Add YAML 1.2 tags

Example code:

    import yaml

    class MyCoreLoader(yaml.BaseLoader): pass
    class MyJSONLoader(yaml.BaseLoader): pass
    class MyCoreDumper(yaml.CommonDumper): pass
    class MyJSONDumper(yaml.CommonDumper): pass

    MyCoreLoader.init_tags('core')
    MyJSONLoader.init_tags('json')

    MyCoreDumper.init_tags('core')
    MyJSONDumper.init_tags('json')

    input = """
    - TRUE
    - yes
    - ~
    - true
    #- .inf
    #- 23
    #- #empty
    #- !!str #empty
    #- 010
    #- 0o10
    #- 0b100
    #- 0x20
    #- -0x20
    #- 1_000
    #- 3:14
    #- 0011
    #- +0
    #- 0001.23
    #- !!str +0.3e3
    #- +0.3e3
    #- &x foo
    #- *x
    #- 1e27
    #- 1x+27
    """

    print('--------------------------------------------- BaseLoader')
    data = yaml.load(input, Loader=yaml.BaseLoader)
    print(data)
    print('--------------------------------------------- SafeLoader')
    data = yaml.load(input, Loader=yaml.SafeLoader)
    print(data)
    print('--------------------------------------------- CoreLoader')
    data = yaml.load(input, Loader=MyCoreLoader)
    print(data)
    print('--------------------------------------------- JSONLoader')
    data = yaml.load(input, Loader=MyJSONLoader)
    print(data)

    print('--------------------------------------------- SafeDumper')
    out = yaml.dump(data, Dumper=yaml.SafeDumper)
    print(out)
    print('--------------------------------------------- MyCoreDumper')
    out = yaml.dump(data, Dumper=MyCoreDumper)
    print(out)
    print('--------------------------------------------- MyJSONDumper')
    out = yaml.dump(data, Dumper=MyJSONDumper)
    print(out)

lib/yaml/dumper.py

@@ -1,5 +1,5 @@
 
-__all__ = ['BaseDumper', 'SafeDumper', 'Dumper']
+__all__ = ['BaseDumper', 'SafeDumper', 'Dumper', 'CommonDumper']
 
 from .emitter import *
 from .serializer import *
@@ -42,6 +42,29 @@ def __init__(self, stream,
                 default_flow_style=default_flow_style, sort_keys=sort_keys)
         Resolver.__init__(self)
 
+class CommonDumper(Emitter, Serializer, CommonRepresenter, BaseResolver):
+
+    def __init__(self, stream,
+            default_style=None, default_flow_style=False,
+            canonical=None, indent=None, width=None,
+            allow_unicode=None, line_break=None,
+            encoding=None, explicit_start=None, explicit_end=None,
+            version=None, tags=None, sort_keys=True):
+        Emitter.__init__(self, stream, canonical=canonical,
+                indent=indent, width=width,
+                allow_unicode=allow_unicode, line_break=line_break)
+        Serializer.__init__(self, encoding=encoding,
+                explicit_start=explicit_start, explicit_end=explicit_end,
+                version=version, tags=tags)
+        CommonRepresenter.__init__(self, default_style=default_style,
+                default_flow_style=default_flow_style, sort_keys=sort_keys)
+        BaseResolver.__init__(self)
+
+    @classmethod
+    def init_tags(cls, tagset):
+        cls.init_representers(tagset)
+        cls.init_resolvers(tagset)
+
 class Dumper(Emitter, Serializer, Representer, Resolver):
 
     def __init__(self, stream,

lib/yaml/loader.py

@@ -1,5 +1,6 @@
 
-__all__ = ['BaseLoader', 'FullLoader', 'SafeLoader', 'Loader', 'UnsafeLoader']
+__all__ = ['BaseLoader', 'FullLoader', 'SafeLoader', 'Loader', 'UnsafeLoader',
+  ]
 
 from .reader import *
 from .scanner import *
@@ -18,6 +19,11 @@ def __init__(self, stream):
         BaseConstructor.__init__(self)
         BaseResolver.__init__(self)
 
