Merge bitcoin/bitcoin#25656: refactor: wallet: return util::Result from GetReservedDestination methods

76b3c37fcb refactor: wallet: return util::Result from `GetReservedDestination` methods (Sebastian Falbesoner)

Pull request description:

  This PR is a follow-up to #25218, as suggested in comment https://github.com/bitcoin/bitcoin/pull/25218#discussion_r907710067. The interfaces of the methods `ReserveDestination::GetReservedDestination`, `{Legacy,Descriptor,}ScriptPubKeyMan::GetReservedDestination` are improved by returning `util::Result<CTxDestination>` instead of `bool` in order to get rid of the two `CTxDestination&` and `bilingual_str&` out-parameters.

ACKs for top commit:
  furszy:
    ACK 76b3c37f

Tree-SHA512: bf15560a88d645bcf8768024013d36012cd65caaa4a613e8a055dfd8f29cb4a219c19084606992bad177920cdca3a732ec168e9b9526f9295491f2cf79cc6815

src/wallet/scriptpubkeyman.cpp

@@ -292,26 +292,22 @@ bool LegacyScriptPubKeyMan::Encrypt(const CKeyingMaterial& master_key, WalletBat
     return true;
 }
 
-bool LegacyScriptPubKeyMan::GetReservedDestination(const OutputType type, bool internal, CTxDestination& address, int64_t& index, CKeyPool& keypool, bilingual_str& error)
+util::Result<CTxDestination> LegacyScriptPubKeyMan::GetReservedDestination(const OutputType type, bool internal, int64_t& index, CKeyPool& keypool)
 {
     if (LEGACY_OUTPUT_TYPES.count(type) == 0) {
-        error = _("Error: Legacy wallets only support the \"legacy\", \"p2sh-segwit\", and \"bech32\" address types");
+        return util::Error{_("Error: Legacy wallets only support the \"legacy\", \"p2sh-segwit\", and \"bech32\" address types")};
-        return false;
     }
     assert(type != OutputType::BECH32M);
 
     LOCK(cs_KeyStore);
     if (!CanGetAddresses(internal)) {
-        error = _("Error: Keypool ran out, please call keypoolrefill first");
+        return util::Error{_("Error: Keypool ran out, please call keypoolrefill first")};
-        return false;
     }
 
     if (!ReserveKeyFromKeyPool(index, keypool, internal)) {
-        error = _("Error: Keypool ran out, please call keypoolrefill first");
+        return util::Error{_("Error: Keypool ran out, please call keypoolrefill first")};
-        return false;
     }
-    address = GetDestinationForKey(keypool.vchPubKey, type);
+    return GetDestinationForKey(keypool.vchPubKey, type);
-    return true;
 }
 
 bool LegacyScriptPubKeyMan::TopUpInactiveHDChain(const CKeyID seed_id, int64_t index, bool internal)
@@ -1760,17 +1756,12 @@ bool DescriptorScriptPubKeyMan::Encrypt(const CKeyingMaterial& master_key, Walle
     return true;
 }
 
-bool DescriptorScriptPubKeyMan::GetReservedDestination(const OutputType type, bool internal, CTxDestination& address, int64_t& index, CKeyPool& keypool, bilingual_str& error)
+util::Result<CTxDestination> DescriptorScriptPubKeyMan::GetReservedDestination(const OutputType type, bool internal, int64_t& index, CKeyPool& keypool)
 {
     LOCK(cs_desc_man);
     auto op_dest = GetNewDestination(type);
     index = m_wallet_descriptor.next_index - 1;
-    if (op_dest) {
+    return op_dest;
-        address = *op_dest;
-    } else {
-        error = util::ErrorString(op_dest);
-    }
-    return bool(op_dest);
 }
 
 void DescriptorScriptPubKeyMan::ReturnDestination(int64_t index, bool internal, const CTxDestination& addr)

src/wallet/scriptpubkeyman.h

@@ -179,7 +179,7 @@ public:
     virtual bool CheckDecryptionKey(const CKeyingMaterial& master_key, bool accept_no_keys = false) { return false; }
     virtual bool Encrypt(const CKeyingMaterial& master_key, WalletBatch* batch) { return false; }
 
-    virtual bool GetReservedDestination(const OutputType type, bool internal, CTxDestination& address, int64_t& index, CKeyPool& keypool, bilingual_str& error) { return false; }
+    virtual util::Result<CTxDestination> GetReservedDestination(const OutputType type, bool internal, int64_t& index, CKeyPool& keypool) { return util::Error{Untranslated("Not supported")}; }
     virtual void KeepDestination(int64_t index, const OutputType& type) {}
     virtual void ReturnDestination(int64_t index, bool internal, const CTxDestination& addr) {}
 
