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from ..utils import get_singleton
class JustInTime:
"""
A strategy that ensures the file exists right before it's needed.
"""
def on_existence_required(self, file):
file.generate()
def on_content_required(self, file):
file.generate()
class Optimistic:
"""
A strategy that acts immediately when the source file changes and assumes
that the cache files will not be removed (i.e. it doesn't ensure the
cache file exists when it's accessed).
"""
def on_source_saved(self, file):
file.generate()
def should_verify_existence(self, file):
return False
class DictStrategy:
def __init__(self, callbacks):
for k, v in callbacks.items():
setattr(self, k, v)
def load_strategy(strategy):
if isinstance(strategy, str):
strategy = get_singleton(strategy, 'cache file strategy')
elif isinstance(strategy, dict):
strategy = DictStrategy(strategy)
elif callable(strategy):
strategy = strategy()
return strategy
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