+    @classmethod
+    def init_tags(cls, tagset):
+        cls.init_constructors(tagset)
+        cls.init_resolvers(tagset)
+
 class FullLoader(Reader, Scanner, Parser, Composer, FullConstructor, Resolver):
 
     def __init__(self, stream):

lib/yaml/representer.py

@@ -1,6 +1,6 @@
 
 __all__ = ['BaseRepresenter', 'SafeRepresenter', 'Representer',
-    'RepresenterError']
+    'RepresenterError', 'CommonRepresenter']
 
 from .error import *
 from .nodes import *
@@ -131,29 +131,30 @@ def represent_mapping(self, tag, mapping, flow_style=None):
     def ignore_aliases(self, data):
         return False
 
-class SafeRepresenter(BaseRepresenter):
+    def represent_str(self, data):
+        return self.represent_scalar('tag:yaml.org,2002:str', data)
 
-    def ignore_aliases(self, data):
-        if data is None:
-            return True
-        if isinstance(data, tuple) and data == ():
-            return True
-        if isinstance(data, (str, bytes, bool, int, float)):
-            return True
+    def represent_list(self, data):
+        #pairs = (len(data) > 0 and isinstance(data, list))
+        #if pairs:
+        #    for item in data:
+        #        if not isinstance(item, tuple) or len(item) != 2:
+        #            pairs = False
+        #            break
+        #if not pairs:
+            return self.represent_sequence('tag:yaml.org,2002:seq', data)
+        #value = []
+        #for item_key, item_value in data:
+        #    value.append(self.represent_mapping(u'tag:yaml.org,2002:map',
+        #        [(item_key, item_value)]))
+        #return SequenceNode(u'tag:yaml.org,2002:pairs', value)
+
+    def represent_dict(self, data):
+        return self.represent_mapping('tag:yaml.org,2002:map', data)
 
     def represent_none(self, data):
         return self.represent_scalar('tag:yaml.org,2002:null', 'null')
 
-    def represent_str(self, data):
-        return self.represent_scalar('tag:yaml.org,2002:str', data)
-
-    def represent_binary(self, data):
-        if hasattr(base64, 'encodebytes'):
-            data = base64.encodebytes(data).decode('ascii')
-        else:
-            data = base64.encodestring(data).decode('ascii')
-        return self.represent_scalar('tag:yaml.org,2002:binary', data, style='|')
-
     def represent_bool(self, data):
         if data:
             value = 'true'
@@ -184,27 +185,17 @@ def represent_float(self, data):
             # Unfortunately, this is not a valid float representation according
             # to the definition of the `!!float` tag.  We fix this by adding
             # '.0' before the 'e' symbol.
+            # TODO (In YAML 1.2 Core, 1e17 would be a valid float though)
             if '.' not in value and 'e' in value:
                 value = value.replace('e', '.0e', 1)
         return self.represent_scalar('tag:yaml.org,2002:float', value)
 
-    def represent_list(self, data):
-        #pairs = (len(data) > 0 and isinstance(data, list))
-        #if pairs:
-        #    for item in data:
-        #        if not isinstance(item, tuple) or len(item) != 2:
-        #            pairs = False
-        #            break
-        #if not pairs:
-            return self.represent_sequence('tag:yaml.org,2002:seq', data)
-        #value = []
-        #for item_key, item_value in data:
-        #    value.append(self.represent_mapping(u'tag:yaml.org,2002:map',
-        #        [(item_key, item_value)]))
-        #return SequenceNode(u'tag:yaml.org,2002:pairs', value)
-
-    def represent_dict(self, data):
-        return self.represent_mapping('tag:yaml.org,2002:map', data)
+    def represent_binary(self, data):
+        if hasattr(base64, 'encodebytes'):
+            data = base64.encodebytes(data).decode('ascii')
+        else:
+            data = base64.encodestring(data).decode('ascii')
+        return self.represent_scalar('tag:yaml.org,2002:binary', data, style='|')
 
     def represent_set(self, data):
         value = {}
@@ -220,54 +211,91 @@ def represent_datetime(self, data):
         value = data.isoformat(' ')
         return self.represent_scalar('tag:yaml.org,2002:timestamp', value)
 
-    def represent_yaml_object(self, tag, data, cls, flow_style=None):
-        if hasattr(data, '__getstate__'):
-            state = data.__getstate__()
-        else:
-            state = data.__dict__.copy()
-        return self.represent_mapping(tag, state, flow_style=flow_style)
-
     def represent_undefined(self, data):
         raise RepresenterError("cannot represent an object", data)
 
