Add to_json method for exporting Entry metadata to JSON

metacatalog/models/entry.py

@@ -18,6 +18,7 @@
 from uuid import uuid4
 import warnings
 from collections import defaultdict
+from decimal import Decimal
 
 from sqlalchemy import Column, ForeignKey, event
 from sqlalchemy import Integer, String, Boolean, DateTime
@@ -399,10 +400,41 @@ def from_dict(cls, session: Session, data: dict) -> 'Entry':
 
         return entry
 
+
     @classmethod
     def is_valid(cls, entry: 'Entry') -> bool:
         return isinstance(entry, Entry) and entry.id is not None
 
+
+    def to_json(self, path: str) -> None:
+        """
+        Exports the Entry metadata (from the to_dict method) to a serializable 
+        JSON.
+
+        .. versionadded:: 0.9.1
+
+        Parameters
+        ----------
+        path : str
+            Path to the file to write the JSON to.
+
+        """
+        # custom encoder for datetime and Decimal data types
+        class DictToSerializableJsonEncoder(json.JSONEncoder):
+            def default(self, obj):
+                if isinstance(obj, Decimal):
+                    return str(obj)
+                if isinstance(obj, dt):
+                    return obj.isoformat()
+                return super().default(obj)
+
+        # get the dict
+        entry_dict = self.to_dict()
+
+        # write
+        with open(path, 'w') as f:
+            json.dump(entry_dict, f, indent=4, cls=DictToSerializableJsonEncoder)
+
     @property
     def checksum(self) -> str:
         """

metacatalog/test/test_todict_fromdict.py

@@ -3,6 +3,7 @@
 from metacatalog import api
 from metacatalog.models import Entry
 from ._util import connect
+import json
 
 
 def check_to_dict_persons(session):
@@ -46,8 +47,37 @@ def check_from_dict(session):
     return True
 
 
+def check_to_json(session, tmp_path):
+    """
+    Check Entry.to_json().
+    This also checks if the output is a valid json by trying to load 
+    it with json.load().
+
+    """
+    # test for all entries in test database
+    for entry in api.find_entry(session):
+        # create a temporary file
+        tmp_file = tmp_path / "entry.json"
+
+        # write JSON to the temporary file
+        entry.to_json(path=str(tmp_file))
+
+        # load the JSON from the file, if the JSON is not valid, the test fails with a JSONDecodeError
+
+        with open(tmp_file, 'r') as f:
+            loaded_dict = json.load(f)
+
+    assert loaded_dict['title'] == entry.title
+    assert isinstance(loaded_dict['id'], int)
+    assert isinstance(loaded_dict['author'], dict)
+    assert isinstance(loaded_dict['authors'], list)
+    assert isinstance(loaded_dict['embargo'], bool)
+
+    return True
+
+
 @pytest.mark.depends(on=['add_find'], name='dict_methods')
-def test_fromdict_todict():
+def test_fromdict_todict(tmp_path):
     """
     Currently tests Entry.to_dict() and Entry.from_dict()
     """
@@ -75,3 +105,4 @@ def test_fromdict_todict():
     # run single tests
     assert check_to_dict_persons(session)
     assert check_from_dict(session)
+    assert check_to_json(session, tmp_path=tmp_path)