Link.to_dict() should only contain strings

CHANGELOG.md

@@ -19,6 +19,7 @@
 - Use `pyproject.toml` instead of `setup.py` ([#1100](https://github.com/stac-utils/pystac/pull/1100))
 - `DefaultStacIO` now raises an error if it tries to write to a non-local url ([#1107](https://github.com/stac-utils/pystac/pull/1107))
 - Allow instantiation of pystac objects even with `"stac_extensions": null` ([#1109](https://github.com/stac-utils/pystac/pull/1109))
+- Make `Link.to_dict()` only contain strings ([#1114](https://github.com/stac-utils/pystac/pull/1114))
 
 ### Deprecated
 

pystac/link.py

@@ -67,7 +67,7 @@ class Link(PathLike):
     """The relation of the link (e.g. 'child', 'item'). Registered rel Types are
     preferred. See :class:`~pystac.RelType` for common media types."""
 
-    media_type: Optional[str]
+    media_type: Optional[Union[str, pystac.MediaType]]
     """Optional description of the media type. Registered Media Types are preferred.
     See :class:`~pystac.MediaType` for common media types."""
 
@@ -88,7 +88,7 @@ def __init__(
         self,
         rel: Union[str, pystac.RelType],
         target: Union[str, STACObject],
-        media_type: Optional[str] = None,
+        media_type: Optional[Union[str, pystac.MediaType]] = None,
         title: Optional[str] = None,
         extra_fields: Optional[Dict[str, Any]] = None,
     ) -> None:
@@ -372,12 +372,12 @@ def to_dict(self, transform_href: bool = True) -> Dict[str, Any]:
         """
 
         d: Dict[str, Any] = {
-            "rel": self.rel,
+            "rel": str(self.rel),
             "href": self.get_href(transform_href=transform_href),
         }
 
         if self.media_type is not None:
-            d["type"] = self.media_type
+            d["type"] = str(self.media_type)
 
         if self.title is not None:
             d["title"] = self.title

tests/test_link.py

@@ -205,8 +205,8 @@ def test_serialize_link(self) -> None:
         link = pystac.Link(pystac.RelType.SELF, href, pystac.MediaType.JSON, title)
         link_dict = link.to_dict()
 
-        self.assertEqual(str(link_dict["rel"]), "self")
-        self.assertEqual(str(link_dict["type"]), "application/json")
+        self.assertEqual(link_dict["rel"], "self")
+        self.assertEqual(link_dict["type"], "application/json")
         self.assertEqual(link_dict["title"], title)
         self.assertEqual(link_dict["href"], href)