Guard precomputed ETag reuse by context - #364
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Validate caller-supplied previous configurations before sending their ETag or reusing them on a 304 response. Environment: Datadog workspace
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| const previousConfiguration = configMatchesContext(options.previousConfiguration, options.context) | ||
| ? options.previousConfiguration | ||
| : undefined |
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major: reusing etag across context must be fine. If context change results in a different response, that response must have a different etag. If context changed in a way that does not affect the response, it should get the same etag (e.g. change in attribute that is not used for evaluation).
So having some etag is better than none. We also want to avoid busting cache on insignificant attribute change.
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Motivation
fetchPrecomputedConfigurationaccepts a caller-supplied previous configuration. When that configuration belongs to context A but the new request targets context B, the public fetcher currently sends context A’s ETag and can reuse A’s assignments after a304 Not Modifiedresponse.This PR is stacked on #351 to demonstrate and close that context-boundary gap.
Changes
previousConfigurationagainst the requested context insidefetchPrecomputedConfigurationIf-None-Matchor handling304304when its ETag is incorrectly sent, while context B returns fresh assignments when it is omittedDecisions
The invariant lives in the exported public fetcher rather than only in
createFlagsConfigurationFetcher, so direct callers receive the same context-safety guarantee as the provider wrapper. Rules configurations remain unchanged because they are not precomputed for an evaluation context.Validation:
yarn workspace @datadog/openfeature-browser test --runInBand test/transport/fetchConfiguration.spec.ts— 25 tests passedyarn workspace @datadog/openfeature-browser typecheckyarn biome check packages/browser/src/transport/fetchConfiguration.ts packages/browser/test/transport/fetchConfiguration.spec.ts --diagnostic-level=error