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.)

8 files changed, 46 insertions, 13 deletions

diff --git a/src/interfaces/wallet.cpp b/src/interfaces/wallet.cpp
index 397403d308..b65eb72b1c 100644
--- a/src/interfaces/wallet.cpp
+++ b/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
     {
diff --git a/src/interfaces/wallet.h b/src/interfaces/wallet.h
index 67569a3e55..e2161521f6 100644
--- a/src/interfaces/wallet.h
+++ b/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;
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index 9e23fe78d8..0ac61f3adc 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/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
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index 671b5e1ce6..72c75f7be0 100644
--- a/src/qt/walletmodel.cpp
+++ b/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;
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index 8a2a798644..e12a98a53b 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/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
diff --git a/src/wallet/scriptpubkeyman.h b/src/wallet/scriptpubkeyman.h
index d62d30f339..9fa2a68284 100644
--- a/src/wallet/scriptpubkeyman.h
+++ b/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;
 
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 4037e23b69..e02d172111 100644
--- a/src/wallet/wallet.cpp
+++ b/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
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index cf000b0b70..9931671fb4 100644
--- a/src/wallet/wallet.h
+++ b/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