BUG: sparse: raise error for array classes, document/test old behavior (

#20490)

* (feat): raise errory for array classes, document/test old behavior

* (fix): lint issues

* Apply suggestions from code review

Co-authored-by: Dan Schult <dschult@colgate.edu>

* (fix): string overrun

* (fix): more string overrun issues

* Update _bsr.py

* (refactor): check for singleton in `_spbase`

---------

Co-authored-by: Dan Schult <dschult@colgate.edu>
Co-authored-by: CJ Carey <perimosocordiae@gmail.com>

scipy/sparse/_base.py

@@ -110,11 +110,15 @@ def _lil_container(self):
         from ._lil import lil_array
         return lil_array
 
-    def __init__(self, maxprint=MAXPRINT):
+    def __init__(self, arg1, maxprint=MAXPRINT):
         self._shape = None
         if self.__class__.__name__ == '_spbase':
             raise ValueError("This class is not intended"
                              " to be instantiated directly.")
+        if isinstance(self, sparray) and np.isscalar(arg1):
+            raise ValueError(
+                "scipy sparse array classes do not support instantiation from a scalar"
+            )
         self.maxprint = maxprint
 
     @property
@@ -1319,7 +1323,7 @@ def _get_index_dtype(self, arrays=(), maxval=None, check_contents=False):
 
 class sparray:
     """A namespace class to separate sparray from spmatrix"""
-    pass
+
 
 sparray.__doc__ = _spbase.__doc__
 

scipy/sparse/_bsr.py

@@ -25,7 +25,7 @@ class _bsr_base(_cs_matrix, _minmax_mixin):
     _format = 'bsr'
 
     def __init__(self, arg1, shape=None, dtype=None, copy=False, blocksize=None):
-        _data_matrix.__init__(self)
+        _data_matrix.__init__(self, arg1)
 
         if issparse(arg1):
             if arg1.format == self.format and copy:
@@ -94,8 +94,10 @@ def __init__(self, arg1, shape=None, dtype=None, copy=False, blocksize=None):
                     if not isshape(blocksize):
                         raise ValueError(f'invalid blocksize={blocksize}')
                     if tuple(blocksize) != self.data.shape[1:]:
-                        raise ValueError('mismatching blocksize={} vs {}'.format(
-                            blocksize, self.data.shape[1:]))
+                        raise ValueError(
+                            f'mismatching blocksize={blocksize}'
+                            f' vs {self.data.shape[1:]}'
+                        )
             else:
                 raise ValueError('unrecognized bsr_array constructor usage')
         else:

scipy/sparse/_compressed.py

@@ -25,7 +25,7 @@ class _cs_matrix(_data_matrix, _minmax_mixin, IndexMixin):
     """
 
     def __init__(self, arg1, shape=None, dtype=None, copy=False):
-        _data_matrix.__init__(self)
+        _data_matrix.__init__(self, arg1)
         is_array = isinstance(self, sparray)
 
         if issparse(arg1):

scipy/sparse/_coo.py

@@ -25,7 +25,7 @@ class _coo_base(_data_matrix, _minmax_mixin):
     _format = 'coo'
 
     def __init__(self, arg1, shape=None, dtype=None, copy=False):
-        _data_matrix.__init__(self)
+        _data_matrix.__init__(self, arg1)
         is_array = isinstance(self, sparray)
         if not copy:
             copy = copy_if_needed

scipy/sparse/_data.py

@@ -18,8 +18,8 @@
 # TODO implement all relevant operations
 # use .data.__methods__() instead of /=, *=, etc.
 class _data_matrix(_spbase):
-    def __init__(self):
-        _spbase.__init__(self)
+    def __init__(self, arg1):
+        _spbase.__init__(self, arg1)
 
     @property
     def dtype(self):

scipy/sparse/_dia.py

@@ -20,7 +20,7 @@ class _dia_base(_data_matrix):
     _format = 'dia'
 
     def __init__(self, arg1, shape=None, dtype=None, copy=False):
-        _data_matrix.__init__(self)
+        _data_matrix.__init__(self, arg1)
 
         if issparse(arg1):
             if arg1.format == "dia":

scipy/sparse/_dok.py

@@ -19,7 +19,7 @@ class _dok_base(_spbase, IndexMixin, dict):
     _format = 'dok'
 
     def __init__(self, arg1, shape=None, dtype=None, copy=False):
-        _spbase.__init__(self)
+        _spbase.__init__(self, arg1)
 
         is_array = isinstance(self, sparray)
         if isinstance(arg1, tuple) and isshape(arg1, allow_1d=is_array):

scipy/sparse/_lil.py

@@ -21,7 +21,7 @@ class _lil_base(_spbase, IndexMixin):
     _format = 'lil'
 
     def __init__(self, arg1, shape=None, dtype=None, copy=False):
-        _spbase.__init__(self)
+        _spbase.__init__(self, arg1)
         self.dtype = getdtype(dtype, arg1, default=float)
 
         # First get the shape

scipy/sparse/tests/test_construct.py

@@ -11,7 +11,11 @@
 
 from scipy.sparse import (csr_matrix, coo_matrix,
                           csr_array, coo_array,
-                          sparray, spmatrix,
+                          csc_array, bsr_array,
+                          dia_array, dok_array,
+                          lil_array, csc_matrix,
+                          bsr_matrix, dia_matrix,
+                          lil_matrix, sparray, spmatrix,
                           _construct as construct)
 from scipy.sparse._construct import rand as sprand
 
@@ -37,6 +41,35 @@ def _sprandn_array(m, n, density=0.01, format="coo", dtype=None, random_state=No
 
 
 class TestConstructUtils:
+
+    @pytest.mark.parametrize("cls", [
+        csc_array, csr_array, coo_array, bsr_array,
+        dia_array, dok_array, lil_array
+    ])
+    def test_singleton_array_constructor(self, cls):
+        with pytest.raises(
+            ValueError,
+            match=(
+                'scipy sparse array classes do not support '
+                'instantiation from a scalar'
+            )
+        ):
+            cls(0)
+
+    @pytest.mark.parametrize("cls", [
+        csc_matrix, csr_matrix, coo_matrix,
+        bsr_matrix, dia_matrix, lil_matrix
+    ])
+    def test_singleton_matrix_constructor(self, cls):
+        """
+        This test is for backwards compatibility post scipy 1.13.
+        The behavior observed here is what is to be expected
+        with the older matrix classes. This test comes with the
+        exception of dok_matrix, which was not working pre scipy1.12
+        (unlike the rest of these).
+        """
+        assert cls(0).shape == (1, 1)
+
     def test_spdiags(self):
         diags1 = array([[1, 2, 3, 4, 5]])
         diags2 = array([[1, 2, 3, 4, 5],