wallet: Refactor function for single DescSPKM setup

We will need access to a function that sets up a singular
DescriptorSPKM, so refactor this out of the multiple DescriptorSPKM
setup function.

Author: achow101

src/wallet/wallet.cpp

@@ -3628,6 +3628,26 @@ DescriptorScriptPubKeyMan& CWallet::LoadDescriptorScriptPubKeyMan(uint256 id, Wa
     return *spk_manager;
 }
 
+DescriptorScriptPubKeyMan& CWallet::SetupDescriptorScriptPubKeyMan(WalletBatch& batch, const CExtKey& master_key, const OutputType& output_type, bool internal)
+{
+    AssertLockHeld(cs_wallet);
+    auto spk_manager = std::unique_ptr<DescriptorScriptPubKeyMan>(new DescriptorScriptPubKeyMan(*this, m_keypool_size));
+    if (IsCrypted()) {
+        if (IsLocked()) {
+            throw std::runtime_error(std::string(__func__) + ": Wallet is locked, cannot setup new descriptors");
+        }
+        if (!spk_manager->CheckDecryptionKey(vMasterKey) && !spk_manager->Encrypt(vMasterKey, &batch)) {
+            throw std::runtime_error(std::string(__func__) + ": Could not encrypt new descriptors");
+        }
+    }
+    spk_manager->SetupDescriptorGeneration(batch, master_key, output_type, internal);
+    DescriptorScriptPubKeyMan* out = spk_manager.get();
+    uint256 id = spk_manager->GetID();
+    AddScriptPubKeyMan(id, std::move(spk_manager));
+    AddActiveScriptPubKeyManWithDb(batch, id, output_type, internal);
+    return *out;
+}
+
 void CWallet::SetupDescriptorScriptPubKeyMans(const CExtKey& master_key)
 {
     AssertLockHeld(cs_wallet);
@@ -3638,19 +3658,7 @@ void CWallet::SetupDescriptorScriptPubKeyMans(const CExtKey& master_key)
 
     for (bool internal : {false, true}) {
         for (OutputType t : OUTPUT_TYPES) {
-            auto spk_manager = std::unique_ptr<DescriptorScriptPubKeyMan>(new DescriptorScriptPubKeyMan(*this, m_keypool_size));
-            if (IsCrypted()) {
-                if (IsLocked()) {
-                    throw std::runtime_error(std::string(__func__) + ": Wallet is locked, cannot setup new descriptors");
-                }
-                if (!spk_manager->CheckDecryptionKey(vMasterKey) && !spk_manager->Encrypt(vMasterKey, &batch)) {
-                    throw std::runtime_error(std::string(__func__) + ": Could not encrypt new descriptors");
-                }
-            }
-            spk_manager->SetupDescriptorGeneration(batch, master_key, t, internal);
-            uint256 id = spk_manager->GetID();
-            AddScriptPubKeyMan(id, std::move(spk_manager));
-            AddActiveScriptPubKeyManWithDb(batch, id, t, internal);
+            SetupDescriptorScriptPubKeyMan(batch, master_key, t, internal);
         }
     }
 

src/wallet/wallet.h

@@ -1018,6 +1018,8 @@ class CWallet final : public WalletStorage, public interfaces::Chain::Notificati
     //! @param[in] internal Whether this ScriptPubKeyMan provides change addresses
     void DeactivateScriptPubKeyMan(uint256 id, OutputType type, bool internal);
 
+    //! Create new DescriptorScriptPubKeyMan and add it to the wallet
+    DescriptorScriptPubKeyMan& SetupDescriptorScriptPubKeyMan(WalletBatch& batch, const CExtKey& master_key, const OutputType& output_type, bool internal) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     //! Create new DescriptorScriptPubKeyMans and add them to the wallet
     void SetupDescriptorScriptPubKeyMans(const CExtKey& master_key) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     void SetupDescriptorScriptPubKeyMans() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);