refactor: propagate attrs & behavior with dict-like ak.Array input …

…data (#3374)

* refactor: propagate attrs & behavior from given input arrays in the same way as ak.zip

* add test

src/awkward/highlevel.py

@@ -302,19 +302,22 @@ def __init__(
 
         elif isinstance(data, dict):
             fields = []
-            contents = []
+            _arrays = []
             length = None
             for k, v in data.items():
                 fields.append(k)
-                contents.append(Array(v).layout)
+                _arrays.append(Array(v))
                 if length is None:
-                    length = contents[-1].length
-                elif length != contents[-1].length:
+                    length = _arrays[-1].layout.length
+                elif length != _arrays[-1].layout.length:
                     raise ValueError(
                         "dict of arrays in ak.Array constructor must have arrays "
-                        f"of equal length ({length} vs {contents[-1].length})"
+                        f"of equal length ({length} vs {_arrays[-1].layout.length}). "
+                        "For automatic broadcasting use 'ak.zip' instead. "
                     )
-            layout = ak.contents.RecordArray(contents, fields)
+            layout = ak.contents.RecordArray([arr.layout for arr in _arrays], fields)
+            attrs = attrs_of(*_arrays, attrs=attrs)
+            behavior = behavior_of(*_arrays, behavior=behavior)
 
         elif isinstance(data, str):
             layout = ak.operations.from_json(data, highlevel=False)

tests/test_3374_propagate_metadata_akArray_dictlike_data.py

@@ -0,0 +1,32 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/awkward/blob/main/LICENSE
+# ruff: noqa: E402
+
+from __future__ import annotations
+
+import awkward as ak
+
+
+def test_attrs():
+    x = ak.Array([1], attrs={"me": "ta"})
+    y = ak.Array([1], attrs={"da": "ta"})
+
+    rec = ak.Array({"x": x, "y": y})
+    assert rec.attrs == {"me": "ta", "da": "ta"}
+
+    # overwrite attrs:
+    rec = ak.Array({"x": x, "y": y}, attrs={"foo": "bar"})
+    assert rec.attrs == {"foo": "bar"}
+
+
+def test_behaviors():
+    behavior = {"foo": object()}
+    x = ak.Array([1], behavior=behavior)
+    y = ak.Array([1], behavior=behavior)
+
+    rec = ak.Array({"x": x, "y": y})
+    assert rec.behavior == behavior
+
+    # overwrite behavior:
+    behavior2 = {"bar": object()}
+    rec = ak.Array({"x": x, "y": y}, behavior=behavior2)
+    assert rec.behavior == behavior2