fix: allow colon in key names (#1127)

* fix: allow column in key names

* style: pre-commit fixes

* Rename test file to match PR number.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

src/uproot/reading.py

@@ -2060,6 +2060,8 @@ def __getitem__(self, where):
                                     keys=[key.fName for key in last._keys],
                                     file_path=self._file.file_path,
                                 )
+                        elif ":" in item and item in step:
+                            return self.key(where).get()
                         else:
                             last = step
                             step = step[item]

tests/test_1127_fix_allow_colon_in_key_names.py

@@ -0,0 +1,26 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/uproot5/blob/main/LICENSE
+
+import awkward as ak
+import uproot
+import skhep_testdata
+import numpy
+import os
+
+
+def test_colon_in_path_and_name(tmp_path):
+    newfile = os.path.join(tmp_path, "test_colon_in_name.root")
+    with uproot.recreate(newfile) as f:
+        f["one:two"] = "together"
+        array = ak.Array(["one", "two", "three"])
+        f["one"] = {"two": array}
+
+    with uproot.open(newfile) as f:
+        f["one:two"] == "together"
+        f["one"]["two"].array() == ["one", "two", "three"]
+
+
+def test_colon_reading_in_path():
+    with uproot.open(
+        skhep_testdata.data_path("uproot-small-evnt-tree-fullsplit.root")
+    ) as f:
+        f["tree:evt/P3/P3.Py"].array() == numpy.arange(100)