[core] fix: toasters closing immediately on hover if timeout is set to 0

[gluxon]

Fixes #6742, which was a regression from #6656 / @blueprintjs/core@5.9.0.

Context

The docs specify that a timeout prop of 0 will cause toasts to persist until a user manually dismisses it.

Milliseconds to wait before automatically dismissing toast. Providing a value less than or equal to 0 will disable the timeout (this is discouraged).

Problem

In a semi-recent refactor of the <OverlayToaster> component, a timeout value of 0 caused the toaster to instead be immediately dismissed. Note how hovering in and out of a progress toast causes it to disappear.

before.mov

Explanation

The new <Toast2> implementation does properly check if the timeout prop is 0 or negative on initial mount.

blueprint/packages/core/src/components/toast/toast2.tsx

Lines 54 to 57 in 488658d

	// start timeout on mount or change, cancel on unmount
	React.useEffect(() => {
	if (timeout != null && timeout > 0) {
	startTimeout();

However, it's incorrect on the pause/resume timeout logic that happens when users mouse over a toaster. This logic always starts a timeout on mouse out, even if the timeout is 0. The original <Toast> implementation didn't do this.

blueprint/packages/core/src/components/toast/toast2.tsx

Lines 87 to 88 in 488658d

	onMouseEnter={clearTimeout}
	onMouseLeave={startTimeout}

Changes

Copying the logic from the original implementation, which doesn't schedule a timeout at all if it's 0.

https://github.com/palantir/blueprint/blob/9dfba77ec5094c7752e5b73eb49a7e72dced9dcb/packages/core/src/components/toast/toast.tsx#L117-LL122

after.mov

[svc-palantir-github]

Fix toasters immediately closing on hover if timeout is set to 0

Build artifact links for this commit: documentation | landing | table | demo

This is an automated comment from the deploy-preview CircleCI job.

[gluxon]

This fix looks simple. The hard part was making sure it was the right fix, which I ended up convincing myself is the case.