Swap route via WETH

[romanbsd]

The make_trade (as well as get price methods) have a route of [token1, WETH, token2]
https://github.com/uniswap-python/uniswap-python/blob/master/uniswap/uniswap.py#L686

Does it mean that the swaps incur 0.6% fee?

[liquid-8]

The make_trade (as well as get price methods) have a route of [token1, WETH, token2]

By default. You can specify the route parameter (for univ2 at least). Mentioned route causes two swaps: token1->weth; weth->token2. Taker's fee is applied twice, so total fee = 1-0.997^2=0.005991

[romanbsd]

I don't think you can do that using this library.

[liquid-8]

I've checked this. Well, it is possible for get_price methods, but make_swap methods don't have such an option actually, which is surprising. However, it is relatively easy to add it.

[romanbsd]

When I come to think about it, the default should be [t0,t1] (and a boolean for going through [t0,weth,t1] route) and in case such pair doesn't exist an exception thrown suggesting to set the boolean parameter to true. Because incurring double fee breaks the principle of least surprise.

[ErikBjare]

Well, it is possible for get_price methods, but make_swap methods don't have such an option actually, which is surprising. However, it is relatively easy to add it.

@liquid-8 Yeah, I might look into that.

When I come to think about it, the default should be [t0,t1] (and a boolean for going through [t0,weth,t1] route) and in case such pair doesn't exist an exception thrown suggesting to set the boolean parameter to true.

@romanbsd The issue is that [t0, t1] is often a much less liquid pair than [t0, weth, t1], so chances are high that such a trade might have significant price impact and therefore a bad execution price.

Swaps are actually made using [t0, t1] right now though (no multi-hop swaps yet), so yeah...

Because incurring double fee breaks the principle of least surprise.

I agree, but in this case ensuring that the pair assumed has liquidity takes precedence imo (I'd be more surprised if I made a terrible trade, as in #198, then if I incurred an additional 0.3% fee).

[ErikBjare]

@liquid-8 Apparently I had already been working on that in #221, feel free to continue the work! (I might not have time)

[romanbsd]

Insufficient liquidity is caveat emptor. But maybe some safeguard is needed indeed...

[starascendin]

Hey all, so i've been running into this issue because sometimes my clients have LP as [t0, stablecoin] instead of [t0, bnb/eth/base_token], and not being able to customize route in make_trade is not ideal.

Should we add an optional param route= to make_trade? I have a working solution; i'd be happy to contribute