reimplement CommentedSeq to subclass MutableSequence instead of list

re issue #176

4 files changed, 67 insertions, 48 deletions

diff --git a/_test/test_issues.py b/_test/test_issues.py
index 7c779d7..9539dc5 100644
--- a/_test/test_issues.py
+++ b/_test/test_issues.py
@@ -39,8 +39,8 @@ class TestIssues:
         from ruamel import yaml
 
         import re
-        
-        
+
+
         class SINumber(yaml.YAMLObject):
             PREFIXES = {'k': 1e3, 'M': 1e6, 'G': 1e9}
             yaml_loader = yaml.Loader
@@ -48,29 +48,29 @@ class TestIssues:
             yaml_tag = u'!si'
             yaml_implicit_pattern = re.compile(
                 r'^(?P<value>[0-9]+(?:\.[0-9]+)?)(?P<prefix>[kMG])$')
-        
+
             @classmethod
             def from_yaml(cls, loader, node):
                 return cls(node.value)
-        
+
             @classmethod
             def to_yaml(cls, dumper, data):
                 return dumper.represent_scalar(cls.yaml_tag, str(data))
-        
+
             def __init__(self, *args):
                 m = self.yaml_implicit_pattern.match(args[0])
                 self.value = float(m.groupdict()['value'])
                 self.prefix = m.groupdict()['prefix']
-        
+
             def __str__(self):
                 return str(self.value)+self.prefix
-        
+
             def __int__(self):
                 return int(self.value*self.PREFIXES[self.prefix])
-        
+
         # This fails:
         yaml.add_implicit_resolver(SINumber.yaml_tag, SINumber.yaml_implicit_pattern)
-        
+
         ret = yaml.load("""
         [1,2,3, !si 10k, 100G]
         """, Loader=yaml.Loader)
@@ -83,7 +83,6 @@ class TestIssues:
         yaml_str = "[1, 2, 3, !si 10k, 100G]\n"
         x = round_trip(yaml_str, preserve_quotes=True)  # NOQA
 
-
     def test_issue_102(self):
         yaml_str = dedent("""
         var1: #empty
diff --git a/comments.py b/comments.py
index c98baf8..2063775 100644
--- a/comments.py
+++ b/comments.py
@@ -12,7 +12,7 @@ import sys
 import copy
 
 
-from ruamel.yaml.compat import ordereddict, PY2, string_types
+from ruamel.yaml.compat import ordereddict, PY2, string_types, MutableSequence
 from ruamel.yaml.scalarstring import ScalarString
 
 if PY2:
@@ -385,42 +385,73 @@ class CommentedBase(object):
         raise NotImplementedError
 
 
-class CommentedSeq(list, CommentedBase):
-    __slots__ = (Comment.attrib,)
+class CommentedSeq(MutableSequence, CommentedBase):
+    __slots__ = (Comment.attrib, '_lst')
 
-    def _yaml_add_comment(self, comment, key=NoComment):
-        # type: (Any, Optional[Any]) -> None
-        if key is not NoComment:
-            self.yaml_key_comment_extend(key, comment)
-        else:
-            self.ca.comment = comment
+    def __init__(self, *args, **kw):
+        # type: (Any, Any) -> None
+        self._lst = list(*args, **kw)
 
-    def _yaml_add_eol_comment(self, comment, key):
+    def __getitem__(self, idx):
+        # type: (Any) -> Any
+        return self._lst[idx]
+
+    def __setitem__(self, idx, value):
         # type: (Any, Any) -> None
-        self._yaml_add_comment(comment, key=key)
+        # try to preserve the scalarstring type if setting an existing key to a new value
+        if idx < len(self):
+            if (
+                isinstance(value, string_types)
+                and not isinstance(value, ScalarString)
+                and isinstance(self[idx], ScalarString)
+            ):
+                value = type(self[idx])(value)
+        self._lst.__setitem__(idx, value)
 
-    def _yaml_get_columnX(self, key):
+    def __delitem__(self, idx=None):
         # type: (Any) -> Any
-        return self.ca.items[key][0].start_mark.column
+        del self._lst[idx]
+        self.ca.items.pop(idx, None)  # might not be there -> default value
+        for list_index in sorted(self.ca.items):
+            if list_index < idx:
+                continue
+            self.ca.items[list_index - 1] = self.ca.items.pop(list_index)
+
+    def __len__(self):
+        # type: () -> int
+        return len(self._lst)
 
     def insert(self, idx, val):
         # type: (Any, Any) -> None
         """the comments after the insertion have to move forward"""
-        list.insert(self, idx, val)
+        self._lst.insert(idx, val)
         for list_index in sorted(self.ca.items, reverse=True):
             if list_index < idx:
                 break
             self.ca.items[list_index + 1] = self.ca.items.pop(list_index)
 
