Fix item field ordering on save_object (#1423)

* Fix `Item` field ordering

* Simplify ordering test

.pre-commit-config.yaml

@@ -20,7 +20,7 @@ repos:
 
       - id: ruff-format
         name: ruff-format
-        entry: ruff format --force-exclude --check
+        entry: ruff format --force-exclude
         language: system
         stages: [commit]
         types_or: [python, pyi, jupyter]

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 - Add netCDF to pystac.media_type ([#1386](https://github.com/stac-utils/pystac/pull/1386))
 - Add convenience method for accessing pystac_client ([#1365](https://github.com/stac-utils/pystac/pull/1365))
+- Fix field ordering when saving `Item`s ([#1423](https://github.com/stac-utils/pystac/pull/1423))
 
 ### Changed
 

pystac/item.py

@@ -365,25 +365,25 @@ def to_dict(
         d: dict[str, Any] = {
             "type": "Feature",
             "stac_version": pystac.get_stac_version(),
+            "stac_extensions": self.stac_extensions if self.stac_extensions else [],
             "id": self.id,
-            "properties": self.properties,
             "geometry": self.geometry,
+            "bbox": self.bbox if self.bbox is not None else [],
+            "properties": self.properties,
             "links": [link.to_dict(transform_href=transform_hrefs) for link in links],
             "assets": assets,
         }
 
-        if self.bbox is not None:
-            d["bbox"] = self.bbox
-
-        if self.stac_extensions is not None:
-            d["stac_extensions"] = self.stac_extensions
-
         if self.collection_id:
             d["collection"] = self.collection_id
 
         for key in self.extra_fields:
             d[key] = self.extra_fields[key]
 
+        # This field is prohibited if there's no geometry
+        if not self.geometry:
+            d.pop("bbox")
+
         return d
 
     def clone(self) -> Item:

tests/test_item.py

@@ -108,6 +108,30 @@ def test_asset_absolute_href_no_item_self(self) -> None:
         actual_href = rel_asset.get_absolute_href()
         self.assertEqual(None, actual_href)
 
+    def test_item_field_order(self) -> None:
+        item = pystac.Item.from_file(
+            TestCases.get_path("data-files/item/sample-item.json")
+        )
+        item_dict = item.to_dict(include_self_link=False)
+        expected_order = [
+            "type",
+            "stac_version",
+            "stac_extensions",
+            "id",
+            "geometry",
+            "bbox",
+            "properties",
+            "links",
+            "assets",
+            "collection",
+        ]
+        actual_order = list(item_dict.keys())
+        self.assertEqual(
+            actual_order,
+            expected_order,
+            f"Order was {actual_order}, expected {expected_order}",
+        )
+
     def test_extra_fields(self) -> None:
         item = pystac.Item.from_file(
             TestCases.get_path("data-files/item/sample-item.json")