Exposed some detail about where assets are coming from and where they…

… are going.

masp_primitives/src/transaction/builder.rs

@@ -153,7 +153,7 @@ impl<P, R, K, N> Builder<P, R, K, N> {
 
     /// Returns the set of Sapling inputs currently committed to be consumed
     /// by the transaction.
-    pub fn sapling_inputs(&self) -> &[impl sapling::fees::InputView<()>] {
+    pub fn sapling_inputs(&self) -> &[impl sapling::fees::InputView<(), K>] {
         self.sapling_builder.inputs()
     }
 

masp_primitives/src/transaction/components/sapling/builder.rs

@@ -103,7 +103,7 @@ impl<Key: BorshDeserialize> BorshDeserialize for SpendDescriptionInfo<Key> {
     }
 }
 
-impl<K> fees::InputView<()> for SpendDescriptionInfo<K> {
+impl<K> fees::InputView<(), K> for SpendDescriptionInfo<K> {
     fn note_id(&self) -> &() {
         // The builder does not make use of note identifiers, so we can just return the unit value.
         &()
@@ -116,6 +116,10 @@ impl<K> fees::InputView<()> for SpendDescriptionInfo<K> {
     fn asset_type(&self) -> AssetType {
         self.note.asset_type
     }
+
+    fn key(&self) -> &K {
+        &self.extsk
+    }
 }
 
 /// A struct containing the information required in order to construct a
@@ -207,6 +211,10 @@ impl fees::OutputView for SaplingOutputInfo {
     fn asset_type(&self) -> AssetType {
         self.note.asset_type
     }
+
+    fn address(&self) -> PaymentAddress {
+        self.to
+    }
 }
 
 /// Metadata about a transaction created by a [`SaplingBuilder`].
@@ -349,7 +357,7 @@ impl<P, K> SaplingBuilder<P, K> {
 
     /// Returns the list of Sapling inputs that will be consumed by the transaction being
     /// constructed.
-    pub fn inputs(&self) -> &[impl fees::InputView<()>] {
+    pub fn inputs(&self) -> &[impl fees::InputView<(), K>] {
         &self.spends
     }
 

masp_primitives/src/transaction/components/sapling/fees.rs

@@ -2,16 +2,19 @@
 //! of a transaction.
 
 use crate::asset_type::AssetType;
+use crate::sapling::PaymentAddress;
 
 /// A trait that provides a minimized view of a Sapling input suitable for use in
 /// fee and change calculation.
-pub trait InputView<NoteRef> {
+pub trait InputView<NoteRef, Key> {
     /// An identifier for the input being spent.
     fn note_id(&self) -> &NoteRef;
     /// The value of the input being spent.
     fn value(&self) -> u64;
     /// The asset type of the input being spent.
     fn asset_type(&self) -> AssetType;
+    /// The spend/view key of the input being spent.
+    fn key(&self) -> &Key;
 }
 
 /// A trait that provides a minimized view of a Sapling output suitable for use in
@@ -21,4 +24,6 @@ pub trait OutputView {
     fn value(&self) -> u64;
     /// The asset type of the output being produced.
     fn asset_type(&self) -> AssetType;
+    /// The destination of this output
+    fn address(&self) -> PaymentAddress;
 }