fix: name a folder or unreadable file in place

A folder or a file the user cannot read at a destination ended --check
and the install on a traceback from the hashing pool. --check now gives
the reason per file, and the install fails that file alone, before any
download for a folder.

install.ps1

@@ -11,7 +11,7 @@
 
     $ErrorActionPreference = "Stop"
     $defaultInstallUrl = "https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-    $defaultInstallSha256 = "6d8af0dbca6697ba71692e5e482c8a16d9e8b9896652fec722d9c84f23bba047"
+    $defaultInstallSha256 = "c361b511d9550b2115d918a0233115cd9f42920bce881f41395c3d7614be534d"
     $maximumInstallerBytes = 2MB
     $installerExit = 0
     $installer = if ($PSScriptRoot) { Join-Path $PSScriptRoot "install.py" } else { $null }

install.py

@@ -4046,9 +4046,18 @@ def _classify_local(entry: dict, dest: Path) -> str:
         for name in ("sha256", "sha1")
         if entry.get(name)
     }
+    if not dest.is_file():
+        # A folder at the file's place: --check says so, an install fails
+        # on that file alone.
+        return "mismatched"
     if not expected:
         return "up_to_date"
-    actual = _digest_file(dest, tuple(expected))
+    try:
+        actual = _digest_file(dest, tuple(expected))
+    except OSError:
+        # Unreadable (no permission, a read error on a failing card): its
+        # contents are not known to be the right ones.
+        return "mismatched"
     if all(actual[name] == value for name, value in expected.items()):
         return "up_to_date"
     return "mismatched"
@@ -4444,6 +4453,9 @@ def _download_one(
         if _write_refused(exc):
             return f["dest"], False, NOT_WRITABLE
         return f["dest"], False, exc.strerror or str(exc)
+    if dest.is_dir():
+        # Fetched, it failed only at the rename, on an errno and two paths.
+        return f["dest"], False, FOLDER_IN_PLACE
 
     if copy is not None:
         result = _copy_local(f, bios_path, dest, copy, progress)
@@ -4834,6 +4846,7 @@ READ_ONLY = "file in place is read-only"
 # A file in place whose content differs, which could not be moved aside: it
 # is left as it is rather than lost.
 NOT_KEPT = "file in place could not be kept aside"
+FOLDER_IN_PLACE = "a folder sits where this file goes: move it away, then run again"
 
 
 def _clear_read_only(dest: Path) -> None:
@@ -7539,12 +7552,14 @@ def _wrong_contents(
     owners: dict[str, list[dict]] | None = None,
 ) -> str:
     """Why the file at an entry's place is not the one the list installs."""
+    if path.is_dir():
+        return FOLDER_IN_PLACE
     try:
         size = path.stat().st_size
         with open(path, "rb") as handle:
             head = handle.read(4)
-    except OSError:
-        return ""
+    except OSError as exc:
+        return f"could not be read ({exc.strerror or exc}): its contents are unknown"
     sha1 = index.sha1(path)
     owner = _content_owner(sha1, entry, files, owners)
     if owner:

install.sh

@@ -18,7 +18,7 @@ esac
 TEMP_INSTALLER=""
 TEMP_DIRECTORY=""
 DEFAULT_INSTALL_URL="https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-DEFAULT_INSTALL_SHA256="6d8af0dbca6697ba71692e5e482c8a16d9e8b9896652fec722d9c84f23bba047"
+DEFAULT_INSTALL_SHA256="c361b511d9550b2115d918a0233115cd9f42920bce881f41395c3d7614be534d"
 MAX_INSTALLER_BYTES=2097152
 
 cleanup() {

tests/test_install_selection.py

@@ -1501,5 +1501,38 @@ class TheTitleASetupPrints(unittest.TestCase):
         self.assertEqual(install.system_aliases(manifest)["Sony PlayStation"], "arcade")
 
 
+class SomethingElseAtADestination(unittest.TestCase):
+    """A folder, or a file this user cannot read, at a destination ended
+    --check and the install on an IsADirectoryError traceback."""
+
+    def prepare(self, repo: FakeRepository) -> None:
+        (repo.dest / "scph5500.bin").mkdir(parents=True)
+        unreadable = repo.dest / "scph5501.bin"
+        unreadable.write_bytes(b"x")
+        unreadable.chmod(0)
+
+    @unittest.skipIf(os.name == "nt" or (hasattr(os, "geteuid") and os.geteuid() == 0),
+                     "a mode of 0 stops no read on Windows or as root")
+    def test_each_says_why_in_the_check_and_the_install(self):
+        with FakeRepository() as repo:
+            self.prepare(repo)
+            proc = repo.run("--check")
+            self.assertEqual(proc.returncode, 1, proc.stderr)
+            self.assertNotIn("Traceback", proc.stderr)
+            self.assertIn("    wrong hash: scph5500.bin\n      a folder sits where this "
+                          "file goes: move it away, then run again", proc.stdout)
+            self.assertIn("    wrong hash: scph5501.bin\n      could not be read "
+                          "(Permission denied)", proc.stdout)
+            proc = repo.run("--yes")
+            self.assertEqual(proc.returncode, 1, proc.stderr)
+            self.assertNotIn("Traceback", proc.stderr)
+            self.assertIn("failed: scph5500.bin (a folder sits where this file goes",
+                          proc.stdout)
+            self.assertIn("failed: scph5501.bin (file in place could not be kept aside",
+                          proc.stdout)
+            self.assertTrue((repo.dest / "scph5500.bin").is_dir())
+            self.assertIn("gba_bios.bin", repo.installed())
+
+
 if __name__ == "__main__":
     unittest.main()