Test that file order is irrelevant for DirFingerprints

src/fscacher/cache.py

@@ -197,17 +197,17 @@ def to_tuple(self):
 class DirFingerprint:
     def __init__(self):
         self.last_modified = None
-        self.hash_ords = None
+        self.hash = None
 
     def add_file(self, path, fprint: FileFingerprint):
         fprint_hash = md5(
             ascii((str(path), fprint.to_tuple())).encode("us-ascii")
         ).digest()
-        if self.hash_ords is None:
-            self.hash_ords = fprint_hash
+        if self.hash is None:
+            self.hash = fprint_hash
             self.last_modified = fprint.mtime_ns
         else:
-            self.hash_ords = xor_bytes(self.hash_ords, fprint_hash)
+            self.hash = xor_bytes(self.hash, fprint_hash)
             if self.last_modified < fprint.mtime_ns:
                 self.last_modified = fprint.mtime_ns
 
@@ -218,10 +218,10 @@ def modified_in_window(self, min_dtime):
             return abs(time.time() - self.last_modified * 1e-9) < min_dtime
 
     def to_tuple(self):
-        if self.hash_ords is None:
+        if self.hash is None:
             return (None,)
         else:
-            return (bytes(self.hash_ords).hex(),)
+            return (self.hash.hex(),)
 
 
 def xor_bytes(b1: bytes, b2: bytes) -> bytes:

src/fscacher/tests/test_cache.py

@@ -8,6 +8,7 @@
 import time
 import pytest
 from .. import PersistentCache
+from ..cache import DirFingerprint, FileFingerprint
 
 platform_system = platform.system().lower()
 on_windows = platform_system == "windows"
@@ -415,3 +416,29 @@ def memoread(filepath, arg, kwarg=None):
     assert len(calls) == ncalls + 1
     assert memoread(arg=1, filepath=path) == "content"
     assert len(calls) == ncalls + 1
+
+
+def test_dir_fingerprint_order_irrelevant(tmp_path):
+    start = time.time()
+    file1 = tmp_path / "apple.txt"
+    file1.write_text("Apple\n")
+    os.utime(file1, (start - 1, start - 1))
+    file2 = tmp_path / "banana.txt"
+    file2.write_text("This is test text.\n")
+    os.utime(file2, (start - 2, start - 2))
+    file3 = tmp_path / "coconut.txt"
+    file3.write_text("Lorem ipsum dolor sit amet, consectetur adipisicing elit\n")
+    os.utime(file3, (start - 3, start - 3))
+    df_tuples = []
+    for file_list in [
+        [file1, file2, file3],
+        [file3, file2, file1],
+        [file2, file1, file3],
+    ]:
+        dprint = DirFingerprint()
+        for f in file_list:
+            fprint = FileFingerprint.from_stat(os.stat(f))
+            dprint.add_file(f, fprint)
+        df_tuples.append(dprint.to_tuple())
+    for i in range(1, len(df_tuples)):
+        assert df_tuples[0] == df_tuples[i]