Respond to PR comments

pystac/catalog.py

@@ -2,6 +2,7 @@
 
 import os
 from copy import deepcopy
+from functools import partial
 from html import escape
 from typing import (
     TYPE_CHECKING,
@@ -335,7 +336,7 @@ def add_items(
             self.add_item(item, strategy=strategy)
 
     def get_child(
-        self, id: str, recursive: bool = False
+        self, id: str, recursive: bool = False, sort_links_by_id: bool = True
     ) -> Optional[Union["Catalog", Collection]]:
         """Gets the child of this catalog with the given ID, if it exists.
 
@@ -344,20 +345,33 @@ def get_child(
             recursive : If True, search this catalog and all children for the
                 item; otherwise, only search the children of this catalog. Defaults
                 to False.
+            sort_links_by_id : If True, links containing the ID will be checked
+                first. If links doe not contin the ID then setting this to False
+                will improve performance. Defaults to True.
 
         Return:
             Optional Catalog or Collection: The child with the given ID,
             or None if not found.
         """
         if not recursive:
-            return next(
-                (
-                    cast(Union[pystac.Catalog, pystac.Collection], c)
-                    for c in self.get_stac_objects(pystac.RelType.CHILD, _prefer=id)
-                    if c.id == id
-                ),
-                None,
-            )
+            children: Iterable[Union["Catalog", pystac.Collection]]
+            if not sort_links_by_id:
+                children = self.get_children()
+            else:
+
+                def sort_function(id: str, links: List[Link]) -> List[Link]:
+                    return sorted(
+                        links,
+                        key=lambda x: (href := x.get_href()) is None or id not in href,
+                    )
+
+                children = map(
+                    lambda x: cast(Union[pystac.Catalog, pystac.Collection], x),
+                    self.get_stac_objects(
+                        pystac.RelType.CHILD, modify_links=partial(sort_function, id)
+                    ),
+                )
+            return next((c for c in children if c.id == id), None)
         else:
             for root, _, _ in self.walk():
                 child = root.get_child(id, recursive=False)

pystac/stac_object.py

@@ -4,6 +4,7 @@
 from typing import (
     TYPE_CHECKING,
     Any,
+    Callable,
     Dict,
     Iterable,
     List,
@@ -349,7 +350,7 @@ def get_stac_objects(
         self,
         rel: Union[str, pystac.RelType],
         typ: Optional[Type[STACObject]] = None,
-        _prefer: Optional[str] = None,
+        modify_links: Optional[Callable[[List[Link]], List[Link]]] = None,
     ) -> Iterable[STACObject]:
         """Gets the :class:`~pystac.STACObject` instances that are linked to
         by links with their ``rel`` property matching the passed in argument.
@@ -359,20 +360,18 @@ def get_stac_objects(
                 ``rel`` property against.
             typ : If not ``None``, objects will only be yielded if they are instances of
                 ``typ``.
+            modify_links : A function that modifies the list of links before they are
+                iterated over. For instance this option can be used to sort the list
+                so that links matching a particular pattern are earlier in the iterator.
 
         Returns:
             Iterable[STACObjects]: A possibly empty iterable of STACObjects that are
             connected to this object through links with the given ``rel`` and are of
             type ``typ`` (if given).
         """
         links = self.links[:]
-        if _prefer is not None:
-            # if _prefer is set, put links that contain it in their hrefs first
-            links = sorted(
-                links,
-                key=lambda x: (href := x.get_href()) is None
-                or str(_prefer) not in href,
-            )
+        if modify_links:
+            links = modify_links(links)
 
         for i in range(0, len(links)):
             link = links[i]

tests/test_collection.py

@@ -101,9 +101,9 @@ def test_clone_cant_mutate_original(self) -> None:
 
     def test_multiple_extents(self) -> None:
         cat1 = TestCases.case_1()
-        country = cat1.get_child("country-2")
+        country = cat1.get_child("country-1")
         assert country is not None
-        col1 = country.get_child("area-2-2")
+        col1 = country.get_child("area-1-1")
         assert col1 is not None
         col1.validate()
         self.assertIsInstance(col1, Collection)
@@ -541,3 +541,27 @@ def test_remove_hierarchical_links(
     for link in collection.links:
         assert not link.is_hierarchical()
     assert bool(collection.get_single_link("canonical")) == add_canonical
+
+
+@pytest.mark.parametrize("child", ["country-1", "country-2"])
+def test_get_child_checks_links_where_hrefs_contains_id_first(
+    test_case_1_catalog: Catalog, child: str
+) -> None:
+    cat1 = test_case_1_catalog
+    country = cat1.get_child(child)
+    assert country is not None
+    child_links = [link for link in cat1.links if link.rel == pystac.RelType.CHILD]
+    for link in child_links:
+        if country.id not in link.href:
+            assert not link.is_resolved()
+
+
+def test_get_child_sort_links_by_id_is_configurable(
+    test_case_1_catalog: Catalog,
+) -> None:
+    cat1 = test_case_1_catalog
+    country = cat1.get_child("country-2", sort_links_by_id=False)
+    assert country is not None
+    child_links = [link for link in cat1.links if link.rel == pystac.RelType.CHILD]
+    for link in child_links:
+        assert link.is_resolved()