Merge #17219: wallet: allow transaction without change if keypool is empty

92bcd70808b9cac56b184903aa6d37baf9641b37 [wallet] allow transaction without change if keypool is empty (Sjors Provoost)
709f8685ac37510aa145ac259753583c82280038 [wallet] CreateTransaction: simplify change address check (Sjors Provoost)
5efc25f9638866941028454cfa9bae27f1519cb4 [wallet] translate "Keypool ran out" message (Sjors Provoost)

Pull request description:

  Extracted from #16944

  First this PR simplifies the check when generating a change address, by dropping `CanGetAddresses` and just letting `reservedest.GetReservedDestination` do this check.

  Second, when the keypool is empty, instead of immediately giving up, we create a dummy change address and pass that to coin selection. If we didn't need the change address (e.g. when spending the entire balance), then it's all good. If we did need a change address, we throw the original error.

ACKs for top commit:
  fjahr:
    Code review ACK 92bcd70808b9cac56b184903aa6d37baf9641b37
  jonasschnelli:
    utACK 92bcd70808b9cac56b184903aa6d37baf9641b37
  achow101:
    ACK 92bcd70808b9cac56b184903aa6d37baf9641b37
  meshcollider:
    Code review ACK 92bcd70808b9cac56b184903aa6d37baf9641b37

Tree-SHA512: 07b8c8251f57061c58a85ebf0359be63583c23bac7a2c4cefdc14820c0cdebcc90a2bb218e5ede0db11d1e204cda149e056dfd18614642070b3d56efe2735006

2 files changed, 12 insertions, 13 deletions

diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index aa81ebe2fd..ec75f06e5e 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -20,7 +20,7 @@ bool LegacyScriptPubKeyMan::GetNewDestination(const OutputType type, CTxDestinat
     // Generate a new key that is added to wallet
     CPubKey new_key;
     if (!GetKeyFromPool(new_key, type)) {
-        error = "Error: Keypool ran out, please call keypoolrefill first";
+        error = _("Error: Keypool ran out, please call keypoolrefill first").translated;
         return false;
     }
     LearnRelatedScripts(new_key, type);
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index feb0563409..4ba74f7f92 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2770,20 +2770,14 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
                 //  rediscover unknown transactions that were written with keys of ours to recover
                 //  post-backup change.
 
-                // Reserve a new key pair from key pool
-                if (!CanGetAddresses(true)) {
-                    strFailReason = _("Can't generate a change-address key. No keys in the internal keypool and can't generate any keys.").translated;
-                    return false;
-                }
+                // Reserve a new key pair from key pool. If it fails, provide a dummy
+                // destination in case we don't need change.
                 CTxDestination dest;
-                bool ret = reservedest.GetReservedDestination(dest, true);
-                if (!ret)
-                {
-                    strFailReason = "Keypool ran out, please call keypoolrefill first";
-                    return false;
+                if (!reservedest.GetReservedDestination(dest, true)) {
+                    strFailReason = _("Transaction needs a change address, but we can't generate it. Please call keypoolrefill first.").translated;
                 }
-
                 scriptChange = GetScriptForDestination(dest);
+                assert(!dest.empty() || scriptChange.empty());
             }
             CTxOut change_prototype_txout(0, scriptChange);
             coin_selection_params.change_output_size = GetSerializeSize(change_prototype_txout);
@@ -2999,6 +2993,11 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
                 coin_selection_params.use_bnb = false;
                 continue;
             }
+
+            // Give up if change keypool ran out and we failed to find a solution without change:
+            if (scriptChange.empty() && nChangePosInOut != -1) {
+                return false;
+            }
         }
 
         // Shuffle selected coins and fill in final vin
@@ -3294,7 +3293,7 @@ bool CWallet::GetNewChangeDestination(const OutputType type, CTxDestination& des
 
     ReserveDestination reservedest(this, type);
     if (!reservedest.GetReservedDestination(dest, true)) {
-        error = "Error: Keypool ran out, please call keypoolrefill first";
+        error = _("Error: Keypool ran out, please call keypoolrefill first").translated;
         return false;
     }