Allow the treasury to have a maximum bound on the bond (#10689)

* Allow the treasury to have a maximum bound on the bond

* Update frame/treasury/src/lib.rs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

substrate/frame/treasury/src/lib.rs

@@ -168,6 +168,10 @@ pub mod pallet {
 		#[pallet::constant]
 		type ProposalBondMinimum: Get<BalanceOf<Self, I>>;
 
+		/// Maximum amount of funds that should be placed in a deposit for making a proposal.
+		#[pallet::constant]
+		type ProposalBondMaximum: Get<Option<BalanceOf<Self, I>>>;
+
 		/// Period between successive spends.
 		#[pallet::constant]
 		type SpendPeriod: Get<Self::BlockNumber>;
@@ -404,7 +408,11 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 
 	/// The needed bond for a proposal whose spend is `value`.
 	fn calculate_bond(value: BalanceOf<T, I>) -> BalanceOf<T, I> {
-		T::ProposalBondMinimum::get().max(T::ProposalBond::get() * value)
+		let mut r = T::ProposalBondMinimum::get().max(T::ProposalBond::get() * value);
+		if let Some(m) = T::ProposalBondMaximum::get() {
+			r = r.min(m);
+		}
+		r
 	}
 
 	/// Spend some money! returns number of approvals before spend.

substrate/frame/treasury/src/tests.rs

@@ -115,6 +115,7 @@ impl Config for Test {
 	type OnSlash = ();
 	type ProposalBond = ProposalBond;
 	type ProposalBondMinimum = ConstU64<1>;
+	type ProposalBondMaximum = ();
 	type SpendPeriod = ConstU64<2>;
 	type Burn = Burn;
 	type BurnDestination = (); // Just gets burned.