Avoid calling deepcopy in from_dict methods when unnecessary

pystac/catalog.py

@@ -906,6 +906,7 @@ def from_dict(
         href: Optional[str] = None,
         root: Optional["Catalog"] = None,
         migrate: bool = False,
+        preserve_dict: bool = True,
     ) -> "Catalog":
         if migrate:
             info = identify_stac_object(d)
@@ -916,7 +917,8 @@ def from_dict(
 
         catalog_type = CatalogType.determine_type(d)
 
-        d = deepcopy(d)
+        if preserve_dict:
+            d = deepcopy(d)
 
         id = d.pop("id")
         description = d.pop("description")

pystac/collection.py

@@ -587,6 +587,7 @@ def from_dict(
         href: Optional[str] = None,
         root: Optional[Catalog] = None,
         migrate: bool = False,
+        preserve_dict: bool = True,
     ) -> "Collection":
         if migrate:
             info = identify_stac_object(d)
@@ -597,7 +598,9 @@ def from_dict(
 
         catalog_type = CatalogType.determine_type(d)
 
-        d = deepcopy(d)
+        if preserve_dict:
+            d = deepcopy(d)
+
         id = d.pop("id")
         description = d.pop("description")
         license = d.pop("license")

pystac/item.py

@@ -915,6 +915,7 @@ def from_dict(
         href: Optional[str] = None,
         root: Optional[Catalog] = None,
         migrate: bool = False,
+        preserve_dict: bool = True,
     ) -> "Item":
         if migrate:
             info = identify_stac_object(d)
@@ -925,7 +926,9 @@ def from_dict(
                 f"{d} does not represent a {cls.__name__} instance"
             )
 
-        d = deepcopy(d)
+        if preserve_dict:
+            d = deepcopy(d)
+
         id = d.pop("id")
         geometry = d.pop("geometry")
         properties = d.pop("properties")

pystac/stac_io.py

@@ -99,6 +99,7 @@ def stac_object_from_dict(
         d: Dict[str, Any],
         href: Optional[str] = None,
         root: Optional["Catalog_Type"] = None,
+        preserve_dict: bool = True,
     ) -> "STACObject_Type":
         if identify_stac_object_type(d) == pystac.STACObjectType.ITEM:
             collection_cache = None
@@ -114,15 +115,21 @@ def stac_object_from_dict(
         d = migrate_to_latest(d, info)
 
         if info.object_type == pystac.STACObjectType.CATALOG:
-            result = pystac.Catalog.from_dict(d, href=href, root=root, migrate=False)
+            result = pystac.Catalog.from_dict(
+                d, href=href, root=root, migrate=False, preserve_dict=preserve_dict
+            )
             result._stac_io = self
             return result
 
         if info.object_type == pystac.STACObjectType.COLLECTION:
-            return pystac.Collection.from_dict(d, href=href, root=root, migrate=False)
+            return pystac.Collection.from_dict(
+                d, href=href, root=root, migrate=False, preserve_dict=preserve_dict
+            )
 
         if info.object_type == pystac.STACObjectType.ITEM:
-            return pystac.Item.from_dict(d, href=href, root=root, migrate=False)
+            return pystac.Item.from_dict(
+                d, href=href, root=root, migrate=False, preserve_dict=preserve_dict
+            )
 
         raise ValueError(f"Unknown STAC object type {info.object_type}")
 
@@ -164,7 +171,7 @@ def read_stac_object(
         """
         d = self.read_json(source)
         href = source if isinstance(source, str) else source.get_absolute_href()
-        return self.stac_object_from_dict(d, href=href, root=root)
+        return self.stac_object_from_dict(d, href=href, root=root, preserve_dict=False)
 
     def save_json(
         self, dest: Union[str, "Link_Type"], json_dict: Dict[str, Any]

pystac/stac_object.py

@@ -473,7 +473,7 @@ def from_file(
             href = make_absolute_href(href)
 
         d = stac_io.read_json(href)
-        o = cls.from_dict(d, href=href, migrate=True)
+        o = cls.from_dict(d, href=href, migrate=True, preserve_dict=False)
 
         # Set the self HREF, if it's not already set to something else.
         if o.get_self_href() is None:
@@ -495,6 +495,7 @@ def from_dict(
         href: Optional[str] = None,
         root: Optional["Catalog_Type"] = None,
         migrate: bool = False,
+        preserve_dict: bool = True,
     ) -> "STACObject":
         """Parses this STACObject from the passed in dictionary.
 
