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Utils: add strict mode to load_file #13265

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Merged
merged 3 commits into from
Oct 16, 2025
Merged

Utils: add strict mode to load_file #13265

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a15dfa0
Add backwards-compatible strict mode to load_file
simonrw Oct 14, 2025
992867b
Load file strictly in deploy_cfn_template
simonrw Oct 14, 2025
5129ea4
Add typing and docstring
simonrw Oct 16, 2025
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2 changes: 1 addition & 1 deletion localstack-core/localstack/testing/aws/cloudformation_utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,7 @@ def load_template_file(file_path: str | os.PathLike, *, path_ctx: str | os.PathL
elif not file_path_obj.is_absolute():
raise ValueError("Provided path must be absolute if no path_ctx is provided")

return load_file(file_path_obj.absolute())
return load_file(file_path_obj.absolute(), strict=True)


# TODO: TBH this utility really doesn't add anything, probably better to just remove it
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21 changes: 19 additions & 2 deletions localstack-core/localstack/utils/files.py
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Expand Up @@ -80,9 +80,26 @@ def _opener(path, flags):
f.flush()


def load_file(file_path: str, default=None, mode=None):
def load_file(
file_path: str | os.PathLike,
default: str | bytes | None = None,
mode: str | None = None,
strict: bool = False,
) -> str | bytes | None:
"""
Return file contents

:param file_path: path of the file
:param default: if strict=False then return this value if the file does not exist
:param mode: mode to open the file with (e.g. `r`, `rw`)
:param strict: raise an error if the file path is not a file
:return: the file contents
"""
if not os.path.isfile(file_path):
return default
if strict:
raise FileNotFoundError(file_path)
else:
return default
if not mode:
mode = "r"
with open(file_path, mode) as f:
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9 changes: 9 additions & 0 deletions tests/unit/test_common.py
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Expand Up @@ -546,6 +546,15 @@ def test_save_load_file(tmp_path):
assert content + more_content == load_file(file_name)


def test_load_file_strict(tmp_path):
file_name = tmp_path / short_uid()
assert not os.path.isfile(file_name)

assert load_file(file_name) is None
with pytest.raises(FileNotFoundError):
load_file(file_name, strict=True)


def test_save_load_file_with_permissions(tmp_path):
file_name = tmp_path / (f"special_permissions_{short_uid()}")
content = f"some_content_{short_uid()}"
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