Close label files reliably after reads and writes

anylabeling/views/labeling/label_file.py

@@ -17,7 +17,8 @@
 def io_open(name, mode):
     assert mode in ["r", "w"]
     encoding = "utf-8"
-    yield open(name, mode, encoding=encoding)
+    with open(name, mode, encoding=encoding) as file:
+        yield file
 
 
 class LabelFileError(Exception):

tests/test_label_file.py

@@ -0,0 +1,50 @@
+"""Tests for reliable label-file reads and overwrites."""
+
+import io
+import os
+import tempfile
+import unittest
+
+from PIL import Image
+
+from anylabeling.views.labeling.label_file import LabelFile, io_open
+
+
+class TestLabelFileIO(unittest.TestCase):
+    def test_io_open_closes_file_after_context(self):
+        with tempfile.TemporaryDirectory() as directory:
+            filename = os.path.join(directory, "labels.json")
+
+            with io_open(filename, "w") as file:
+                file.write("{}")
+                opened_file = file
+
+            self.assertTrue(opened_file.closed)
+
+    def test_existing_label_file_can_be_overwritten_and_removed(self):
+        image_buffer = io.BytesIO()
+        Image.new("RGB", (2, 2)).save(image_buffer, format="PNG")
+
+        with tempfile.TemporaryDirectory() as directory:
+            filename = os.path.join(directory, "labels.json")
+            label_file = LabelFile()
+            for revision in (1, 2):
+                label_file.save(
+                    filename=filename,
+                    shapes=[],
+                    image_path="image.png",
+                    image_height=2,
+                    image_width=2,
+                    image_data=image_buffer.getvalue(),
+                    other_data={"revision": revision},
+                )
+
+            loaded = LabelFile(filename)
+            self.assertEqual(loaded.other_data["revision"], 2)
+
+            os.remove(filename)
+            self.assertFalse(os.path.exists(filename))
+
+
+if __name__ == "__main__":
+    unittest.main()