COMPLEX