Fix action() callbacks returning -1 corrupting the context

[QuentinRoy]

Summary

action() is supposed to ignore whatever the callback returns and keep the existing context (at least that's what the source tends to indicate, the docs seem outdated, c.f. #266).

There is a particularly edge case where it breaks: if the callback returns -1. The current implementation runs the result through !!~fn(ctx, ev) && ctx, and ~-1 becomes 0, so the reducer returns false instead of the original context.

I assume this somewhat surprising syntax was introduced to save bytes. Unless returning -1 from an action was intended as some kind of escape hatch to clear context, but I cannot think of any use case for it, and it is untested. So I suspect it is a bug. Fortunately, the fix is simple and even shorter (5 chars removed, 3 added, excluding white spaces):

export let action = fn => reduce((ctx, ev) => (fn(ctx, ev), ctx));

This change adds a regression test for that case and replaces the old reducer with the version above so action() always returns the existing context after running the callback.

Testing

• npm test in packages/core
• npm run bundlesize in packages/core

[changeset-bot]

🦋 Changeset detected

Latest commit: 550827e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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robot3	Patch

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[matthewp]

Thanks! I'm AFK for another day, will review tomorrow. Looks good I think though.