fix(site): keep a refusal a browser would not store

[vishr]

What this changes

An explicit Do not allow could be discarded, and analytics could start anyway.

readPreference() fell back to the in-memory answer only when localStorage threw. A browser can let the read succeed and refuse the write: Safari's private mode and an exhausted quota both do. There writePreference kept the choice in memory, setItem threw and was swallowed, and the next readPreference() read null back from storage and returned it.

apply() then treated the reader as unanswered. Neither the denied nor the granted branch ran, so the banner stayed on screen, and in a country the code classifies as not_required the fallback called mayRun("not_required", null), which is true, and loaded the tag.

The stored value still wins when there is one. The change is that the answer given on this page governs it whenever storage has none of its own, however storage failed to keep it.

Why this is correct

• The failure needs getItem to succeed while setItem throws, which is why the original catch-only fallback missed it: nothing throws on the read path.
• memoryPreference is assigned only in writePreference, so falling back to it cannot manufacture a grant the reader never made, and a valid stored value still wins.
• memoryPreference starts null, so a first visit with empty storage still reads as unanswered and the banner still asks.
• Nothing in the site removes the key (no removeItem, no localStorage.clear), so a persisted answer is never revoked out from under an open page.
• The privacy page's control reads through window.oneboxAnalytics.preference, which is readPreference itself, so the banner and the control cannot disagree.
• The cross-tab path already works here: 8146452 applies the preference on the storage event, so a withdrawal in one tab still stops the tag in the others.
• just check passes, including the site build.

Effect on the safety envelope

Makes a refusal effective where it was being dropped. Nothing new is stored, no new request is made, and what is sent when measurement is allowed is unchanged.

fanout carries an identical copy of this component and has the same bug: labstack/fanout#227. It also still needs the cross-tab fix this repository already has.

Checklist

• just check passes locally.
• Tests cover the new behaviour, including the failure paths.
• Generated documentation is current (just check verifies this).
• I have accepted the CLA, or will when the bot asks on my first pull request.

https://claude.ai/code/session_013MqwrF5NA179khDtEQdib5