StyledText subclasses: add copy() method

StyledText retrieved from style attributes needs to be copied because
we shouldn't reuse the same instance at different locations in the
document tree.

This fixes problems caused by Styled._style_name caching.

src/rinoh/flowable.py

@@ -489,7 +489,7 @@ def initial_state(self, container):
         flowables_iter = self.flowables(container)
         title_text = self.get_style('title', container)
         if title_text:
-            title = Paragraph(title_text, style='title')
+            title = Paragraph(title_text.copy(), style='title')
             flowables_iter = chain((title, ), flowables_iter)
         return GroupedFlowablesState(self, flowables_iter)
 

src/rinoh/number.py

@@ -11,6 +11,7 @@
 * :func:`format_number`: Format a number according to a given style.
 
 """
+from copy import copy
 
 from .attribute import Attribute, OptionSet, Bool
 from .paragraph import ParagraphBase, ParagraphStyle
@@ -100,7 +101,7 @@ def __init__(self, custom_label=None):
     def format_label(self, label, container):
         prefix = self.get_style('label_prefix', container) or ''
         suffix = self.get_style('label_suffix', container) or ''
-        return prefix + label + suffix
+        return copy(prefix) + copy(label) + copy(suffix)
 
 
 class NumberStyle(LabelStyle):

src/rinoh/reference.py

@@ -57,6 +57,10 @@ def __str__(self):
             result += ' ({})'.format(self.style)
         return result
 
+    def copy(self, parent=None):
+        return type(self)(self.type, self.link, self.quiet,
+                          style=self.style, parent=parent)
+
     def target_id(self, document):
         raise NotImplementedError
 
@@ -167,7 +171,7 @@ def __init__(self, target_id_or_flowable, id=None, style=None, parent=None):
         self.target_id_or_flowable = target_id_or_flowable
 
     def text(self, container):
-        return MixedStyledText(self.get_style('text', container), parent=self)
+        return self.get_style('text', container).copy(parent=self)
 
     def _target_id(self, document):
         target_id_or_flowable = self.target_id_or_flowable

src/rinoh/style.py

@@ -459,8 +459,7 @@ def nesting_level(self):
             return 0
 
     def configuration_name(self, document):
-        try:
-            # raise AttributeError
+        try:    # TODO: make document hashable so @cached can be used?
             return self._style_name
         except AttributeError:
             ruleset = self.configuration_class.get_ruleset(document)

src/rinoh/text.py

@@ -79,14 +79,12 @@ def wrapped_spans(self, container):
         """Generator yielding all spans in this inline element (flattened)"""
         before = self.get_style('before', container)
         if before is not None:
-            before.parent = self.parent
-            yield from before.wrapped_spans(container)
+            yield from before.copy(self.parent).wrapped_spans(container)
         if not self.get_style('hide', container):
             yield from self.spans(container)
         after = self.get_style('after', container)
         if after is not None:
-            after.parent = self.parent
-            yield from after.wrapped_spans(container)
+            yield from after.copy(self.parent).wrapped_spans(container)
 
     def spans(self, container):
         raise NotImplementedError
@@ -129,7 +127,10 @@ def __iadd__(self, other):
         is `None`, this styled text itself is returned."""
         return self + other
 
-    def copy(self, id=None, style=None, parent=None):
+    def __copy__(self):
+        return self.copy()
+
+    def copy(self, parent=None):
         raise NotImplementedError
 
     @classmethod
@@ -381,6 +382,9 @@ def __str__(self):
     def text(self, container, **kwargs):
         return self._text
 
+    def copy(self, parent=None):
+        return type(self)(self._text, style=self.style, parent=parent)
+
 
 class MixedStyledTextBase(StyledText):
     def to_string(self, flowable_target):
@@ -477,6 +481,10 @@ def items(self):
     def children(self, flowable_target):
         return self.items
 
+    def copy(self, parent=None):
+        items = [item.copy() for item in self.items]
+        return type(self)(items, style=self.style, parent=parent)
+
 
 class ConditionalMixedStyledText(MixedStyledText):
     def __init__(self, text_or_items, document_option, style=None, parent=None):
@@ -578,14 +586,17 @@ class ControlCharacter(Character, metaclass=ControlCharacterMeta):
     exception = Exception
     all = {}
 
-    def __init__(self):
+    def __init__(self, style=None, parent=None):
         """Initialize this control character with it's unicode `char`."""
-        super().__init__(self.character)
+        super().__init__(self.character, style=style, parent=parent)
 
     def __repr__(self):
         """A textual representation of this control character."""
         return self.__class__.__name__
 
+    def copy(self, parent=None):
+        return type(self)(style=self.style, parent=parent)
+
     @property
     def width(self):
         """Raises the exception associated with this control character.