fix(python): Handle boolean comparisons in Iceberg predicate pushdown

Filtering columns on boolean literals failed trying to parse
`pa.compute.scalar(True)`. This updates the Call predicate parser to
handle the `scalar` type.

py-polars/polars/io/iceberg.py

@@ -245,6 +245,8 @@ def _(a: Call) -> Any:
     f = _convert_predicate(a.func)
     if f == "field":
         return args
+    elif f == "scalar":
+        return args[0]
     elif f in _temporal_conversions:
         # convert from polars-native i64 to ISO8601 string
         return _temporal_conversions[f](*args).isoformat()

py-polars/tests/unit/io/test_iceberg.py

@@ -163,3 +163,12 @@ def test_parse_lteq(self) -> None:
 
         expr = _to_ast("(pa.compute.field('ts') <= '2023-08-08')")
         assert _convert_predicate(expr) == LessThanOrEqual("ts", "2023-08-08")
+
+    def test_compare_boolean(self) -> None:
+        from pyiceberg.expressions import EqualTo
+
+        expr = _to_ast("(pa.compute.field('ts') == pa.compute.scalar(True))")
+        assert _convert_predicate(expr) == EqualTo("ts", True)
+
+        expr = _to_ast("(pa.compute.field('ts') == pa.compute.scalar(False))")
+        assert _convert_predicate(expr) == EqualTo("ts", False)