ONNX importer fails when `--temp-dir` is set and `--data-dir` is not

[tkocmathla]

In the Python-based ONNX importer, if --temp-dir is specified and --data-dir is not, and the model large enough to fail in-memory shape inference, the import fails with this error:

Traceback (most recent call last):
<internal traces elided>
  File "<elided>/import_onnx/__main__.py", line 38, in main
    model_proto = load_onnx_model(args)
                  ^^^^^^^^^^^^^^^^^^^^^
  File "<elided>/import_onnx/__main__.py", line 139, in load_onnx_model
    data_dir = Path(input_dir if args.temp_dir is None else args.data_dir)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<elided>/python3.11/pathlib.py", line 871, in __new__
    self = cls._from_parts(args)
           ^^^^^^^^^^^^^^^^^^^^^
  File "<elided>/python3.11/pathlib.py", line 509, in _from_parts
    drv, root, parts = self._parse_args(args)
                       ^^^^^^^^^^^^^^^^^^^^^^
  File "<elided>/python3.11/pathlib.py", line 493, in _parse_args
    a = os.fspath(a)
        ^^^^^^^^^^^^
TypeError: expected str, bytes or os.PathLike object, not NoneType

I think the issue is this line that tries to set up data_dir based on whether --data-dir is set, but it mistakenly checks args.temp_dir instead:

torch-mlir/python/torch_mlir/tools/import_onnx/__main__.py

Line 149 in 716303a

data_dir = Path(input_dir if args.temp_dir is None else args.data_dir)

I changed that line with this patch and it seems to be working for me now:

diff --git c/python/torch_mlir/tools/import_onnx/__main__.py i/python/torch_mlir/tools/import_onnx/__main__.py
index 4f852d34..ff4f651e 100644
--- c/python/torch_mlir/tools/import_onnx/__main__.py
+++ i/python/torch_mlir/tools/import_onnx/__main__.py
@@ -136,7 +136,7 @@ def load_onnx_model(args: argparse.Namespace) -> onnx.ModelProto:

     # Load the temp file and the external data.
     inferred_model = onnx.load(temp_inferred_file, load_external_data=False)
-    data_dir = Path(input_dir if args.temp_dir is None else args.data_dir)
+    data_dir = Path(input_dir if args.data_dir is None else args.data_dir)
     onnx.load_external_data_for_model(inferred_model, str(data_dir))

     # Remove the inferred shape file unless asked to keep it