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2f0cc99610
https://www.pivotaltracker.com/story/show/113448149 This commit adds a query string to assets URLs which is generated from a hash of the file contents. When asset files are changed they will now be served from a different URL, which means they wont be loaded from browser cache. This is similar to how GOV.UK template adds its version number as a querystring parameter for its assets. This is mostly copied from Digital Marketplace utils: https://github.com/alphagov/digitalmarketplace-utils/pull/102 They have it in a shared codebase, we only have one frontend app so don’t need to do that. Usage in a template: ``` jinja {{ asset_fingerprinter.get_url('stylesheets/application.css') }} ``` Output: ``` static/stylesheets/application.css?418e6f4a6cdf1142e45c072ed3e1c90a ```
47 lines
1.4 KiB
Python
47 lines
1.4 KiB
Python
import hashlib
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import codecs
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class AssetFingerprinter(object):
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"""
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Get a unique hash for an asset file, so that it doesn't stay cached
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when it changes
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Usage:
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in the application
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template_data.asset_fingerprinter = AssetFingerprinter()
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where template data is how you pass variables to every template.
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in template.html:
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{{ asset_fingerprinter.get_url('stylesheets/application.css') }}
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* 'app/static' is assumed to be the root for all asset files
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"""
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def __init__(self, asset_root='/static/', filesystem_path='app/static/'):
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self._cache = {}
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self._asset_root = asset_root
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self._filesystem_path = filesystem_path
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def get_url(self, asset_path):
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if asset_path not in self._cache:
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self._cache[asset_path] = (
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self._asset_root +
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asset_path +
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'?' +
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self.get_asset_fingerprint(self._filesystem_path + asset_path)
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)
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return self._cache[asset_path]
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def get_asset_fingerprint(self, asset_file_path):
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return hashlib.md5(
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self.get_asset_file_contents(asset_file_path).encode('utf-8')
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).hexdigest()
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def get_asset_file_contents(self, asset_file_path):
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with codecs.open(asset_file_path, encoding='utf-8') as asset_file:
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contents = asset_file.read()
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return contents
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