Does damage from a creature with lifelink that is redirected to a planeswalker still grant life?

Lifelink is a static ability that causes life gain whenever the creature deals damage, no matter what it deals damage to. According to CR 702.15b, damage dealt by a source with lifelink causes its controller to gain that much life simultaneously with the damage being dealt.

When a player chooses to redirect combat damage that would be dealt to them so that it instead hits a planeswalker they control (CR 306.7), the source of the damage and its controller do not change — only the recipient does. Because lifelink cares about the source dealing damage, not who receives it, the life gain still happens.

It is important to note that since Magic 2010, lifelink is a static ability, not a triggered ability (CR 702.15a). The life gain happens at the same time as the damage is dealt, not afterward, so there is no window to respond before the life is gained.

Example: Your opponent attacks with a 3/3 creature with lifelink. You block with nothing and choose to redirect the 3 damage to your Planeswalker instead of taking it yourself. Your planeswalker loses 3 loyalty counters, but your opponent still gains 3 life from lifelink — the redirection doesn't change that their creature dealt the damage.

This applies equally to non-combat damage redirected to planeswalkers (e.g., a spell or ability that your opponent redirects). As long as the damaging source has lifelink, its controller gains life equal to the damage dealt.