round-trip support for tagged scalars0.15.33

Inspired by Matthew Patton's question on StackOverflow:
https://stackoverflow.com/a/45967047/1307905

8 files changed, 84 insertions, 33 deletions

diff --git a/CHANGES b/CHANGES
index ff8f432..8d8d2f0 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,10 @@
+[0, 15, 33]: 2017-08-31
+  - support for "undefined" round-tripping tagged scalar objects (in addition to
+    tagged mapping object). Inspired by a use case presented by Matthew Patton
+    on `StackOverflow <https://stackoverflow.com/a/45967047/1307905>`__.
+  - fix issue 148: replace cryptic error message when using !!timestamp with an
+    incorrectly formatted or non- scalar. Reported by FichteFoll.
+
 [0, 15, 32]: 2017-08-21
   - allow setting ``yaml.default_flow_style = None`` (default: ``False``) for
     for ``typ='rt'``.
diff --git a/README.rst b/README.rst
index 7cd8333..b1a0024 100644
--- a/README.rst
+++ b/README.rst
@@ -35,17 +35,25 @@ ChangeLog
 
 .. should insert NEXT: at the beginning of line for next key
 
+0.15.33 (2017-08-31):
+  - support for "undefined" round-tripping tagged scalar objects (in addition to
+    tagged mapping object). Inspired by a use case presented by Matthew Patton
+    on `StackOverflow <https://stackoverflow.com/a/45967047/1307905>`__.
+  - fix issue 148: replace cryptic error message when using !!timestamp with an
+    incorrectly formatted or non- scalar. Reported by FichteFoll.
+
 0.15.32 (2017-08-21):
   - allow setting ``yaml.default_flow_style = None`` (default: ``False``) for
     for ``typ='rt'``.
   - fix for issue 149: multiplications on ``ScalarFloat`` now return ``float``
+    (reported by jan.brezina@tul.cz)
 
 0.15.31 (2017-08-15):
   - fix Comment dumping
 
 0.15.30 (2017-08-14):
   - fix for issue with "compact JSON" not parsing: ``{"in":{},"out":{}}``
-    (reported on `StackOverflow <https://stackoverflow.com/q/45681626/1307905>`_ by
+    (reported on `StackOverflow <https://stackoverflow.com/q/45681626/1307905>`__ by
     `mjalkio <https://stackoverflow.com/users/5130525/mjalkio>`_
 
 0.15.29 (2017-08-14):
@@ -74,7 +82,7 @@ ChangeLog
     42.00E+56, 0.0, -0.0 etc. while keeping the format. Underscores in mantissas
     are not preserved/supported (yet, is anybody using that?).
   - (finally) fixed longstanding issue 23 (reported by `Antony Sottile
-    <https://bitbucket.org/asottile/>`_), now handling comment between block
+    <https://bitbucket.org/asottile/>`__), now handling comment between block
     mapping key and value correctly
   - warn on YAML 1.1 float input that is incorrect (triggered by invalid YAML
     provided by Cecil Curry)
@@ -102,28 +110,28 @@ ChangeLog
 0.15.18 (2017-07-04):
   - missing ``pure`` attribute on ``YAML`` useful for implementing `!include` tag
     constructor for `including YAML files in a YAML file
-    <https://stackoverflow.com/a/44913652/1307905>`_
+    <https://stackoverflow.com/a/44913652/1307905>`__
   - some documentation improvements
   - trigger of doc build on new revision
 
 0.15.17 (2017-07-03):
   - support for Unicode supplementary Plane **output**
     (input was already supported, triggered by
-    `this <https://stackoverflow.com/a/44875714/1307905>`_ Stack Overflow Q&A)
+    `this <https://stackoverflow.com/a/44875714/1307905>`__ Stack Overflow Q&A)
 
 0.15.16 (2017-07-01):
   - minor typing issues (reported and fix provided by
-    `Manvendra Singh <https://bitbucket.org/manu-chroma/>`_
+    `Manvendra Singh <https://bitbucket.org/manu-chroma/>`__
   - small doc improvements
 
 0.15.15 (2017-06-27):
   - fix for issue 135, typ='safe' not dumping in Python 2.7
-    (reported by Andrzej Ostrowski <https://bitbucket.org/aostr123/>`_)
+    (reported by Andrzej Ostrowski <https://bitbucket.org/aostr123/>`__)
 
 0.15.14 (2017-06-25):
   - fix for issue 133, in setup.py: change ModuleNotFoundError to
     ImportError (reported and fix by
-    `Asley Drake  <https://github.com/aldraco>`_)
+    `Asley Drake  <https://github.com/aldraco>`__)
 
