Add regression test for shell injection fix in GGML conversion (#4773)

AST-based test ensures subprocess.Popen calls in GGML conversion functions
use argv lists instead of shell=True. Companion to PR #4768.

tests/saving/test_save_shell_injection.py

@@ -0,0 +1,74 @@
+from __future__ import annotations
+
+import ast
+from pathlib import Path
+
+
+SAVE_PY = Path(__file__).resolve().parents[2] / "unsloth" / "save.py"
+
+
+def _function_calls(source: str, function_name: str) -> list[ast.Call]:
+    tree = ast.parse(source, filename = str(SAVE_PY))
+    for node in tree.body:
+        if isinstance(node, ast.FunctionDef) and node.name == function_name:
+            return [child for child in ast.walk(node) if isinstance(child, ast.Call)]
+    raise AssertionError(f"Function {function_name} not found in save.py")
+
+
+def _assert_safe_ggml_calls(calls: list[ast.Call]) -> None:
+    popen_calls = []
+    for call in calls:
+        if isinstance(call.func, ast.Attribute) and call.func.attr == "Popen":
+            if (
+                isinstance(call.func.value, ast.Name)
+                and call.func.value.id == "subprocess"
+            ):
+                popen_calls.append(call)
+
+    assert popen_calls, "Expected at least one subprocess.Popen call"
+
+    ggml_calls = []
+    for call in popen_calls:
+        if not call.args:
+            continue
+        argv = call.args[0]
+        if isinstance(argv, ast.List) and len(argv.elts) >= 2:
+            second_arg = argv.elts[1]
+            if (
+                isinstance(second_arg, ast.Constant)
+                and second_arg.value == "llama.cpp/convert-lora-to-ggml.py"
+            ):
+                ggml_calls.append(call)
+
+    assert ggml_calls, "Expected the GGML conversion subprocess call"
+
+    for call in ggml_calls:
+        shell_kwargs = [
+            keyword
+            for keyword in call.keywords
+            if keyword.arg == "shell"
+            and isinstance(keyword.value, ast.Constant)
+            and keyword.value.value is True
+        ]
+        assert not shell_kwargs, "subprocess.Popen must not use shell=True"
+
+        assert call.args, "subprocess.Popen must receive argv as a positional argument"
+        argv = call.args[0]
+        assert isinstance(
+            argv, ast.List
+        ), "subprocess.Popen must be called with an argv list"
+        assert len(argv.elts) == 5, "GGML conversion argv should have five elements"
+
+        second_arg = argv.elts[1]
+        assert isinstance(second_arg, ast.Constant)
+        assert second_arg.value == "llama.cpp/convert-lora-to-ggml.py"
+
+
+def test_ggml_conversion_paths_do_not_use_shell() -> None:
+    source = SAVE_PY.read_text(encoding = "utf-8")
+    for function_name in (
+        "unsloth_convert_lora_to_ggml_and_push_to_hub",
+        "unsloth_convert_lora_to_ggml_and_save_locally",
+    ):
+        calls = _function_calls(source, function_name)
+        _assert_safe_ggml_calls(calls)