From 2d015dd17ff2c775ad8f23d19c5a67da514314b2 Mon Sep 17 00:00:00 2001
From: Jean-Luc Stevens <jlrstevens@gmail.com>
Date: Tue, 15 Jan 2019 20:13:28 -0600
Subject: [PATCH] Fixed handling of characters that have no uppercase (#3403)

---
 holoviews/core/tree.py              |  8 +++++---
 holoviews/core/util.py              | 13 +++++++++++++
 holoviews/tests/core/testlayouts.py | 17 +++++++++++++++--
 holoviews/tests/core/testutils.py   | 18 +++++++++++++++++-
 4 files changed, 50 insertions(+), 6 deletions(-)

diff --git a/holoviews/core/tree.py b/holoviews/core/tree.py
index 27568567c3..5464e74c0e 100644
--- a/holoviews/core/tree.py
+++ b/holoviews/core/tree.py
@@ -218,12 +218,13 @@ def __delitem__(self, identifier):
     def __setattr__(self, identifier, val):
         # Getattr is skipped for root and first set of children
         shallow = (self.parent is None or self.parent.parent is None)
-        if identifier[0].isupper() and self.fixed and shallow:
+
+        if util.tree_attribute(identifier) and self.fixed and shallow:
             raise AttributeError(self._fixed_error % identifier)
 
         super(AttrTree, self).__setattr__(identifier, val)
 
-        if identifier[0].isupper():
+        if util.tree_attribute(identifier):
             if not identifier in self.children:
                 self.children.append(identifier)
             self._propagate((identifier,), val)
@@ -254,7 +255,8 @@ def __getattr__(self, identifier):
         if sanitized in self.children:
             return self.__dict__[sanitized]
 
-        if not sanitized.startswith('_') and identifier[0].isupper():
+
+        if not sanitized.startswith('_') and util.tree_attribute(identifier):
             self.children.append(sanitized)
             dir_mode = self.__dict__['_dir_mode']
             child_tree = self.__class__(identifier=sanitized,
diff --git a/holoviews/core/util.py b/holoviews/core/util.py
index c61eb5b7a4..cba7e7fd63 100644
--- a/holoviews/core/util.py
+++ b/holoviews/core/util.py
@@ -338,6 +338,19 @@ def deephash(obj):
         return None
 
 
+def tree_attribute(identifier):
+    """
+    Predicate that returns True for custom attributes added to AttrTrees
+    that are not methods, properties or internal attributes.
+
+    These custom attributes start with a capitalized character when
+    applicable (not applicable to underscore or certain unicode characters)
+    """
+    if identifier[0].upper().isupper() is False and identifier[0] != '_':
+        return True
+    else:
+        return identifier[0].isupper()
+
 def argspec(callable_obj):
     """
     Returns an ArgSpec object for functions, staticmethods, instance
diff --git a/holoviews/tests/core/testlayouts.py b/holoviews/tests/core/testlayouts.py
index ac57222715..3a26071035 100644
--- a/holoviews/tests/core/testlayouts.py
+++ b/holoviews/tests/core/testlayouts.py
@@ -1,7 +1,13 @@
+# -*- coding: utf-8 -*-
+"""
+Tests of Layout and related classes
+"""
+
+import sys
 from holoviews import AdjointLayout, NdLayout, GridSpace, Layout, Element, HoloMap, Overlay
-from holoviews.element import HLine
+from holoviews.element import HLine, Curve
 from holoviews.element.comparison import ComparisonTestCase
-
+from unittest import SkipTest
 
 class CompositeTest(ComparisonTestCase):
     "For testing of basic composite element types"
@@ -19,6 +25,13 @@ def setUp(self):
     def test_add_operator(self):
         self.assertEqual(type(self.view1 + self.view2), Layout)
 
+    def test_add_unicode_py3(self):
+        "Test to avoid regression of #3403 where unicode characters don't capitalize"
+        if sys.version_info.major == 2: raise SkipTest
+        layout = Curve([-1,-2,-3]) + Curve([1,2,3]) .relabel('𝜗_1 vs th_2')
+        elements = list(layout)
+        self.assertEqual(len(elements), 2)
+
 
 class AdjointLayoutTest(CompositeTest):
 
diff --git a/holoviews/tests/core/testutils.py b/holoviews/tests/core/testutils.py
index 097a1dceb3..b1e2b37995 100644
--- a/holoviews/tests/core/testutils.py
+++ b/holoviews/tests/core/testutils.py
@@ -19,7 +19,7 @@
     sanitize_identifier_fn, find_range, max_range, wrap_tuple_streams,
     deephash, merge_dimensions, get_path, make_path_unique, compute_density,
     date_range, dt_to_int, compute_edges, isfinite, cross_index, closest_match,
-    dimension_range
+    dimension_range, tree_attribute
 )
 from holoviews import Dimension, Element
 from holoviews.streams import PointerXY
@@ -191,6 +191,22 @@ def test_prefix_test3_py3(self):
         self.assertEqual(prefixed, True)
 
 
+class TestTreeAttribute(ComparisonTestCase):
+
+    def test_simple_lowercase_string(self):
+        self.assertEqual(tree_attribute('lowercase'), False)
+
+    def test_simple_uppercase_string(self):
+        self.assertEqual(tree_attribute('UPPERCASE'), True)
+
+    def test_unicode_string(self):
+        if py_version != 2: raise SkipTest
+        self.assertEqual(tree_attribute('𝜗unicode'), True)
+
+    def test_underscore_string(self):
+        self.assertEqual(tree_attribute('_underscore'), False)
+
+
 class TestSanitizationPy2(ComparisonTestCase):
     """
     Tests of sanitize_identifier (Python 2)