fix caching issue.

With the same scan_file the loader due to caching gave back a mutable ScanImage. Moved caching to only the load Surface from scan-file, but makes every load a new ScanImage object.

Author: Raytesnel

packages/scratch-core/src/parsers/loaders.py

@@ -22,6 +22,14 @@
 
 
 @lru_cache(maxsize=1)
+def _load_surface(scan_file: Path) -> Surface:
+    """Cache the scan file to a Surface
+    :param scan_file: The path to the file containing the scanned image data.
+    :returns: An instance of `Surface`.
+    """
+    return Surface.load(scan_file)
+
+
 @log_railway_function(
     "Failed to load image file",
     "Successfully loaded scan file",
@@ -33,7 +41,7 @@ def load_scan_image(scan_file: Path) -> ScanImage:
     :param scan_file: The path to the file containing the scanned image data.
     :returns: An instance of `ScanImage`.
     """
-    surface = Surface.load(scan_file)
+    surface = _load_surface(scan_file)
     data = np.asarray(surface.data, dtype=np.float64) * micro
     step_x = surface.step_x * micro
     step_y = surface.step_y * micro

packages/scratch-core/tests/parsers/test_loaders.py

@@ -10,7 +10,7 @@
 
 from container_models.scan_image import ScanImage
 from parsers import load_scan_image, subsample_scan_image
-from parsers.loaders import make_isotropic
+from parsers.loaders import make_isotropic, _load_surface
 
 from ..helper_function import unwrap_result
 
@@ -54,7 +54,7 @@ class FakeSurfaceTwo:
 
     @pytest.fixture(autouse=True)
     def empty_cache_for_test(self):
-        load_scan_image.cache_clear()
+        _load_surface.cache_clear()
         yield
 
     def test_load_scan_image_is_cached(self, tmp_path: Path) -> None:
@@ -91,7 +91,7 @@ def test_load_scan_image_only_caches_one_image(self, tmp_path: Path) -> None:
             _image_3 = load_scan_image(scan_file_2)
 
         # Assert
-        info = load_scan_image.cache_info()
+        info = _load_surface.cache_info()
         assert info.hits == 1, "one cache hit expected"
         assert info.misses == 2, "two different files loaded"
         assert info.currsize == 1, "Cache should only hold one item"