[IMPR] Check whether Claim exists within Claim.fromJSON() method

- If a Claim type is not given to the initializer, the type is fetched
  from wikibase. This can fail if it does not exist. Try to get the
  type and if NoWikibaseEntityError write a warning instead raising
  a KeyError
- add a new exists() method to Property class
- raise NoWikibaseEntityError in Property.type property instead of
  KeyError

Bug: T374681
Change-Id: Id9047cfe688c9a13c9ccc4c4ee1aebe5628abe4c

pywikibot/page/_wikibase.py

@@ -1428,11 +1428,34 @@ def __init__(self, site, id: str, datatype: str | None = None) -> None:
         if datatype:
             self._type = datatype
 
+    def exists(self):
+        """Determine if the property exists in the data repository.
+
+        .. versionadded:: 9.4
+        """
+        try:
+            self._type = self.repo.getPropertyType(self)
+        except KeyError:
+            return False
+        return True
+
     @property
     @cached
     def type(self) -> str:
-        """Return the type of this property."""
-        return self.repo.getPropertyType(self)
+        """Return the type of this property.
+
+        .. versionchanged:: 9.4
+           raises :exc:`NoWikibaseEntityError` if property does not
+           exist.
+
+        :raises NoWikibaseEntityError: property does not exist
+        """
+        try:
+            prop_type = self.repo.getPropertyType(self)
+        except KeyError as e:
+            raise NoWikibaseEntityError(e)
+
+        return prop_type
 
     def getID(self, numeric: bool = False):
         """
@@ -1727,14 +1750,14 @@ def copy(self):
         return copy
 
     @classmethod
-    def fromJSON(cls, site, data):
-        """
-        Create a claim object from JSON returned in the API call.
+    def fromJSON(cls, site, data: dict[str, Any]) -> Claim:
+        """Create a claim object from JSON returned in the API call.
 
-        :param data: JSON containing claim data
-        :type data: dict
+        .. versionchanged:: 9.4
+           print a warning if the Claim.type is not given and missing in
+           the wikibase.
 
-        :rtype: pywikibot.page.Claim
+        :param data: JSON containing claim data
         """
         claim_repo = site.get_repo_for_entity_type('property')
         claim = cls(claim_repo, data['mainsnak']['property'],
@@ -1743,17 +1766,31 @@ def fromJSON(cls, site, data):
             claim.snak = data['id']
         elif 'hash' in data:
             claim.hash = data['hash']
+
         claim.snaktype = data['mainsnak']['snaktype']
         if claim.getSnakType() == 'value':
             value = data['mainsnak']['datavalue']['value']
-            # The default covers string, url types
-            if claim.type in cls.types:
+
+            # note: claim.type could be set during claim initialization
+            try:
+                claim_type = claim.type
+            except NoWikibaseEntityError:
+                claim_type = None
+
+            claim.target = None
+            if not claim_type:
+                pywikibot.warning(f'{claim.id} does not exist.')
+            elif claim.type in cls.types:
+                # The default covers string, url types
                 claim.target = cls.TARGET_CONVERTER.get(
                     claim.type, lambda value, site: value)(value, site)
             else:
                 pywikibot.warning(
                     f'{claim.type} datatype is not supported yet.')
+
+            if claim.target is None:
                 claim.target = pywikibot.WbUnknown.fromWikibase(value)
+
         if 'rank' in data:  # References/Qualifiers don't have ranks
             claim.rank = data['rank']
         if 'references' in data: