TST: Add test for missing conversion

Add test to ensure conversion of large ints is correct

Author: bashtage

pandas/io/stata.py

@@ -469,7 +469,7 @@ class PossiblePrecisionLoss(Warning):
 
 
 precision_loss_doc = """
-Column converted from %s to %s, and some data are outside of the lossless
+Column converted from {0} to {1}, and some data are outside of the lossless
 conversion range. This may result in a loss of precision in the saved data.
 """
 

pandas/tests/io/test_stata.py

@@ -1980,3 +1980,20 @@ def test_iterator_value_labels():
             for i in range(2):
                 tm.assert_index_equal(chunk.dtypes[i].categories, expected)
             tm.assert_frame_equal(chunk, df.iloc[j * 100 : (j + 1) * 100])
+
+
+def test_precision_loss():
+    df = pd.DataFrame(
+        [[sum(2 ** i for i in range(60)), sum(2 ** i for i in range(52))]],
+        columns=["big", "little"],
+    )
+    with tm.ensure_clean() as path:
+        with tm.assert_produces_warning(
+            PossiblePrecisionLoss, match="Column converted from int64 to float64"
+        ):
+            df.to_stata(path, write_index=False)
+        reread = pd.read_stata(path)
+        expected_dt = pd.Series([np.float64, np.float64], index=["big", "little"])
+        tm.assert_series_equal(reread.dtypes, expected_dt)
+        assert reread.loc[0, "little"] == df.loc[0, "little"]
+        assert reread.loc[0, "big"] == float(df.loc[0, "big"])