@@ -507,6 +508,11 @@ def from_dict(
                 previously resolved instances of the STAC object.
             migrate: Use True if this dict represents JSON from an older STAC object,
                 so that migrations are run against it.
+            preserve_dict: If False, the dict parameter ``d`` may be modified
+                during this method call. Otherwise the dict is not mutated.
+                Defaults to True, which results results in a deepcopy of the
+                parameter. Set to False when possible to avoid the performance
+                hit of a deepcopy. Defaults to True.
 
         Returns:
             STACObject: The STACObject parsed from this dict.

tests/test_catalog.py

@@ -1,3 +1,4 @@
+from copy import deepcopy
 import os
 import json
 import tempfile
@@ -85,6 +86,19 @@ def test_create_and_read(self) -> None:
 
             self.assertEqual(len(list(items)), 8)
 
+    def test_from_dict_preserves_dict(self) -> None:
+        catalog_dict = TestCases.test_case_1().to_dict()
+        param_dict = deepcopy(catalog_dict)
+
+        # test that the parameter is preserved
+        _ = Catalog.from_dict(param_dict)
+        self.assertEqual(param_dict, catalog_dict)
+
+        # assert that the parameter is not preserved with
+        # non-default parameter
+        _ = Catalog.from_dict(param_dict, preserve_dict=False)
+        self.assertNotEqual(param_dict, catalog_dict)
+
     def test_read_remote(self) -> None:
         # TODO: Move this URL to the main stac-spec repo once the example JSON is fixed.
         catalog_url = (

tests/test_collection.py

@@ -1,3 +1,4 @@
+from copy import deepcopy
 import unittest
 import os
 import json
@@ -182,6 +183,21 @@ def test_assets(self) -> None:
         collection = pystac.Collection.from_dict(data)
         collection.validate()
 
+    def test_to_dict_preserves_dict(self) -> None:
+        path = TestCases.get_path("data-files/collections/with-assets.json")
+        with open(path) as f:
+            collection_dict = json.load(f)
+        param_dict = deepcopy(collection_dict)
+
+        # test that the parameter is preserved
+        _ = Collection.from_dict(param_dict)
+        self.assertEqual(param_dict, collection_dict)
+
+        # assert that the parameter is not preserved with
+        # non-default parameter
+        _ = Collection.from_dict(param_dict, preserve_dict=False)
+        self.assertNotEqual(param_dict, collection_dict)
+
     def test_schema_summary(self) -> None:
         collection = pystac.Collection.from_file(
             TestCases.get_path(

tests/test_item.py

@@ -1,3 +1,4 @@
+from copy import deepcopy
 import os
 from datetime import datetime
 import json
@@ -25,9 +26,10 @@ def test_to_from_dict(self) -> None:
         self.maxDiff = None
 
         item_dict = self.get_example_item_dict()
+        param_dict = deepcopy(item_dict)
 
-        assert_to_from_dict(self, Item, item_dict)
-        item = Item.from_dict(item_dict)
+        assert_to_from_dict(self, Item, param_dict)
+        item = Item.from_dict(param_dict)
         self.assertEqual(item.id, "CS3-20160503_132131_05")
 
         # test asset creation additional field(s)
@@ -37,6 +39,14 @@ def test_to_from_dict(self) -> None:
         )
         self.assertEqual(len(item.assets["thumbnail"].properties), 0)
 
+        # test that the parameter is preserved
+        self.assertEqual(param_dict, item_dict)
+
+        # assert that the parameter is not preserved with
+        # non-default parameter
+        _ = Item.from_dict(param_dict, preserve_dict=False)
+        self.assertNotEqual(param_dict, item_dict)
+
     def test_set_self_href_does_not_break_asset_hrefs(self) -> None:
         cat = TestCases.test_case_2()
         for item in cat.get_all_items():