fix: Fix internal type errors with temporal accessors (#2125)

TrevorBergeron · web-flow · commit c390da11b7c2 · 2025-10-02T10:40:31.000-07:00
diff --git a/bigframes/operations/datetimes.py b/bigframes/operations/datetimes.py
@@ -23,7 +23,6 @@
 
 from bigframes import dataframe, dtypes, series
 from bigframes.core import log_adapter
-from bigframes.core.reshape import concat
 import bigframes.operations as ops
 import bigframes.operations.base
 
@@ -79,13 +78,12 @@ def month(self) -> series.Series:
         return self._apply_unary_op(ops.month_op)
 
     def isocalendar(self) -> dataframe.DataFrame:
-        years = self._apply_unary_op(ops.iso_year_op)
-        weeks = self._apply_unary_op(ops.iso_week_op)
-        days = self._apply_unary_op(ops.iso_day_op)
-
-        result = concat.concat([years, weeks, days], axis=1)
-        result.columns = pandas.Index(["year", "week", "day"])
-        return result
+        iso_ops = [ops.iso_year_op, ops.iso_week_op, ops.iso_day_op]
+        labels = pandas.Index(["year", "week", "day"])
+        block = self._block.project_exprs(
+            [op.as_expr(self._value_column) for op in iso_ops], labels, drop=True
+        )
+        return dataframe.DataFrame(block)
 
     # Time accessors
     @property
diff --git a/tests/system/small/operations/test_dates.py b/tests/system/small/operations/test_dates.py
@@ -15,8 +15,10 @@
 
 import datetime
 
+from packaging import version
 import pandas as pd
 import pandas.testing
+import pytest
 
 from bigframes import dtypes
 
@@ -71,3 +73,19 @@ def test_date_series_diff_agg(scalars_dfs):
     pandas.testing.assert_series_equal(
         actual_result, expected_result, check_index_type=False
     )
+
+
+def test_date_can_cast_after_accessor(scalars_dfs):
+    if version.Version(pd.__version__) <= version.Version("2.1.0"):
+        pytest.skip("pd timezone conversion bug")
+    bf_df, pd_df = scalars_dfs
+
+    actual_result = bf_df["date_col"].dt.isocalendar().week.astype("Int64").to_pandas()
+    # convert to pd date type rather than arrow, as pandas doesn't handle arrow date well here
+    expected_result = (
+        pd.to_datetime(pd_df["date_col"]).dt.isocalendar().week.astype("Int64")
+    )
+
+    pandas.testing.assert_series_equal(
+        actual_result, expected_result, check_dtype=False, check_index_type=False
+    )
diff --git a/third_party/bigframes_vendored/ibis/expr/operations/strings.py b/third_party/bigframes_vendored/ibis/expr/operations/strings.py
@@ -364,14 +364,14 @@ class ExtractFragment(ExtractURLField):
 class StringLength(StringUnary):
     """Compute the length of a string."""
 
-    dtype = dt.int32
+    dtype = dt.int64
 
 
 @public
 class StringAscii(StringUnary):
     """Compute the ASCII code of the first character of a string."""
 
-    dtype = dt.int32
+    dtype = dt.int64
 
 
 @public
diff --git a/third_party/bigframes_vendored/ibis/expr/operations/temporal.py b/third_party/bigframes_vendored/ibis/expr/operations/temporal.py
@@ -105,7 +105,7 @@ class ExtractTemporalField(Unary):
     """Extract a field from a temporal value."""
 
     arg: Value[dt.Temporal]
-    dtype = dt.int32
+    dtype = dt.int64
 
 
 @public
