Draft: ENH: file system: link

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• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md (or not necessary)
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src/linkahead/common/models.py

@@ -119,6 +119,7 @@ class Entity:
         self.parents = _ParentList()
         self.path = None
         self.file = None
+        self.link_target = None
         self.unit = None
         self.acl = None
         self.permissions = None
@@ -305,6 +306,17 @@ class Entity:
     def path(self, new_path):
         self.__path = new_path
 
+    @property
+    def link_target(self):
+        if self.__link_target is not None or self._wrapped_entity is None:
+            return self.__link_target
+
+        return self._wrapped_entity.link_target
+
+    @link_target.setter
+    def link_target(self, new_link_target):
+        self.__link_target = new_link_target
+
     @property
     def thumbnail(self):
         warn(DeprecationWarning(
@@ -1231,6 +1243,9 @@ out: List[Entity]
         if self.file is not None and local_serialization:
             xml.set("file", self.file)
 
+        if self.link_target is not None:
+            xml.set("linktarget", str(self.link_target))
+
         if self.checksum is not None:
             xml.set("checksum", self.checksum)
 
@@ -1285,6 +1300,7 @@ out: List[Entity]
         entity.description = elem.get("description")
         entity.path = elem.get("path")
         entity._checksum = elem.get("checksum")
+        entity.link_target = elem.get("linktarget")
         entity._size = elem.get("size")
         entity.datatype = elem.get("datatype")  # @ReservedAssignment
         entity.unit = elem.get("unit")
@@ -1566,7 +1582,7 @@ def _parse_value(datatype, value):
 
     # This is for a special case, where the xml parser could not differentiate
     # between single values and lists with one element. As
-    if hasattr(value, "__len__") and len(value) == 1:
+    if hasattr(value, "__len__") and len(value) == 1 and not isinstance(value, str):
         return _parse_value(datatype, value[0])
 
     # deal with references
@@ -2011,6 +2027,39 @@ class Record(Entity):
         return Entity.to_xml(self, xml, add_properties=ALL)
 
 
+class Link(Record):
+    """This class represents LinkAheads's link entities."""
+
+    def __init__(self, name=None, id=None, description=None, path=None,
+                 target=None):
+        Record.__init__(self, id=id, name=name, description=description)
+        self.role = "Link"
+        self.datatype = None
+        self.link_target = target
+
+        # location in the fileserver
+        self.path = path
+
+    def to_xml(self, xml=None, add_properties=ALL, local_serialization=False):
+        """Convert this Link to an xml element.
+
+        @return: xml element
+        """
+
+        if xml is None:
+            xml = etree.Element("Link")
+
+        return Entity.to_xml(self, xml=xml, add_properties=add_properties,
+                             local_serialization=local_serialization)
+
+    def add_property(self, property=None, id=None, name=None, description=None, datatype=None,
+                     value=None, unit=None, importance=FIX, inheritance=FIX):
+
+        return super().add_property(
+            property=property, id=id, name=name, description=description, datatype=datatype,
+            value=value, unit=unit, importance=importance, inheritance=inheritance)
+
+
 class Directory(Record):
     """This class represents CaosDB's directory entities."""
 
@@ -2699,30 +2748,13 @@ def _basic_sync(e_local, e_remote):
                          "this client did't know about it yet.".format(
                              e_remote.role, e_local.role))
 
-    e_local.id = e_remote.id
-    e_local.name = e_remote.name
-    e_local.description = e_remote.description
-    e_local.path = e_remote.path
-    e_local._checksum = e_remote._checksum
-    e_local._size = e_remote._size
-    e_local.datatype = e_remote.datatype
-    e_local.unit = e_remote.unit
-    e_local.value = e_remote.value
-    e_local.properties = e_remote.properties
-    e_local.parents = e_remote.parents
-    e_local.messages = e_remote.messages
-    e_local.acl = e_remote.acl
-    e_local.permissions = e_remote.permissions
-    e_local.is_valid = e_remote.is_valid
-    e_local.is_deleted = e_remote.is_deleted
-    e_local.version = e_remote.version
-    e_local.state = e_remote.state
-
-    if hasattr(e_remote, "query"):
-        e_local.query = e_remote.query
-
-    if hasattr(e_remote, "affiliation"):
-        e_local.affiliation = e_remote.affiliation
+    for attr in ["path", "link_target", "_checksum", "_size", "datatype",
+                 "unit", "value", "properties", "parents", "messages", "acl",
+                 "permissions", "is_valid", "is_deleted", "version", "state",
+                 "query", "affiliation", "id", "name", "description"]:
+
+        if hasattr(e_remote, attr):
+            setattr(e_local, attr, getattr(e_remote, attr))
 
     return e_local
 
@@ -3216,6 +3248,7 @@ class Container(list):
 
         for local_entity in self:
             if (sync_dict[local_entity] is None
+                    and hasattr(local_entity, "path")
                     and local_entity.path is not None):
                 sync_remote_entities = []
 
@@ -4717,6 +4750,7 @@ def _parse_single_xml_element(elem):
         'property': Property,
         'file': File,
         'directory': Directory,
+        'link': Link,
         'parent': Parent,
         'entity': Entity}