preserve value type, support pathlib.Path as stream

6 files changed, 49 insertions, 7 deletions

diff --git a/README.rst b/README.rst
index b4c3c3e..e97288e 100644
--- a/README.rst
+++ b/README.rst
@@ -18,6 +18,14 @@ ChangeLog
 
 .. should insert NEXT: at the beginning of line for next key
 
+NEXT:
+  - it is no allowed to pass in a ``pathlib.Path`` as "stream" parameter to all
+    load/dump functions
+  - passing in a non-supported object (e.g. a string) as "stream" will result in a
+    much more meaningful YAMLStreamError.
+  - assigning a normal string value to an existing CommentedMap key or CommentedSeq
+    element will result in a value cast to the previous value's type if possible.
+
 0.14.12 (2017-05-14):
   - fix for issue 119, deepcopy not returning subclasses (reported and PR by
     Constantine Evans <cevans@evanslabs.org>)
diff --git a/__init__.py b/__init__.py
index 64e093c..e33f19e 100644
--- a/__init__.py
+++ b/__init__.py
@@ -11,8 +11,8 @@ if False:  # MYPY
 
 _package_data = dict(
     full_package_name='ruamel.yaml',
-    version_info=(0, 14, 12),
-    __version__='0.14.12',
+    version_info=(0, 14, 13, 'dev'),
+    __version__='0.14.13.dev',
     author='Anthon van der Neut',
     author_email='a.van.der.neut@ruamel.eu',
     description='ruamel.yaml is a YAML parser/emitter that supports roundtrip preservation of comments, seq/map flow style, and map key order',  # NOQA
diff --git a/comments.py b/comments.py
index 6bee2ac..93974d9 100644
--- a/comments.py
+++ b/comments.py
@@ -12,7 +12,8 @@ import copy
 
 from collections import MutableSet, Sized, Set
 
-from ruamel.yaml.compat import ordereddict, PY2
+from ruamel.yaml.compat import ordereddict, PY2, string_types
+from ruamel.yaml.scalarstring import ScalarString
 
 if False:  # MYPY
     from typing import Any, Dict, Optional, List, Union  # NOQA
@@ -435,6 +436,16 @@ 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"""
@@ -684,6 +695,16 @@ class CommentedMap(ordereddict, CommentedBase):
                     return merged[1][key]
             raise
 
+    def __setitem__(self, key, value):
+        # type: (Any, Any) -> None
+        # try to preserve the scalarstring type if setting an existing key to a new value
+        if key in self:
+            if isinstance(value, string_types) and \
+               not isinstance(value, ScalarString) and \
+               isinstance(self[key], ScalarString):
+                value = type(self[key])(value)
+        ordereddict.__setitem__(self, key, value)
+
     def _unmerged_contains(self, key):
         # type: (Any) -> Any
         if ordereddict.__contains__(self, key):
diff --git a/emitter.py b/emitter.py
index 44dfe05..773058a 100644
--- a/emitter.py
+++ b/emitter.py
@@ -10,7 +10,7 @@ from __future__ import print_function
 # sequence ::= SEQUENCE-START node* SEQUENCE-END
 # mapping ::= MAPPING-START (node node)* MAPPING-END
 
-from ruamel.yaml.error import YAMLError
+from ruamel.yaml.error import YAMLError, YAMLStreamError
 from ruamel.yaml.events import *                                     # NOQA
 from ruamel.yaml.compat import utf8, text_type, PY2, nprint, dbg, DBG_EVENT, \
     check_anchorname_char
@@ -58,7 +58,12 @@ class Emitter(object):
         if self.dumper is not None:
             self.dumper._emitter = self
         # The stream should have the methods `write` and possibly `flush`.
-        self.stream = stream
+        if not hasattr(stream, 'write') and hasattr(stream, 'open'):
+            self.stream = stream.open('w')  # pathlib.Path() instance
+        else:
+            if not hasattr(stream, 'write'):
+                raise YAMLStreamError('stream argument needs to have a write() method')
+            self.stream = stream
 
         # Encoding can be overriden by STREAM-START.
         self.encoding = None  # type: Union[None, Text]
diff --git a/error.py b/error.py
index 65a7a97..910e13b 100644
--- a/error.py
+++ b/error.py
@@ -126,6 +126,9 @@ class MarkedYAMLError(YAMLError):
         return '\n'.join(lines)
 
 
+class YAMLStreamError(Exception):
+    pass
+
 class ReusedAnchorWarning(Warning):
     pass
 
diff --git a/reader.py b/reader.py
index 2ececae..4cc67b8 100644
--- a/reader.py
+++ b/reader.py
@@ -23,7 +23,7 @@ from __future__ import absolute_import
 import codecs
 import re
 
-from ruamel.yaml.error import YAMLError, FileMark, StringMark
+from ruamel.yaml.error import YAMLError, FileMark, StringMark, YAMLStreamError
 from ruamel.yaml.compat import text_type, binary_type, PY3
 
 if False:  # MYPY
@@ -97,7 +97,12 @@ class Reader(object):
             self.raw_buffer = stream
             self.determine_encoding()
         else:
-            self.stream = stream
+            if not hasattr(stream, 'read') and hasattr(stream, 'open'):
+                self.stream = stream.open('r')
+            else:
+                if not hasattr(stream, 'read'):
+                    raise YAMLStreamError('stream argument needs to have a read() method')
+                self.stream = stream
             self.name = getattr(stream, 'name', "<file>")
             self.eof = False
             self.raw_buffer = None