accept-encoding.acceptable_offers is not very useful for the common use case

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#387 4 comments 2 reactions 0 assignees View on GitHub

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
api, backend

Research direction

Start by locating the implementations of acceptable_offers and the deprecated best_match API in the WebOb source, then inspect their tests. Compare behavior for a missing Accept-Encoding header with the examples in this issue; done means the proposed API handles the default identity encoding and preserves offer ordering without the old quality multiplier logic.

Written by the indexing model from the issue text.

Description

While this api is compliant with the RFC at https://tools.ietf.org/html/rfc7231#section-5.3.4, it is not what anybody really expects or wants in the case of a missing header. The answer is pretty much always to use identity when a header is missing. This is what the deprecated best_match api used to do, with best_match(['identity', 'gzip'], default_match='identity').

>>> create_accept_encoding_header(None).acceptable_offers(['identity', 'gzip'])
[('identity', 1.0), ('gzip', 1.0)]

>>> create_accept_encoding_header(None).best_match(['identity', 'gzip'], default_match='identity')
'identity'

The proposed api would be something that implements the following:

offers = ['gzip', 'identity']  # order matters here
default_encoding = 'identity'
if request.accept_encoding:
    encodings = request.accept_encoding.acceptable_offers(offers)
    target_encoding = encodings[0][0] if encodings else default_encoding
else:
    target_encoding = default_encoding

This is very similar to best_match but without any weird server-side quality multiplier logic.

Dominant language
Python
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Forks
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