wallet: Introduce a callback called after TopUp completes

After TopUp completes, the wallet containing each SPKM will want to know
what new scriptPubKeys were generated. In order for all TopUp calls
(including ones internal the the SPKM), we use a callback function in
the WalletStorage interface.

src/wallet/scriptpubkeyman.cpp

@@ -1290,6 +1290,9 @@ bool LegacyScriptPubKeyMan::TopUp(unsigned int kpSize)
     }
     if (!batch.TxnCommit()) throw std::runtime_error(strprintf("Error during keypool top up. Cannot commit changes for wallet %s", m_storage.GetDisplayName()));
     NotifyCanGetAddressesChanged();
+    // Note: Unlike with DescriptorSPKM, LegacySPKM does not need to call
+    // m_storage.TopUpCallback() as we do not know what new scripts the LegacySPKM is
+    // watching for. CWallet's scriptPubKey cache is not used for LegacySPKMs.
     return true;
 }
 
@@ -2154,6 +2157,7 @@ bool DescriptorScriptPubKeyMan::TopUp(unsigned int size)
 bool DescriptorScriptPubKeyMan::TopUpWithDB(WalletBatch& batch, unsigned int size)
 {
     LOCK(cs_desc_man);
+    std::set<CScript> new_spks;
     unsigned int target_size;
     if (size > 0) {
         target_size = size;
@@ -2184,6 +2188,7 @@ bool DescriptorScriptPubKeyMan::TopUpWithDB(WalletBatch& batch, unsigned int siz
             if (!m_wallet_descriptor.descriptor->Expand(i, provider, scripts_temp, out_keys, &temp_cache)) return false;
         }
         // Add all of the scriptPubKeys to the scriptPubKey set
+        new_spks.insert(scripts_temp.begin(), scripts_temp.end());
         for (const CScript& script : scripts_temp) {
             m_map_script_pub_keys[script] = i;
         }
@@ -2209,6 +2214,7 @@ bool DescriptorScriptPubKeyMan::TopUpWithDB(WalletBatch& batch, unsigned int siz
     // By this point, the cache size should be the size of the entire range
     assert(m_wallet_descriptor.range_end - 1 == m_max_cached_index);
 
+    m_storage.TopUpCallback(new_spks, this);
     NotifyCanGetAddressesChanged();
     return true;
 }
@@ -2624,6 +2630,7 @@ uint256 DescriptorScriptPubKeyMan::GetID() const
 void DescriptorScriptPubKeyMan::SetCache(const DescriptorCache& cache)
 {
     LOCK(cs_desc_man);
+    std::set<CScript> new_spks;
     m_wallet_descriptor.cache = cache;
     for (int32_t i = m_wallet_descriptor.range_start; i < m_wallet_descriptor.range_end; ++i) {
         FlatSigningProvider out_keys;
@@ -2632,6 +2639,7 @@ void DescriptorScriptPubKeyMan::SetCache(const DescriptorCache& cache)
             throw std::runtime_error("Error: Unable to expand wallet descriptor from cache");
         }
         // Add all of the scriptPubKeys to the scriptPubKey set
+        new_spks.insert(scripts_temp.begin(), scripts_temp.end());
         for (const CScript& script : scripts_temp) {
             if (m_map_script_pub_keys.count(script) != 0) {
                 throw std::runtime_error(strprintf("Error: Already loaded script at index %d as being at index %d", i, m_map_script_pub_keys[script]));
@@ -2649,6 +2657,8 @@ void DescriptorScriptPubKeyMan::SetCache(const DescriptorCache& cache)
         }
         m_max_cached_index++;
     }
+    // Make sure the wallet knows about our new spks
+    m_storage.TopUpCallback(new_spks, this);
 }
 
 bool DescriptorScriptPubKeyMan::AddKey(const CKeyID& key_id, const CKey& key)

src/wallet/scriptpubkeyman.h

@@ -31,6 +31,7 @@ struct bilingual_str;
 
 namespace wallet {
 struct MigrationData;
+class ScriptPubKeyMan;
 
 // Wallet storage things that ScriptPubKeyMans need in order to be able to store things to the wallet database.
 // It provides access to things that are part of the entire wallet and not specific to a ScriptPubKeyMan such as
@@ -51,6 +52,8 @@ public:
     virtual bool WithEncryptionKey(std::function<bool (const CKeyingMaterial&)> cb) const = 0;
     virtual bool HasEncryptionKeys() const = 0;
     virtual bool IsLocked() const = 0;
+    //! Callback function for after TopUp completes containining any scripts that were added by a SPKMan
+    virtual void TopUpCallback(const std::set<CScript>&, ScriptPubKeyMan*) = 0;
 };
 
 //! Constant representing an unknown spkm creation time

src/wallet/wallet.cpp

@@ -4334,4 +4334,14 @@ util::Result<MigrationResult> MigrateLegacyToDescriptor(const std::string& walle
     }
     return res;
 }
+
+void CWallet::CacheNewScriptPubKeys(const std::set<CScript>& spks, ScriptPubKeyMan* spkm)
+{
+}
+
+void CWallet::TopUpCallback(const std::set<CScript>& spks, ScriptPubKeyMan* spkm)
+{
+    // Update scriptPubKey cache
+    CacheNewScriptPubKeys(spks, spkm);
+}
 } // namespace wallet

src/wallet/wallet.h

@@ -1042,6 +1042,11 @@ public:
 
     //! Whether the (external) signer performs R-value signature grinding
     bool CanGrindR() const;
+
+    //! Add scriptPubKeys for this ScriptPubKeyMan into the scriptPubKey cache
+    void CacheNewScriptPubKeys(const std::set<CScript>& spks, ScriptPubKeyMan* spkm);
+
+    void TopUpCallback(const std::set<CScript>& spks, ScriptPubKeyMan* spkm) override;
 };
 
 /**