@@ -366,7 +366,7 @@ public:
     bool CheckDecryptionKey(const CKeyingMaterial& master_key, bool accept_no_keys = false) override;
     bool Encrypt(const CKeyingMaterial& master_key, WalletBatch* batch) override;
 
-    bool GetReservedDestination(const OutputType type, bool internal, CTxDestination& address, int64_t& index, CKeyPool& keypool, bilingual_str& error) override;
+    util::Result<CTxDestination> GetReservedDestination(const OutputType type, bool internal, int64_t& index, CKeyPool& keypool) override;
     void KeepDestination(int64_t index, const OutputType& type) override;
     void ReturnDestination(int64_t index, bool internal, const CTxDestination&) override;
 
@@ -576,7 +576,7 @@ public:
     bool CheckDecryptionKey(const CKeyingMaterial& master_key, bool accept_no_keys = false) override;
     bool Encrypt(const CKeyingMaterial& master_key, WalletBatch* batch) override;
 
-    bool GetReservedDestination(const OutputType type, bool internal, CTxDestination& address, int64_t& index, CKeyPool& keypool, bilingual_str& error) override;
+    util::Result<CTxDestination> GetReservedDestination(const OutputType type, bool internal, int64_t& index, CKeyPool& keypool) override;
     void ReturnDestination(int64_t index, bool internal, const CTxDestination& addr) override;
 
     // Tops up the descriptor cache and m_map_script_pub_keys. The cache is stored in the wallet file

src/wallet/spend.cpp

@@ -814,11 +814,13 @@ static util::Result<CreatedTransactionResult> CreateTransactionInternal(
         // Reserve a new key pair from key pool. If it fails, provide a dummy
         // destination in case we don't need change.
         CTxDestination dest;
-        bilingual_str dest_err;
+        auto op_dest = reservedest.GetReservedDestination(true);
-        if (!reservedest.GetReservedDestination(dest, true, dest_err)) {
+        if (!op_dest) {
-            error = _("Transaction needs a change address, but we can't generate it.") + Untranslated(" ") + dest_err;
+            error = _("Transaction needs a change address, but we can't generate it.") + Untranslated(" ") + util::ErrorString(op_dest);
+        } else {
+            dest = *op_dest;
+            scriptChange = GetScriptForDestination(dest);
         }
-        scriptChange = GetScriptForDestination(dest);
         // A valid destination implies a change script (and
         // vice-versa). An empty change script will abort later, if the
         // change keypool ran out, but change is required.

src/wallet/wallet.cpp

@@ -2359,15 +2359,11 @@ util::Result<CTxDestination> CWallet::GetNewChangeDestination(const OutputType t
 {
     LOCK(cs_wallet);
 
-    CTxDestination dest;
-    bilingual_str error;
     ReserveDestination reservedest(this, type);
-    if (!reservedest.GetReservedDestination(dest, true, error)) {
+    auto op_dest = reservedest.GetReservedDestination(true);
-        return util::Error{error};
+    if (op_dest) reservedest.KeepDestination();
-    }
 
-    reservedest.KeepDestination();
+    return op_dest;
-    return dest;
 }
 
 std::optional<int64_t> CWallet::GetOldestKeyPoolTime() const
@@ -2437,27 +2433,24 @@ std::set<std::string> CWallet::ListAddrBookLabels(const std::string& purpose) co
     return label_set;
 }
 
-bool ReserveDestination::GetReservedDestination(CTxDestination& dest, bool internal, bilingual_str& error)
+util::Result<CTxDestination> ReserveDestination::GetReservedDestination(bool internal)
 {
     m_spk_man = pwallet->GetScriptPubKeyMan(type, internal);
     if (!m_spk_man) {
-        error = strprintf(_("Error: No %s addresses available."), FormatOutputType(type));
+        return util::Error{strprintf(_("Error: No %s addresses available."), FormatOutputType(type))};
-        return false;
     }
 
-
     if (nIndex == -1)
     {
         m_spk_man->TopUp();
 
         CKeyPool keypool;
-        if (!m_spk_man->GetReservedDestination(type, internal, address, nIndex, keypool, error)) {
+        auto op_address = m_spk_man->GetReservedDestination(type, internal, nIndex, keypool);
-            return false;
+        if (!op_address) return op_address;
-        }
+        address = *op_address;
         fInternal = keypool.fInternal;
     }
-    dest = address;
+    return address;
-    return true;
 }
 
 void ReserveDestination::KeepDestination()

src/wallet/wallet.h

@@ -191,7 +191,7 @@ public:
     }
 
     //! Reserve an address
-    bool GetReservedDestination(CTxDestination& pubkey, bool internal, bilingual_str& error);
+    util::Result<CTxDestination> GetReservedDestination(bool internal);
     //! Return reserved address
     void ReturnDestination();
     //! Keep the address. Do not return it's key to the keypool when this object goes out of scope