 0.15.13 (2017-06-24):
   - suppress duplicate key warning on mappings with merge keys (reported by
@@ -135,7 +143,7 @@ ChangeLog
 
 0.15.11 (2017-06-24):
   - fix for issue 130, regression in nested merge keys (reported by
-    `David Fee <https://bitbucket.org/dfee/>`_)
+    `David Fee <https://bitbucket.org/dfee/>`__)
 
 0.15.10 (2017-06-23):
   - top level PreservedScalarString not indented if not explicitly asked to
@@ -145,7 +153,7 @@ ChangeLog
 0.15.9 (2017-06-16):
   - fix for issue 127: tagged scalars were always quoted and seperated
     by a newline when in a block sequence (reported and largely fixed by
-    `Tommy Wang <https://bitbucket.org/twang817/>`_)
+    `Tommy Wang <https://bitbucket.org/twang817/>`__)
 
 0.15.8 (2017-06-15):
   - allow plug-in install via ``install ruamel.yaml[jinja2]``
@@ -175,7 +183,7 @@ ChangeLog
   - update to conform to mypy 0.511: mypy --strict
 
 0.15.1 (2017-06-07):
-  - `duplicate keys  <http://yaml.readthedocs.io/en/latest/api.html#duplicate-keys>`_
+  - `duplicate keys  <http://yaml.readthedocs.io/en/latest/api.html#duplicate-keys>`__
     in mappings generate an error (in the old API this change generates a warning until 0.16)
   - dependecy on ruamel.ordereddict for 2.7 now via extras_require
 
@@ -206,7 +214,7 @@ ChangeLog
 
 0.14.8 (2017-04-19):
   - fix Text not available on 3.5.0 and 3.5.1, now proactively setting version guards
-    on all files (reported by `João Paulo Magalhães <https://bitbucket.org/jpmag/>`_)
+    on all files (reported by `João Paulo Magalhães <https://bitbucket.org/jpmag/>`__)
 
 0.14.7 (2017-04-18):
   - round trip of integers (decimal, octal, hex, binary) now preserve
@@ -233,8 +241,8 @@ ChangeLog
 
 0.14.3 (2017-03-31):
   - fix for 0o52 not being a string in YAML 1.1 (reported on
-    `StackOverflow Q&A 43138503 <http://stackoverflow.com/a/43138503/1307905>`_ by
-    `Frank D <http://stackoverflow.com/users/7796630/frank-d>`_)
+    `StackOverflow Q&A 43138503 <http://stackoverflow.com/a/43138503/1307905>`__ by
+    `Frank D <http://stackoverflow.com/users/7796630/frank-d>`__)
 
 0.14.2 (2017-03-23):
   - fix for old default pip on Ubuntu 14.04 (reported by Sébastien Maccagnoni-Munch)
diff --git a/__init__.py b/__init__.py
index a90d9d2..0a8148e 100644
--- a/__init__.py
+++ b/__init__.py
@@ -7,8 +7,8 @@ if False:  # MYPY
 
 _package_data = dict(
     full_package_name='ruamel.yaml',
-    version_info=(0, 15, 32),
-    __version__='0.15.32',
+    version_info=(0, 15, 33),
+    __version__='0.15.33',
     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/_doc/basicuse.ryd b/_doc/basicuse.ryd
index 6488fe2..36da2d4 100644
--- a/_doc/basicuse.ryd
+++ b/_doc/basicuse.ryd
@@ -26,7 +26,7 @@ You load a YAML document using::
 --- !python |
 from ruamel.yaml import YAML
 
-yaml=YAML(typ='safe')   # default if not specfied is round-trip
+yaml=YAML(typ='safe')   # default, if not specfied, is 'rt' (round-trip)
 yaml.load(doc)
 
 --- |
diff --git a/_test/test_tag.py b/_test/test_tag.py
index fc8a4bd..2117ff4 100644
--- a/_test/test_tag.py
+++ b/_test/test_tag.py
@@ -94,3 +94,13 @@ class TestRoundTripCustom:
           location: Germany
           language: python
         """)
+
+    def test_scalar_00(self):
+        # https://stackoverflow.com/a/45967047/1307905
+        round_trip("""\
+        Outputs:
+          Vpc:
+            Value: !Ref: vpc    # first tag
+            Export:
+              Name: !Sub "${AWS::StackName}-Vpc"  # second tag
+        """)
diff --git a/comments.py b/comments.py
index d77b981..49fd9f4 100644
--- a/comments.py
+++ b/comments.py
@@ -943,6 +943,12 @@ class CommentedSet(MutableSet, CommentedMap):
         return 'set({0!r})'.format(self.odict.keys())
 
