Navigation API: deferred commit (precommit handlers)

Category: Miscellaneous
Type: New or changed feature
Status: In development (Chrome In development)
Intent stage: Start prototyping

Summary

Normally, when navigateEvent.intercept() is called, the intercepted navigation commits (and therefore the URL updates) as soon as the NavigateEvent finishes dispatch. Adding a `precommitHandler` option to navigateEvent.intercept(), similar to `handler`, would defer the commit until that handler (and all other precommit handlers) are resolved, also allowing the handler to change the navigation's URL, info, status, and history handling behavior (push/replace).

Motivation

In developing the navigation API, we heard feedback (https://github.com/WICG/navigation-api/issues/66) that our current policy of immediately committing the navigation does not match with how routing libraries currently model asynchronous same-document navigations.

Standards & signals

Specification: https://github.com/whatwg/html/pull/10919
Firefox: Positive
Safari: Support
Web developers: Strongly positive — Developers are clear that this capability is desired and useful, with the cited issue containing several example use cases. During the Dev Trial we intend to validate that the proposed API shape works well for them.
Tracking bug: https://issues.chromium.org/issues/440190720

Explainers: https://github.com/WICG/navigation-api#precommit-handlers

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