fix: dask failing for TTrees with duplicate TBranch names (#1189)

* fix: dask failing for TTrees with duplicate TBranch names

* style: pre-commit fixes

* Update _dask.py

* Test file name update

* preserve order in `common_keys` while dropping duplicates

---------

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

src/uproot/_dask.py

@@ -606,6 +606,7 @@ def real_filter_branch(branch):
                 filter_typename=filter_typename,
                 filter_branch=real_filter_branch,
                 full_paths=full_paths,
+                ignore_duplicates=True,
             )
 
             if common_keys is None:
@@ -747,6 +748,7 @@ def _get_dask_array_delay_open(
         filter_typename=filter_typename,
         filter_branch=filter_branch,
         full_paths=full_paths,
+        ignore_duplicates=True,
     )
 
     dask_dict = {}
@@ -1441,6 +1443,7 @@ def real_filter_branch(branch):
                 filter_typename=filter_typename,
                 filter_branch=real_filter_branch,
                 full_paths=full_paths,
+                ignore_duplicates=True,
             )
 
             if common_keys is None:
@@ -1586,7 +1589,7 @@ def _get_dak_array_delay_open(
     ffile_path, fobject_path = files[0][0:2]
 
     if known_base_form is not None:
-        common_keys = list(known_base_form.fields)
+        common_keys = list(dict.fromkeys(known_base_form.fields))
         base_form = known_base_form
     else:
         obj = uproot._util.regularize_object_path(
@@ -1598,6 +1601,7 @@ def _get_dak_array_delay_open(
             filter_typename=filter_typename,
             filter_branch=filter_branch,
             full_paths=full_paths,
+            ignore_duplicates=True,
         )
         base_form = _get_ttree_form(
             awkward, obj, common_keys, interp_options.get("ak_add_doc")

src/uproot/behaviors/TBranch.py

@@ -1126,6 +1126,7 @@ def keys(
         filter_branch=no_filter,
         recursive=True,
         full_paths=True,
+        ignore_duplicates=False,
     ):
         """
         Args:
@@ -1143,6 +1144,7 @@ def keys(
             full_paths (bool): If True, include the full path to each subbranch
                 with slashes (``/``); otherwise, use the descendant's name as
                 the output name.
+            ignore_duplicates (bool): If True, return a set of the keys; otherwise, return the full list of keys.
 
         Returns the names of the subbranches as a list of strings.
         """
@@ -1153,6 +1155,7 @@ def keys(
                 filter_branch=filter_branch,
                 recursive=recursive,
                 full_paths=full_paths,
+                ignore_duplicates=ignore_duplicates,
             )
         )
 
@@ -1279,6 +1282,7 @@ def iterkeys(
         filter_branch=no_filter,
         recursive=True,
         full_paths=True,
+        ignore_duplicates=False,
     ):
         """
         Args:
@@ -1296,6 +1300,8 @@ def iterkeys(
             full_paths (bool): If True, include the full path to each subbranch
                 with slashes (``/``); otherwise, use the descendant's name as
                 the output name.
+            ignore_duplicates (bool): If True, return a set of the keys; otherwise, return the full list of keys.
+
 
         Returns the names of the subbranches as an iterator over strings.
         """
@@ -1305,6 +1311,7 @@ def iterkeys(
             filter_branch=filter_branch,
             recursive=recursive,
             full_paths=full_paths,
+            ignore_duplicates=ignore_duplicates,
         ):
             yield k
 
@@ -1353,6 +1360,7 @@ def iteritems(
         filter_branch=no_filter,
         recursive=True,
         full_paths=True,
+        ignore_duplicates=False,
     ):
         """
         Args:
@@ -1370,6 +1378,8 @@ def iteritems(
             full_paths (bool): If True, include the full path to each subbranch
                 with slashes (``/``) in the name; otherwise, use the descendant's
                 name as the name without modification.
+            ignore_duplicates (bool): If True, return a set of the keys; otherwise, return the full list of keys.
+
 
         Returns (name, branch) pairs of the subbranches as an iterator over
         2-tuples of (str, :doc:`uproot.behaviors.TBranch.TBranch`).
@@ -1385,6 +1395,8 @@ def iteritems(
                 f"filter_branch must be None or a function: TBranch -> bool, not {filter_branch!r}"
             )
 
+        keys_set = set()
+
         for branch in self.branches:
             if (
                 (
@@ -1394,7 +1406,11 @@ def iteritems(
                 and (filter_typename is no_filter or filter_typename(branch.typename))
                 and (filter_branch is no_filter or filter_branch(branch))
             ):
-                yield branch.name, branch
+                if ignore_duplicates and branch.name in keys_set:
+                    pass
+                else:
+                    keys_set.add(branch.name)
+                    yield branch.name, branch
 
             if recursive:
                 for k1, v in branch.iteritems(
@@ -1408,7 +1424,11 @@ def iteritems(
                     if filter_name is no_filter or _filter_name_deep(
                         filter_name, self, v
                     ):
-                        yield k2, v
+                        if ignore_duplicates and branch.name in keys_set:
+                            pass
+                        else:
+                            keys_set.add(k2)
+                            yield k2, v
 
     def itertypenames(
         self,

tests/test_1189_dask_failing_on_duplicate_keys.py

@@ -0,0 +1,21 @@
+# BSD 3-Clause License; see https://github.com/scikit-hep/uproot5/blob/main/LICENSE
+
+import pytest
+import uproot
+import skhep_testdata
+
+
+def test_dask_duplicated_keys():
+
+    lazy = uproot.dask(
+        skhep_testdata.data_path("uproot-metadata-performance.root") + ":Events"
+    )
+    materialized = lazy.FatJet_btagDDBvLV2.compute()
+
+    lazy = uproot.dask(skhep_testdata.data_path("uproot-issue513.root") + ":Delphes")
+    materialized = lazy.Particle.compute()
+
+    lazy = uproot.dask(
+        skhep_testdata.data_path("uproot-issue443.root") + ":muonDataTree"
+    )
+    materialized = lazy.hitEnd.compute()