65 lines
1.8 KiB
Python
65 lines
1.8 KiB
Python
from collections import defaultdict
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def patch(key, obj, field, replacement):
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"""Replaces a function in a module or a class.
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Also stores the original function in this module, possible to be retrieved via original(key, obj, field).
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If the function is already replaced by this caller (key), an exception is raised -- use undo() before that.
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Arguments:
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key: identifying information for who is doing the replacement. You can use __name__.
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obj: the module or the class
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field: name of the function as a string
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replacement: the new function
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Returns:
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the original function
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"""
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patch_key = (obj, field)
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if patch_key in originals[key]:
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raise RuntimeError(f"patch for {field} is already applied")
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original_func = getattr(obj, field)
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originals[key][patch_key] = original_func
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setattr(obj, field, replacement)
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return original_func
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def undo(key, obj, field):
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"""Undoes the peplacement by the patch().
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If the function is not replaced, raises an exception.
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Arguments:
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key: identifying information for who is doing the replacement. You can use __name__.
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obj: the module or the class
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field: name of the function as a string
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Returns:
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Always None
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"""
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patch_key = (obj, field)
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if patch_key not in originals[key]:
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raise RuntimeError(f"there is no patch for {field} to undo")
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original_func = originals[key].pop(patch_key)
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setattr(obj, field, original_func)
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return None
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def original(key, obj, field):
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"""Returns the original function for the patch created by the patch() function"""
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patch_key = (obj, field)
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return originals[key].get(patch_key, None)
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originals = defaultdict(dict)
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