-SafeRepresenter.add_representer(type(None),
-        SafeRepresenter.represent_none)
-
-SafeRepresenter.add_representer(str,
-        SafeRepresenter.represent_str)
-
-SafeRepresenter.add_representer(bytes,
-        SafeRepresenter.represent_binary)
-
-SafeRepresenter.add_representer(bool,
-        SafeRepresenter.represent_bool)
-
-SafeRepresenter.add_representer(int,
-        SafeRepresenter.represent_int)
-
-SafeRepresenter.add_representer(float,
-        SafeRepresenter.represent_float)
+    @classmethod
+    def init_representers(cls, name):
+        for key in _representers[name]:
+            callback = _representers[name][key]
+            cls.add_representer(key, callback)
 
-SafeRepresenter.add_representer(list,
-        SafeRepresenter.represent_list)
+class CommonRepresenter(BaseRepresenter):
 
-SafeRepresenter.add_representer(tuple,
-        SafeRepresenter.represent_list)
+    def ignore_aliases(self, data):
+        if data is None:
+            return True
+        if isinstance(data, tuple) and data == ():
+            return True
+        if isinstance(data, (str, bytes, bool, int, float)):
+            return True
 
-SafeRepresenter.add_representer(dict,
-        SafeRepresenter.represent_dict)
+    def represent_yaml_object(self, tag, data, cls, flow_style=None):
+        if hasattr(data, '__getstate__'):
+            state = data.__getstate__()
+        else:
+            state = data.__dict__.copy()
+        return self.represent_mapping(tag, state, flow_style=flow_style)
 
-SafeRepresenter.add_representer(set,
-        SafeRepresenter.represent_set)
+class SafeRepresenter(BaseRepresenter):
 
-SafeRepresenter.add_representer(datetime.date,
-        SafeRepresenter.represent_date)
+    def ignore_aliases(self, data):
+        if data is None:
+            return True
+        if isinstance(data, tuple) and data == ():
+            return True
+        if isinstance(data, (str, bytes, bool, int, float)):
+            return True
 
-SafeRepresenter.add_representer(datetime.datetime,
-        SafeRepresenter.represent_datetime)
+    def represent_yaml_object(self, tag, data, cls, flow_style=None):
+        if hasattr(data, '__getstate__'):
+            state = data.__getstate__()
+        else:
+            state = data.__dict__.copy()
+        return self.represent_mapping(tag, state, flow_style=flow_style)
 
-SafeRepresenter.add_representer(None,
-        SafeRepresenter.represent_undefined)
+_representers = {
+    'yaml11': {
+        bool: BaseRepresenter.represent_bool,
+        dict: BaseRepresenter.represent_dict,
+        list: BaseRepresenter.represent_list,
+        tuple: BaseRepresenter.represent_list,
+        str: BaseRepresenter.represent_str,
+        float: BaseRepresenter.represent_float,
+        int: BaseRepresenter.represent_int,
+        type(None): BaseRepresenter.represent_none,
+        bytes: BaseRepresenter.represent_binary,
+        set: BaseRepresenter.represent_set,
+        datetime.date: BaseRepresenter.represent_date,
+        datetime.datetime: BaseRepresenter.represent_datetime,
+        None: BaseRepresenter.represent_undefined,
+    },
+    'core': {
+        bool: BaseRepresenter.represent_bool,
+        dict: BaseRepresenter.represent_dict,
+        list: BaseRepresenter.represent_list,
+        tuple: BaseRepresenter.represent_list,
+        str: BaseRepresenter.represent_str,
+        float: BaseRepresenter.represent_float,
+        int: BaseRepresenter.represent_int,
+        type(None): BaseRepresenter.represent_none,
+        None: BaseRepresenter.represent_undefined,
+    },
+    'json': {
+        bool: BaseRepresenter.represent_bool,
+        dict: BaseRepresenter.represent_dict,
+        list: BaseRepresenter.represent_list,
+        tuple: BaseRepresenter.represent_list,
+        str: BaseRepresenter.represent_str,
+        float: BaseRepresenter.represent_float,
+        int: BaseRepresenter.represent_int,
+        type(None): BaseRepresenter.represent_none,
+        None: BaseRepresenter.represent_undefined,
+    },
+}
+
+
+SafeRepresenter.init_representers('yaml11')
 
 class Representer(SafeRepresenter):