Implement deterministic GeoDataset (#1908)

tests/datasets/test_geo.py

@@ -171,6 +171,21 @@ def test_files_property_for_virtual_files(self) -> None:
         ]
         assert len(CustomGeoDataset(paths=paths).files) == len(paths)
 
+    def test_files_property_ordered(self) -> None:
+        """Ensure that the list of files is ordered."""
+        paths = ["file://file3.tif", "file://file1.tif", "file://file2.tif"]
+        assert CustomGeoDataset(paths=paths).files == sorted(paths)
+
+    def test_files_property_deterministic(self) -> None:
+        """Ensure that the list of files is consistent regardless of their original
+        order.
+        """
+        paths1 = ["file://file3.tif", "file://file1.tif", "file://file2.tif"]
+        paths2 = ["file://file2.tif", "file://file3.tif", "file://file1.tif"]
+        assert (
+            CustomGeoDataset(paths=paths1).files == CustomGeoDataset(paths=paths2).files
+        )
+
 
 class TestRasterDataset:
     @pytest.fixture(params=zip([["R", "G", "B"], None], [True, False]))

torchgeo/datasets/geo.py

@@ -285,7 +285,7 @@ def res(self, new_res: float) -> None:
         self._res = new_res
 
     @property
-    def files(self) -> set[str]:
+    def files(self) -> list[str]:
         """A list of all files in the dataset.
 
         Returns:
@@ -314,7 +314,8 @@ def files(self) -> set[str]:
                     UserWarning,
                 )
 
-        return files
+        # Sort the output to enforce deterministic behavior.
+        return sorted(files)
 
 
 class RasterDataset(GeoDataset):