Bid 2[diamond] . Generally with a good, distributional hand you should choose to bid your second suit rather than rebid your first suit. You could certainly bid 3[spade] (showing 15+ to 18- HCPs and 6+ spades), but then you have tossed out the opportunity to play hearts or diamonds. 2[diamond] shows 4+ diamonds and 12-17 HCPs.
Let’s look at what might happen over 2[diamond]. If partner bids 3[diamond], you have a fabulous hand that might even make slam in diamonds. If partner bids 2[heart], you can raise to 3[heart] showing a heart fit and 16 to 18 HCPs. If partner preferences back to 2[spade], you can raise to three spades showing 16-18 HCPs and six spades and four diamonds….much more descriptive than jumping to 3[spade] initially.
Yes, Responder can pass 2[diamond], but if they do so, they probably have a singleton spade so you are probably better off in diamonds than spades anyway.
Shape is what can push a hand to games or slams, even when the HCPs are not there. Try to always bid out your shape (your pattern).