feat: make map(), struct(), array() idempotent

Before `array(array([1,2]))` would error.
Now it doesn't

This is in prep for the next commit.
But it also is just a nice behavior, where
you can now call these functions as many times as you want and always get back something that makes sense.

Also, fix a typing bug: map() can accept ArrayValues, not just ArrayColumns

ibis/expr/types/arrays.py

@@ -6,13 +6,13 @@
 from public import public
 
 import ibis.expr.operations as ops
+import ibis.expr.types as ir
 from ibis.common.deferred import Deferred, deferrable
 from ibis.expr.types.generic import Column, Scalar, Value
 
 if TYPE_CHECKING:
     from collections.abc import Iterable
 
-    import ibis.expr.types as ir
     from ibis.expr.types.typing import V
 
 import ibis.common.exceptions as com
@@ -1081,7 +1081,7 @@ def __getitem__(self, index: int | ir.IntegerValue | slice) -> ir.Column:
 
 @public
 @deferrable
-def array(values: Iterable[V]) -> ArrayValue:
+def array(values: ArrayValue | Iterable[V]) -> ArrayValue:
     """Create an array expression.
 
     If any values are [column expressions](../concepts/datatypes.qmd) the
@@ -1131,4 +1131,6 @@ def array(values: Iterable[V]) -> ArrayValue:
     │ [3, 47]              │
     └──────────────────────┘
     """
+    if isinstance(values, ir.ArrayValue):
+        return values
     return ops.Array(tuple(values)).to_expr()

ibis/expr/types/maps.py

@@ -5,15 +5,13 @@
 from public import public
 
 import ibis.expr.operations as ops
+import ibis.expr.types as ir
 from ibis.common.deferred import deferrable
 from ibis.expr.types.generic import Column, Scalar, Value
 
 if TYPE_CHECKING:
     from collections.abc import Iterable, Mapping
 
-    import ibis.expr.types as ir
-    from ibis.expr.types.arrays import ArrayColumn
-
 
 @public
 class MapValue(Value):
@@ -435,8 +433,8 @@ def __getitem__(self, key: ir.Value) -> ir.Column:
 @public
 @deferrable
 def map(
-    keys: Iterable[Any] | Mapping[Any, Any] | ArrayColumn,
-    values: Iterable[Any] | ArrayColumn | None = None,
+    keys: Iterable[Any] | Mapping[Any, Any] | ir.ArrayValue | MapValue,
+    values: Iterable[Any] | ir.ArrayValue | None = None,
 ) -> MapValue:
     """Create a MapValue.
 
@@ -486,6 +484,8 @@ def map(
     │ {'b': 3}             │
     └──────────────────────┘
     """
+    if isinstance(keys, MapValue):
+        return keys
     if values is None:
         keys, values = tuple(keys.keys()), tuple(keys.values())
     return ops.Map(keys, values).to_expr()

ibis/expr/types/structs.py

@@ -22,7 +22,7 @@
 @public
 @deferrable
 def struct(
-    value: Iterable[tuple[str, V]] | Mapping[str, V],
+    value: Iterable[tuple[str, V]] | Mapping[str, V] | StructValue,
     type: str | dt.DataType | None = None,
 ) -> StructValue:
     """Create a struct expression.
@@ -75,6 +75,11 @@ def struct(
     """
     import ibis.expr.operations as ops
 
+    if isinstance(value, StructValue):
+        if type is not None:
+            return value.cast(type)
+        return value
+
     fields = dict(value)
     if any(isinstance(value, Value) for value in fields.values()):
         names = tuple(fields.keys())