FillPSBT: report number of inputs signed (or would sign)

In FillPSBT, optionally report the number of inputs we successfully
signed, as an out parameter. If "sign" is false, instead report the
number of inputs for which GetSigningProvider does not return nullptr.
(This is a potentially overbroad estimate of inputs we could sign.)

src/interfaces/wallet.cpp

@@ -335,9 +335,10 @@ public:
         bool sign,
         bool bip32derivs,
         PartiallySignedTransaction& psbtx,
-        bool& complete) override
+        bool& complete,
+        size_t* n_signed) override
     {
-        return m_wallet->FillPSBT(psbtx, complete, sighash_type, sign, bip32derivs);
+        return m_wallet->FillPSBT(psbtx, complete, sighash_type, sign, bip32derivs, n_signed);
     }
     WalletBalances getBalances() override
     {

src/interfaces/wallet.h

@@ -197,7 +197,8 @@ public:
         bool sign,
         bool bip32derivs,
         PartiallySignedTransaction& psbtx,
-        bool& complete) = 0;
+        bool& complete,
+        size_t* n_signed) = 0;
 
     //! Get balances.
     virtual WalletBalances getBalances() = 0;

src/qt/sendcoinsdialog.cpp

@@ -392,7 +392,7 @@ void SendCoinsDialog::on_sendButton_clicked()
         CMutableTransaction mtx = CMutableTransaction{*(m_current_transaction->getWtx())};
         PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
-        const TransactionError err = model->wallet().fillPSBT(SIGHASH_ALL, false /* sign */, true /* bip32derivs */, psbtx, complete);
+        const TransactionError err = model->wallet().fillPSBT(SIGHASH_ALL, false /* sign */, true /* bip32derivs */, psbtx, complete, nullptr);
         assert(!complete);
         assert(err == TransactionError::OK);
         // Serialize the PSBT

src/qt/walletmodel.cpp

@@ -536,7 +536,7 @@ bool WalletModel::bumpFee(uint256 hash, uint256& new_hash)
     if (create_psbt) {
         PartiallySignedTransaction psbtx(mtx);
         bool complete = false;
-        const TransactionError err = wallet().fillPSBT(SIGHASH_ALL, false /* sign */, true /* bip32derivs */, psbtx, complete);
+        const TransactionError err = wallet().fillPSBT(SIGHASH_ALL, false /* sign */, true /* bip32derivs */, psbtx, complete, nullptr);
         if (err != TransactionError::OK || complete) {
             QMessageBox::critical(nullptr, tr("Fee bump error"), tr("Can't draft transaction."));
             return false;

src/wallet/scriptpubkeyman.cpp

@@ -585,8 +585,11 @@ SigningResult LegacyScriptPubKeyMan::SignMessage(const std::string& message, con
     return SigningResult::SIGNING_FAILED;
 }
 
-TransactionError LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs) const
+TransactionError LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs, int* n_signed) const
 {
+    if (n_signed) {
+        *n_signed = 0;
+    }
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
         const CTxIn& txin = psbtx.tx->vin[i];
         PSBTInput& input = psbtx.inputs.at(i);
@@ -617,6 +620,14 @@ TransactionError LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psb
         SignatureData sigdata;
         input.FillSignatureData(sigdata);
         SignPSBTInput(HidingSigningProvider(this, !sign, !bip32derivs), psbtx, i, sighash_type);
+
+        bool signed_one = PSBTInputSigned(input);
+        if (n_signed && (signed_one || !sign)) {
+            // If sign is false, we assume that we _could_ sign if we get here. This
+            // will never have false negatives; it is hard to tell under what i
+            // circumstances it could have false positives.
+            (*n_signed)++;
+        }
     }
 
     // Fill in the bip32 keypaths and redeemscripts for the outputs so that hardware wallets can identify change
@@ -2064,8 +2075,11 @@ SigningResult DescriptorScriptPubKeyMan::SignMessage(const std::string& message,
     return SigningResult::OK;
 }
 
-TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs) const
+TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs, int* n_signed) const
 {
+    if (n_signed) {
+        *n_signed = 0;
+    }
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
         const CTxIn& txin = psbtx.tx->vin[i];
         PSBTInput& input = psbtx.inputs.at(i);
@@ -2117,6 +2131,14 @@ TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction&
         }
 
         SignPSBTInput(HidingSigningProvider(keys.get(), !sign, !bip32derivs), psbtx, i, sighash_type);
+
+        bool signed_one = PSBTInputSigned(input);
+        if (n_signed && (signed_one || !sign)) {
+            // If sign is false, we assume that we _could_ sign if we get here. This
+            // will never have false negatives; it is hard to tell under what i
+            // circumstances it could have false positives.
+            (*n_signed)++;
+        }
     }
 
     // Fill in the bip32 keypaths and redeemscripts for the outputs so that hardware wallets can identify change

src/wallet/scriptpubkeyman.h

@@ -234,7 +234,7 @@ public:
     /** Sign a message with the given script */
     virtual SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const { return SigningResult::SIGNING_FAILED; };
     /** Adds script and derivation path information to a PSBT, and optionally signs it. */
-    virtual TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false) const { return TransactionError::INVALID_PSBT; }
+    virtual TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const { return TransactionError::INVALID_PSBT; }
 
     virtual uint256 GetID() const { return uint256(); }
 
@@ -393,7 +393,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, std::string>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
-    TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false) const override;
+    TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const override;
 
     uint256 GetID() const override;
 
@@ -596,7 +596,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, std::string>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
-    TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false) const override;
+    TransactionError FillPSBT(PartiallySignedTransaction& psbt, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr) const override;
 
     uint256 GetID() const override;
 

src/wallet/wallet.cpp

@@ -2471,8 +2471,11 @@ bool CWallet::SignTransaction(CMutableTransaction& tx, const std::map<COutPoint,
     return false;
 }
 
-TransactionError CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& complete, int sighash_type, bool sign, bool bip32derivs) const
+TransactionError CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& complete, int sighash_type, bool sign, bool bip32derivs, size_t * n_signed) const
 {
+    if (n_signed) {
+        *n_signed = 0;
+    }
     LOCK(cs_wallet);
     // Get all of the previous transactions
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
@@ -2503,10 +2506,15 @@ TransactionError CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& comp
 
     // Fill in information from ScriptPubKeyMans
     for (ScriptPubKeyMan* spk_man : GetAllScriptPubKeyMans()) {
-        TransactionError res = spk_man->FillPSBT(psbtx, sighash_type, sign, bip32derivs);
+        int n_signed_this_spkm = 0;
+        TransactionError res = spk_man->FillPSBT(psbtx, sighash_type, sign, bip32derivs, &n_signed_this_spkm);
         if (res != TransactionError::OK) {
             return res;
         }
+
+        if (n_signed) {
+            (*n_signed) += n_signed_this_spkm;
+        }
     }
 
     // Complete if every input is now signed

src/wallet/wallet.h

@@ -964,7 +964,8 @@ public:
                   bool& complete,
                   int sighash_type = 1 /* SIGHASH_ALL */,
                   bool sign = true,
-                  bool bip32derivs = true) const;
+                  bool bip32derivs = true,
+                  size_t* n_signed = nullptr) const;
 
     /**
      * Create a new transaction paying the recipients with a set of coins