Enable chaining of lazy expressions for logical operators

Author: Luke Shaw

src/blosc2/lazyexpr.py

@@ -1919,7 +1919,6 @@ def update_expr(self, new_op):  # noqa: C901
         if hasattr(value2, "_where_args"):
             value2 = value2.compute()
 
-        self._dtype = infer_dtype(op, value1, value2)
         if not isinstance(value1, LazyExpr) and not isinstance(value2, LazyExpr):
             # We converted some of the operands to NDArray (where() handling above)
             new_operands = {"o0": value1, "o1": value2}
@@ -2677,8 +2676,8 @@ def _new_expr(cls, expression, operands, guess, out=None, where=None, ne_args=No
             _shape = new_expr.shape
             if isinstance(new_expr, blosc2.LazyExpr):
                 # Restore the original expression and operands
-                new_expr.expression = _expression
-                new_expr.expression_tosave = expression
+                new_expr.expression = f"({_expression})"  # forcibly add parenthesis
+                new_expr.expression_tosave = new_expr.expression
                 new_expr.operands = _operands
                 new_expr.operands_tosave = operands
             else:

tests/ndarray/test_lazyexpr.py

@@ -1220,6 +1220,10 @@ def test_dtype_infer(dtype1, dtype2, scalar):
     np.testing.assert_allclose(res, nres)
     assert res.dtype == nres.dtype
 
+    # Check dtype not changed by expression creation (bug fix)
+    assert a.dtype == dtype1
+    assert b.dtype == dtype2
+
 
 @pytest.mark.parametrize(
     "cfunc", ["np.int8", "np.int16", "np.int32", "np.int64", "np.float32", "np.float64"]
@@ -1330,3 +1334,21 @@ def test_missing_operator():
     # Clean up
     blosc2.remove_urlpath("a.b2nd")
     blosc2.remove_urlpath("expr.b2nd")
+
+
+# Test the chaining of multiple lazy expressions
+def test_chain_expressions():
+    N = 1_000
+    dtype = "float64"
+    a = blosc2.linspace(0, 1, N * N, dtype=dtype, shape=(N, N))
+    b = blosc2.linspace(1, 2, N * N, dtype=dtype, shape=(N, N))
+    c = blosc2.linspace(0, 1, N, dtype=dtype, shape=(N,))
+
+    le1 = a**3 + blosc2.sin(a**2)
+    le2 = le1 < c
+    le3 = le2 & (b < 0)
+
+    le1_ = blosc2.lazyexpr("a ** 3 + sin(a ** 2)", {"a": a})
+    le2_ = blosc2.lazyexpr("(le1 < c)", {"le1": le1_, "c": c})
+    le3_ = blosc2.lazyexpr("(le2 & (b < 0))", {"le2": le2_, "b": b})
+    assert (le3_[:] == le3[:]).all()