 
+class TaggedScalar(CommentedBase):
+    # the value and style attributes are set during roundtrip construction
+    def __str__(self):
+        return self.value
+
+
 def dump_comments(d, name='', sep='.', out=sys.stdout):
     # type: (Any, str, str, Any) -> None
     """
diff --git a/constructor.py b/constructor.py
index c77d11c..9706bbe 100644
--- a/constructor.py
+++ b/constructor.py
@@ -19,7 +19,7 @@ from ruamel.yaml.compat import (utf8, builtins_module, to_str, PY2, PY3,  # NOQA
                                 ordereddict, text_type, nprint, version_tnf)
 from ruamel.yaml.comments import *                               # NOQA
 from ruamel.yaml.comments import (CommentedMap, CommentedOrderedMap, CommentedSet,
-                                  CommentedKeySeq, CommentedSeq)
+                                  CommentedKeySeq, CommentedSeq, TaggedScalar)
 from ruamel.yaml.scalarstring import *                           # NOQA
 from ruamel.yaml.scalarstring import (PreservedScalarString, SingleQuotedScalarString,
                                       DoubleQuotedScalarString, ScalarString)
@@ -1419,21 +1419,31 @@ class RoundTripConstructor(SafeConstructor):
     def construct_undefined(self, node):
         # type: (Any) -> Any
         try:
-            data = CommentedMap()
-            data._yaml_set_line_col(node.start_mark.line, node.start_mark.column)
-            if node.flow_style is True:
-                data.fa.set_flow_style()
-            elif node.flow_style is False:
-                data.fa.set_block_style()
-            data.yaml_set_tag(node.tag)
-            yield data
-            self.construct_mapping(node, data)
+            if isinstance(node, MappingNode):
+                data = CommentedMap()
+                data._yaml_set_line_col(node.start_mark.line, node.start_mark.column)
+                if node.flow_style is True:
+                    data.fa.set_flow_style()
+                elif node.flow_style is False:
+                    data.fa.set_block_style()
+                data.yaml_set_tag(node.tag)
+                yield data
+                self.construct_mapping(node, data)
+                return
+            elif isinstance(node, ScalarNode):
+                data = TaggedScalar()
+                data.value = self.construct_scalar(node)
+                data.style = node.style
+                data.yaml_set_tag(node.tag)
+                yield data
+                return
         except:
-            raise ConstructorError(
-                None, None,
-                "could not determine a constructor for the tag %r" %
-                utf8(node.tag),
-                node.start_mark)
+            pass
+        raise ConstructorError(
+            None, None,
+            "could not determine a constructor for the tag %r" %
+            utf8(node.tag),
+            node.start_mark)
 
     def construct_yaml_timestamp(self, node, values=None):
         # type: (Any, Any) -> Any
diff --git a/representer.py b/representer.py
index 70746bc..085308c 100644
--- a/representer.py
+++ b/representer.py
@@ -642,8 +642,8 @@ Representer.add_multi_representer(object,
                                   Representer.represent_object)
 
 
-from ruamel.yaml.comments import CommentedMap, CommentedOrderedMap, CommentedSeq, \
-    CommentedKeySeq, CommentedSet, comment_attrib, merge_attrib    # NOQA
+from ruamel.yaml.comments import (CommentedMap, CommentedOrderedMap, CommentedSeq,
+    CommentedKeySeq, CommentedSet, comment_attrib, merge_attrib, TaggedScalar)    # NOQA
 
 
 class RoundTripRepresenter(SafeRepresenter):
@@ -1096,6 +1096,13 @@ class RoundTripRepresenter(SafeRepresenter):
             value += _yaml['tz']
         return self.represent_scalar(u'tag:yaml.org,2002:timestamp', to_unicode(value))
 
+    def represent_tagged_scalar(self, data):
+        try:
+            tag = data.tag.value
+        except AttributeError:
+            tag = None
+        return self.represent_scalar(tag, data.value, style=data.style)
+
 
 RoundTripRepresenter.add_representer(type(None),
                                      RoundTripRepresenter.represent_none)
@@ -1153,5 +1160,8 @@ if sys.version_info >= (2, 7):
 RoundTripRepresenter.add_representer(CommentedSet,
                                      RoundTripRepresenter.represent_set)
 
+RoundTripRepresenter.add_representer(TaggedScalar,
+                                     RoundTripRepresenter.represent_tagged_scalar)
+
 RoundTripRepresenter.add_representer(TimeStamp,
                                      RoundTripRepresenter.represent_datetime)