From 42a1de5a20007050fd3169b5da1cc28962dcb258 Mon Sep 17 00:00:00 2001
From: Kris Nuttycombe <kris@nutty.land>
Date: Thu, 5 Dec 2024 09:09:21 -0700
Subject: [PATCH] Add `DiversifiableFullViewingKey::to_internal_fvk`.

This is needed in order to permit spending of internal notes after the
previous change to `Builder::add_spend`.
---
 CHANGELOG.md | 1 +
 src/zip32.rs | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4a6e53c..d3d7af6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@ and this library adheres to Rust's notion of
   - `SpendAuthorizingKey::to_bytes`
   - `SpendValidatingKey::to_bytes`
 - `sapling_crypto::value::ValueSum::to_raw`
+- `sapling_crypto::zip32::DiversifiableFullViewingKey::to_internal_fvk`
 
 ### Fixed
 - `sapling_crypto::prover::OutputProver::prepare_circuit` now takes `esk` as an
diff --git a/src/zip32.rs b/src/zip32.rs
index c2b7ea6..ea744f4 100644
--- a/src/zip32.rs
+++ b/src/zip32.rs
@@ -705,6 +705,11 @@ impl DiversifiableFullViewingKey {
         &self.fvk
     }
 
+    /// Returns the internal [`FullViewingKey`] component of this diversifiable full viewing key.
+    pub fn to_internal_fvk(&self) -> FullViewingKey {
+        self.derive_internal().fvk
+    }
+
     /// Derives a nullifier-deriving key for the provided scope.
     ///
     /// This API is provided so that nullifiers for change notes can be correctly computed.