Updates to TargetFile.get_prefixed_paths()

* Use the same solution for producing the paths as we already do in ngclient
* Fix linting issues
* Modify the test results according to new code (I believe these are
  correct, although some cases are so edge cases that disagreement may
  exist. Most importantly I think the method should always return as
  many paths as there are hashes listed

Signed-off-by: Jussi Kukkonen <jkukkonen@google.com>

Author: jku

tests/test_api.py

@@ -725,41 +725,33 @@ def test_targetfile_from_data(self) -> None:
         targetfile_from_data = TargetFile.from_data(target_file_path, data)
         targetfile_from_data.verify_length_and_hashes(data)
 
-    def test_targetfile_hash_prefix_paths(self) -> None:
-        target = TargetFile(
-            100, {"sha256": "abc", "md5": "def"}, "public/path/file.ext"
+    def test_targetfile_get_prefixed_paths(self) -> None:
+        target = TargetFile(100, {"sha256": "abc", "md5": "def"}, "a/b/f.ext")
+        self.assertEqual(
+            target.get_prefixed_paths(), ["a/b/abc.f.ext", "a/b/def.f.ext"]
         )
-        self.assertEqual(sorted(target.get_prefixed_paths()), ["public/path/abc.file.ext", "public/path/def.file.ext"])
 
-        target = TargetFile(
-            100, {"sha256": "abc", "md5": "def"}, ""
-        )
-        self.assertEqual(sorted(target.get_prefixed_paths()), [])
+        target = TargetFile(100, {"sha256": "abc", "md5": "def"}, "")
+        self.assertEqual(target.get_prefixed_paths(), ["abc.", "def."])
 
-        target = TargetFile(
-            100, {"sha256": "abc", "md5": "def"}, "public/path/"
-        )
-        self.assertEqual(sorted(target.get_prefixed_paths()), [])
+        target = TargetFile(100, {"sha256": "abc", "md5": "def"}, "a/b/")
+        self.assertEqual(target.get_prefixed_paths(), ["a/b/abc.", "a/b/def."])
 
-        target = TargetFile(
-            100, {"sha256": "abc", "md5": "def"}, "file.ext"
+        target = TargetFile(100, {"sha256": "abc", "md5": "def"}, "f.ext")
+        self.assertEqual(
+            target.get_prefixed_paths(), ["abc.f.ext", "def.f.ext"]
         )
-        self.assertEqual(sorted(target.get_prefixed_paths()), ["abc.file.ext", "def.file.ext"])
 
-        target = TargetFile(
-            100, {"sha256": "abc", "md5": "def"}, "public/path/.ext"
+        target = TargetFile(100, {"sha256": "abc", "md5": "def"}, "a/b/.ext")
+        self.assertEqual(
+            target.get_prefixed_paths(), ["a/b/abc..ext", "a/b/def..ext"]
         )
-        self.assertEqual(sorted(target.get_prefixed_paths()), ["public/path/abc..ext", "public/path/def..ext"])
 
-        target = TargetFile(
-            100, {"sha256": "abc"}, "/root/file.ext"
-        )
-        self.assertEqual(sorted(target.get_prefixed_paths()), ["/root/abc.file.ext"])
+        target = TargetFile(100, {"sha256": "abc"}, "/root/file.ext")
+        self.assertEqual(target.get_prefixed_paths(), ["/root/abc.file.ext"])
 
-        target = TargetFile(
-            100, {"sha256": "abc"}, "/"
-        )
-        self.assertEqual(sorted(target.get_prefixed_paths()), [])
+        target = TargetFile(100, {"sha256": "abc"}, "/")
+        self.assertEqual(target.get_prefixed_paths(), ["/abc."])
 
     def test_is_delegated_role(self) -> None:
         # test path matches

tuf/api/metadata.py

@@ -33,7 +33,6 @@
 import io
 import logging
 import tempfile
-import pathlib
 from datetime import datetime
 from typing import (
     IO,
@@ -1740,28 +1739,13 @@ def verify_length_and_hashes(self, data: Union[bytes, IO[bytes]]) -> None:
 
     def get_prefixed_paths(self) -> List[str]:
         """
-        Returns hash-prefixed paths for the given target file path. Empty result in the case of an invalid path.
-
-        Expects self.path to be a URL path fragment, not a filesystem path.
+        Return hash-prefixed URL path fragments for the target file path.
         """
         paths = []
-        try:
-            if not self.path:
-                raise ValueError
-            elif "/" not in self.path:
-                parent, name = None, self.path
-            else:
-                parent, name = self.path.rsplit("/", 1)
-                if name == "": 
-                    raise ValueError
-        except ValueError:
-            return paths
+        parent, sep, name = self.path.rpartition("/")
+        for hash_value in self.hashes.values():
+            paths.append(f"{parent}{sep}{hash_value}.{name}")
 
-        for hash in self.hashes.values():
-            path = f"{hash}.{name}"
-            if parent is not None:
-                path = f"{parent}/{path}"
-            paths.append(path)
         return paths