Created
August 13, 2024 12:09
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Protect parts of your code with a contract. Contract-protected code can't be (accidentally) changed.
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| import inspect | |
| import ast | |
| import hashlib | |
| import sys | |
| import textwrap | |
| from contextlib import contextmanager | |
| def indent(line): | |
| return len(line) - len(line.lstrip(" ")) | |
| @contextmanager | |
| def contract(description, *, signature=None): | |
| f = sys._getframe(2) | |
| lines = inspect.getsource(f).split("\n") | |
| start = f.f_lineno | |
| start_indent = indent(lines[start]) | |
| stop = next( | |
| i for i in range(start + 1, len(lines)) if indent(lines[i]) < start_indent | |
| ) | |
| content = textwrap.dedent("\n".join(lines[start:stop])) | |
| hash_ = hashlib.sha1(ast.unparse(ast.parse(content)).encode("utf-8")).hexdigest()[:8] | |
| if signature is None: | |
| raise ValueError(f"No signature passed, should be: {hash_}") | |
| if signature != hash_: | |
| raise RuntimeError(f"Contract-protected code was modified. The following contract needs to be fulfilled by the code:\n\n{description}\n\nRevert your changes or adjust the signature (by leaving it empty for one run), if you have documented your change.") | |
| yield | |
| if __name__ == "__main__": | |
| with contract("Prints hello and bye", signature="faa7b015"): | |
| print("hello") | |
| if True: | |
| print("bye") |
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