Add ConsiderationFromLegacy traits

prdoc/pr_2274.prdoc

@@ -0,0 +1,10 @@
+title: "Add `ConsiderationFromLegacy` traits"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Add a trait that allows to create a `Consideration` from an exact balance deposit. This allows
+      to migrate the legacy currency deposits to the `Consideration` API.
+
+crates:
+  - name: "frame-support"

substrate/frame/support/src/traits/tokens/fungible/mod.rs

@@ -75,6 +75,45 @@ use crate::{
 	traits::{Consideration, Footprint},
 };
 
+/// Extension for the `Consideration` trait to migrate legacy `Currency` deposits.
+///
+/// Provides a `new_from_exact` method for those types using a `fungible` balance frozen,
+/// This method is useful when a new ticket needs to be created with a precise balance, instead of
+/// deriving it from a footprint.
+pub trait FreezeConsiderationFromLegacy<A, F>: Consideration<A>
+where
+	A: 'static,
+	F: 'static + MutateFreeze<A>,
+{
+	/// Create a ticket for a `new` balance attributable to `who`. This ticket *must* ultimately
+	/// be consumed through `update` or `drop` once a footprint changes or is removed.
+	fn new_from_exact(_who: &A, _new: F::Balance) -> Result<Self, DispatchError>
+	where
+		Self: Sized,
+	{
+		Err(DispatchError::Other("Unsupported"))
+	}
+}
+
+/// Extension for `Consideration` trait.
+/// Provides a `new_from_exact` method for those types using a `fungible` balance placed on hold.
+/// This method is useful when a new ticket needs to be created with a precise balance, instead of
+/// deriving it from a footprint.
+pub trait HoldConsiderationFromLegacy<A, F>: Consideration<A>
+where
+	A: 'static,
+	F: 'static + MutateHold<A>,
+{
+	/// Create a ticket for a `new` balance attributable to `who`. This ticket *must* ultimately
+	/// be consumed through `update` or `drop` once a footprint changes or is removed.
+	fn new_from_exact(_who: &A, _new: F::Balance) -> Result<Self, DispatchError>
+	where
+		Self: Sized,
+	{
+		Err(DispatchError::Other("Unsupported"))
+	}
+}
+
 /// Consideration method using a `fungible` balance frozen as the cost exacted for the footprint.
 ///
 /// The aggregate amount frozen under `R::get()` for any account which has multiple tickets,
@@ -120,7 +159,21 @@ impl<
 	}
 }
 
-/// Consideration method using a `fungible` balance frozen as the cost exacted for the footprint.
+impl<
+		A: 'static,
+		F: 'static + MutateFreeze<A>,
+		R: 'static + Get<F::Id>,
+		D: 'static + Convert<Footprint, F::Balance>,
+	> FreezeConsiderationFromLegacy<A, F> for FreezeConsideration<A, F, R, D>
+{
+	fn new_from_exact(who: &A, new: F::Balance) -> Result<Self, DispatchError> {
+		F::increase_frozen(&R::get(), who, new)?;
+		Ok(Self(new, PhantomData))
+	}
+}
+
+/// Consideration method using a `fungible` balance placed on hold as the cost exacted for the
+/// footprint.
 #[derive(
 	CloneNoBound,
 	EqNoBound,
@@ -165,6 +218,19 @@ impl<
 	}
 }
 
+impl<
+		A: 'static,
+		F: 'static + MutateHold<A>,
+		R: 'static + Get<F::Reason>,
+		D: 'static + Convert<Footprint, F::Balance>,
+	> HoldConsiderationFromLegacy<A, F> for HoldConsideration<A, F, R, D>
+{
+	fn new_from_exact(who: &A, new: F::Balance) -> Result<Self, DispatchError> {
+		F::hold(&R::get(), who, new)?;
+		Ok(Self(new, PhantomData))
+	}
+}
+
 /// Basic consideration method using a `fungible` balance frozen as the cost exacted for the
 /// footprint.
 ///
@@ -204,6 +270,19 @@ impl<
 	}
 }
 
+impl<
+		A: 'static,
+		Fx: 'static + MutateFreeze<A>,
+		Rx: 'static + Get<Fx::Id>,
+		D: 'static + Convert<Footprint, Fx::Balance>,
+	> FreezeConsiderationFromLegacy<A, Fx> for LoneFreezeConsideration<A, Fx, Rx, D>
+{
+	fn new_from_exact(who: &A, new: Fx::Balance) -> Result<Self, DispatchError> {
+		ensure!(Fx::balance_frozen(&Rx::get(), who).is_zero(), DispatchError::Unavailable);
+		Fx::set_frozen(&Rx::get(), who, new, Polite).map(|_| Self(PhantomData))
+	}
+}
+
 /// Basic consideration method using a `fungible` balance placed on hold as the cost exacted for the
 /// footprint.
 ///
@@ -245,3 +324,16 @@ impl<
 		let _ = F::burn_all_held(&R::get(), who, BestEffort, Force);
 	}
 }
+
+impl<
+		A: 'static,
+		F: 'static + MutateHold<A>,
+		R: 'static + Get<F::Reason>,
+		D: 'static + Convert<Footprint, F::Balance>,
+	> HoldConsiderationFromLegacy<A, F> for LoneHoldConsideration<A, F, R, D>
+{
+	fn new_from_exact(who: &A, new: F::Balance) -> Result<Self, DispatchError> {
+		ensure!(F::balance_on_hold(&R::get(), who).is_zero(), DispatchError::Unavailable);
+		F::set_on_hold(&R::get(), who, new).map(|_| Self(PhantomData))
+	}
+}