Move default impl to xcm-support. Cooments and fmt

Signed-off-by: Georgi Zlatarev <[email protected]>

traits/src/get_by_key.rs

@@ -1,5 +1,3 @@
-use xcm::v1::MultiLocation;
-
 /// A trait for querying a value by a key.
 pub trait GetByKey<Key, Value> {
 	/// Return the value.
@@ -57,11 +55,3 @@ mod tests {
 		assert_eq!(Test::get(&3), 2);
 	}
 }
-
-// Default implementation for xTokens::MinXcmFee
-pub struct DisabledParachainFee;
-impl GetByKey<MultiLocation, Option<u128>> for DisabledParachainFee {
-    fn get(_key: &MultiLocation) -> Option<u128> {
-        None
-    }
-}

xcm-support/src/lib.rs

@@ -16,7 +16,7 @@ use sp_std::{marker::PhantomData, prelude::*};
 use xcm::latest::prelude::*;
 use xcm_executor::traits::{FilterAssetLocation, MatchesFungible};
 
-use orml_traits::location::Reserve;
+use orml_traits::{location::Reserve, GetByKey};
 
 pub use currency_adapter::{DepositToAlternative, MultiCurrencyAdapter, OnDepositFail};
 
@@ -78,3 +78,11 @@ impl UnknownAsset for () {
 		Err(DispatchError::Other(NO_UNKNOWN_ASSET_IMPL))
 	}
 }
+
+// Default implementation for xTokens::MinXcmFee
+pub struct DisabledParachainFee;
+impl GetByKey<MultiLocation, Option<u128>> for DisabledParachainFee {
+	fn get(_key: &MultiLocation) -> Option<u128> {
+		None
+	}
+}

xtokens/README.md

@@ -61,7 +61,7 @@ parameter_type_with_key! {
 }
 ```
 
-If Parachain don't want have this case, can simply return None:
+If Parachain don't want have this case, can simply return None. A default implementation is provided by `DisabledParachainFee` in `xcm-support`.
 
 ```rust
 parameter_type_with_key! {