Fix tuples as on argument in merge (#1117)

dask_expr/_collection.py

@@ -5658,6 +5658,11 @@ def merge(
     if on and not left_on and not right_on:
         left_on = right_on = on
 
+    if pd.api.types.is_list_like(left_on) and not isinstance(left_on, FrameBase):
+        left_on = list(left_on)
+    if pd.api.types.is_list_like(right_on) and not isinstance(right_on, FrameBase):
+        right_on = list(right_on)
+
     supported_how = ("left", "right", "outer", "inner", "leftsemi")
     if how not in supported_how:
         raise ValueError(

dask_expr/tests/test_merge.py

@@ -1029,3 +1029,24 @@ def test_merge_after_rename(index):
     expected = pleft.merge(right, how="inner")
     result = left.merge(right, how="inner")
     assert_eq(result, expected, check_index=False)
+
+
+def test_merge_tuple_left_on():
+    df = pd.DataFrame(
+        {
+            "a": [1, 2, 3] * 5,
+            "b": [1, 2, 3] * 5,
+            "c": ["A"] * 15,
+        },
+    )
+    ddf = from_pandas(df, npartitions=2)
+    assert_eq(
+        ddf.merge(ddf, left_on=("a",), right_on=("a",)),
+        df.merge(df, left_on=("a",), right_on=("a",)),
+        check_index=False,
+    )
+    assert_eq(
+        ddf.merge(ddf, on=("a",)),
+        df.merge(df, on=("a",)),
+        check_index=False,
+    )

dask_expr/tests/test_resample.py

@@ -135,7 +135,7 @@ def test_resample_divisions_propagation():
     pdf = pd.DataFrame({"data": 1}, index=idx)
     df = from_pandas(pdf, npartitions=10)
     result = df.resample("0.03s").mean()
-    result = result.repartition(freq="1T")
+    result = result.repartition(freq="1d")
     expected = pdf.resample("0.03s").mean()
     assert_eq(result, expected)