Also state when a property doesn't support subscripting

Shows the property that doesn't support it.
Need to still update the tests though.

Author: nicholas-esterer

packages/python/plotly/_plotly_utils/utils.py

@@ -318,10 +318,11 @@ def split_string_positions(ss):
     )
 
 
-def display_string_positions(p, i=None):
+def display_string_positions(p, i=None, offset=0, length=1, char="^", trim=True):
     """
-    Return a string that is whitespace except at p[i] which is replaced with ^.
-    If i is None then all the indices of the string in p are replaced with ^.
+    Return a string that is whitespace except at p[i] which is replaced with char.
+    If i is None then all the indices of the string in p are replaced with char.
+
     Example:
 
         >>> ss = ["a.string[0].with_separators"]
@@ -334,13 +335,30 @@ def display_string_positions(p, i=None):
         'a.string[0].with_separators'
         >>> display_string_positions(ss_pos,4)
         '            ^'
+        >>> display_string_positions(ss_pos,4,offset=1,length=3,char="~",trim=False)
+        '             ~~~      '
+        >>> display_string_positions(ss_pos_)
+        '^ ^      ^ ^^    ^'
     :param (list) p: A list of integers.
     :param (integer|None) i: Optional index of p to display.
+    :param (integer) offset: Allows adding a number of spaces to the replacement.
+    :param (integer) length: Allows adding a replacement that is the char
+                             repeated length times.
+    :param (str) char: allows customizing the replacement character.
+    :param (boolean) trim: trims the remaining whitespace if True.
     """
-    s = [" " for _ in range(max(p) + 1)]
+    s = [" " for _ in range(max(p) + 1 + offset + length)]
+    maxaddr = 0
     if i is None:
         for p_ in p:
-            s[p_] = "^"
+            for l in range(length):
+                maxaddr = p_ + offset + l
+                s[maxaddr] = char
     else:
-        s[p[i]] = "^"
-    return "".join(s)
+        for l in range(length):
+            maxaddr = p[i] + offset + l
+            s[maxaddr] = char
+    ret = "".join(s)
+    if trim:
+        ret = ret[: maxaddr + 1]
+    return ret

packages/python/plotly/plotly/basedatatypes.py

@@ -119,20 +119,37 @@ def _check_path_in_prop_tree(obj, path):
         path = _remake_path_from_tuple(path)
     prop, prop_idcs = _str_to_dict_path_full(path)
     for i, p in enumerate(prop):
+        arg = ""
         try:
             obj = obj[p]
-        except (ValueError, KeyError, IndexError) as e:
-            arg = (
-                e.args[0]
-                + """
+        except (ValueError, KeyError, IndexError, TypeError) as e:
+            arg = e.args[0]
+            if obj is None:
+                # If obj doesn't support subscripting, state that and show the
+                # (valid) property that gives the object that doesn't support
+                # it.
+                # In case i is 0, the best we can do is indicate the first
+                # property in the string as having caused the error
+                disp_i = max(i - 1, 0)
+                arg += """
+Property does not support subscripting:
+%s
+%s""" % (
+                    path,
+                    display_string_positions(
+                        prop_idcs, disp_i, length=len(prop[disp_i]), char="~"
+                    ),
+                )
+            else:
+                # State that the property for which subscripting was attempted
+                # is bad and indicate the start of the bad property.
+                arg += """
 Bad property path:
-%s"""
-                % (path,)
-            )
-            arg += """
+%s
 %s""" % (
-                display_string_positions(prop_idcs, i),
-            )
+                    path,
+                    display_string_positions(prop_idcs, i, length=1, char="^"),
+                )
             # Make KeyError more pretty by changing it to a PlotlyKeyError,
             # because the Python interpreter has a special way of printing
             # KeyError