-    def pop(self, idx=None):
+    def extend(self, val):
+        # type: (Any) -> None
+        self._lst.extend(val)
+
+    def __eq__(self, other):
+        # type: (Any) -> bool
+        return bool(self._lst == other)
+
+    def _yaml_add_comment(self, comment, key=NoComment):
+        # type: (Any, Optional[Any]) -> None
+        if key is not NoComment:
+            self.yaml_key_comment_extend(key, comment)
+        else:
+            self.ca.comment = comment
+
+    def _yaml_add_eol_comment(self, comment, key):
+        # type: (Any, Any) -> None
+        self._yaml_add_comment(comment, key=key)
+
+    def _yaml_get_columnX(self, key):
         # type: (Any) -> Any
-        res = list.pop(self, idx)
-        self.ca.items.pop(idx, None)  # might not be there -> default value
-        for list_index in sorted(self.ca.items):
-            if list_index < idx:
-                continue
-            self.ca.items[list_index - 1] = self.ca.items.pop(list_index)
-        return res
+        return self.ca.items[key][0].start_mark.column
 
     def _yaml_get_column(self, key):
         # type: (Any) -> Any
@@ -461,18 +492,6 @@ class CommentedSeq(list, CommentedBase):
             self.copy_attributes(res, deep=True)
         return res
 
-    def __setitem__(self, idx, value):
-        # type: (Any, Any) -> None
-        # try to preserve the scalarstring type if setting an existing key to a new value
-        if idx < len(self):
-            if (
-                isinstance(value, string_types)
-                and not isinstance(value, ScalarString)
-                and isinstance(self[idx], ScalarString)
-            ):
-                value = type(self[idx])(value)
-        list.__setitem__(self, idx, value)
-
 
 class CommentedKeySeq(tuple, CommentedBase):
     """This primarily exists to be able to roundtrip keys that are sequences"""
diff --git a/compat.py b/compat.py
index c2db2bb..80cb089 100644
--- a/compat.py
+++ b/compat.py
@@ -91,7 +91,7 @@ if PY3:
     BytesIO = io.BytesIO
     # have unlimited precision
     no_limit_int = int
-    from collections.abc import Hashable  # NOQA
+    from collections.abc import Hashable, MutableSequence  # NOQA
 
 else:
     string_types = basestring  # NOQA
@@ -110,7 +110,7 @@ else:
     BytesIO = cStringIO.StringIO
     # have unlimited precision
     no_limit_int = long  # NOQA not available on Python 3
-    from collections import Hashable  # NOQA
+    from collections import Hashable, MutableSequence  # NOQA
 
 if False:  # MYPY
     # StreamType = Union[BinaryIO, IO[str], IO[unicode],  StringIO]
diff --git a/constructor.py b/constructor.py
index 8bf72bb..9de28d0 100644
--- a/constructor.py
+++ b/constructor.py
@@ -16,7 +16,8 @@ from ruamel.yaml.error import (MarkedYAMLError, MarkedYAMLFutureWarning,
 from ruamel.yaml.nodes import *                               # NOQA
 from ruamel.yaml.nodes import (SequenceNode, MappingNode, ScalarNode)
 from ruamel.yaml.compat import (utf8, builtins_module, to_str, PY2, PY3,  # NOQA
-                                ordereddict, text_type, nprint, version_tnf, Hashable)
+                                ordereddict, text_type, nprint, version_tnf, Hashable,
+                                MutableSequence)
 from ruamel.yaml.comments import *                               # NOQA
 from ruamel.yaml.comments import (CommentedMap, CommentedOrderedMap, CommentedSet,
                                   CommentedKeySeq, CommentedSeq, TaggedScalar)
@@ -1311,7 +1312,7 @@ class RoundTripConstructor(SafeConstructor):
             key = self.construct_object(key_node, deep=True)
             # lists are not hashable, but tuples are
             if not isinstance(key, Hashable):
-                if isinstance(key, list):
+                if isinstance(key, MutableSequence):
                     key_a = CommentedKeySeq(key)
                     if key_node.flow_style is True:
                         key_a.fa.set_flow_style()