[ankitdhandharia]

Issue #, if available: Fixes #5033

Description of changes:

With ModelTrainer(training_mode=Mode.LOCAL_CONTAINER), an S3 input channel that points to a single object (for example s3://bucket/train.csv) fails before the container starts:

FileNotFoundError: [Errno 2] No such file or directory: '<local_container_root>/tmpXXXX/train.csv'

_LocalContainer._get_data_source_local_path picks the download directory with TemporaryDirectory(prefix=...).name. Nothing holds on to the TemporaryDirectory object, so it is finalized right away and deletes the directory. Only the path string is kept. Prefix inputs still work because _download_files_under_prefix runs os.makedirs for every object. The single-object branch of download_folder writes straight into target, which no longer exists.

Changes:

• _get_data_source_local_path in both sagemaker-train (sagemaker/train/local/local_container.py) and sagemaker-core (sagemaker/core/modules/local_core/local_container.py) now creates a real directory with tempfile.mkdtemp(dir=container_root). The directory is still recorded in _temporary_folders, and train() already removes those with _rmtree when the job finishes.
• download_folder creates target before downloading a single object, so the single-file branch matches the prefix branch for any caller.

Testing done:

• Regression testing before fix:
  • cd sagemaker-core && python -m pytest tests/unit/modules/local_core/test_local_container.py: test_get_data_source_local_path_s3_single_file_dir_exists failed with AssertionError: Target directory does not exist (2 failed, 39 passed).
  • cd sagemaker-core && python -m pytest tests/unit/test_common_utils.py -k 'DownloadFolder or download_folder': test_download_folder_single_file_creates_missing_target failed with FileNotFoundError: [Errno 2] No such file or directory (1 failed, 3 passed).
  • cd sagemaker-train && python -m pytest tests/unit/train/local/test_local_container.py: test_get_data_source_local_path_s3_single_file_dir_exists failed with AssertionError: Target directory does not exist (1 failed, 13 passed).
• Unit tests after fix:
  • cd sagemaker-core && python -m pytest tests/unit/modules/local_core/test_local_container.py -q -p no:cacheprovider: 41 passed
  • cd sagemaker-core && python -m pytest tests/unit/test_common_utils.py -q -k 'DownloadFolder or download_folder': 4 passed (259 deselected)
  • cd sagemaker-core && python -m pytest tests/unit/test_common_utils.py -q: 263 passed
  • cd sagemaker-train && python -m pytest tests/unit/train/local/test_local_container.py -q: 14 passed
  • cd sagemaker-train && python -m pytest tests/unit/train/test_model_trainer.py -q -k 'local': 3 passed (85 deselected)
  • cd sagemaker-core && python -m pytest tests/unit/local/ -q: 176 passed
  • cd sagemaker-train && python -m pytest tests/unit/train/local/test_data.py tests/unit/train/local/test_entities.py -q: 43 passed (6 skipped)
• Lint and format checks:
  • black --check -l 100 passed on all modified files
  • flake8 passed with 0 errors on all modified files

Merge Checklist

General

• I have read the CONTRIBUTING doc
• I used the commit message format described in CONTRIBUTING

Tests

• I have added tests that prove my fix is effective
• Unit tests pass locally with my changes

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