fix(environment): raise FileNotFoundError instead of silently loading nothing

UnityPy/environment.py

@@ -66,6 +66,11 @@ def __init__(self, *args: FileSourceType, fs: Optional[AbstractFileSystem] = Non
                     elif self.fs.isdir(arg):
                         self.path = arg
                         self.load_folder(arg)
+                    else:
+                        # a path that is neither an existing file nor a directory should fail
+                        # loudly; silently skipping it hides typos behind an empty Environment
+                        if self.load_file(file=arg) is None:
+                            raise FileNotFoundError(f"{arg}: file does not exist")
                 else:
                     self.load_file(file=arg)
 

tests/test_environment.py

@@ -0,0 +1,26 @@
+import pytest
+
+import UnityPy
+
+
+def test_load_missing_file_raises():
+    # silently returning an empty Environment hides typos and wrong paths
+    with pytest.raises(FileNotFoundError):
+        UnityPy.load("definitely_missing_file.unity3d")
+
+
+def test_load_missing_dependency_stays_silent():
+    # missing dependencies (e.g. unshipped externals) are normal and must be skipped
+    env = UnityPy.Environment()
+    assert env.load_file("no_such_dependency.assets", is_dependency=True) is None
+
+
+def test_load_folder_still_works(tmp_path):
+    (tmp_path / "dummy.asset").write_bytes(b"not a real unity file, just needs to exist")
+    env = UnityPy.load(str(tmp_path))
+    assert len(env.files) == 1
+
+
+def test_load_bytes_still_works():
+    env = UnityPy.load(b"UnityFS\x00")
+    assert len(env.files) == 1