psbt: add tx input and output fields in PSBTInput and PSBTOutput

PSBTInput should be aware of the previous txid, output index, and
sequence numbers for inputs, extracting them from the global
unsigned tx.

PSBTOutput should be aware of the output amount and script, extracting
them from the global unsigned tx.

This prepares for PSBTv2 where these fields are serialized.

src/psbt.cpp

@@ -15,8 +15,14 @@ using common::PSBTError;
 
 PartiallySignedTransaction::PartiallySignedTransaction(const CMutableTransaction& tx) : tx(tx)
 {
-    inputs.resize(tx.vin.size(), PSBTInput(GetVersion()));
-    outputs.resize(tx.vout.size(), PSBTOutput(GetVersion()));
+    inputs.reserve(tx.vin.size());
+    for (const CTxIn& input : tx.vin) {
+        inputs.emplace_back(GetVersion(), input.prevout.hash, input.prevout.n, input.nSequence);
+    }
+    outputs.reserve(tx.vout.size());
+    for (const CTxOut& output : tx.vout) {
+        outputs.emplace_back(GetVersion(), output.nValue, output.scriptPubKey);
+    }
 }
 
 bool PartiallySignedTransaction::IsNull() const

src/psbt.h

@@ -280,6 +280,10 @@ public:
     std::map<uint160, std::vector<unsigned char>> hash160_preimages;
     std::map<uint256, std::vector<unsigned char>> hash256_preimages;
 
+    Txid prev_txid;
+    uint32_t prev_out;
+    std::optional<uint32_t> sequence;
+
     // Taproot fields
     std::vector<unsigned char> m_tap_key_sig;
     std::map<std::pair<XOnlyPubKey, uint256>, std::vector<unsigned char>> m_tap_script_sigs;
@@ -304,8 +308,11 @@ public:
     void FromSignatureData(const SignatureData& sigdata);
     void Merge(const PSBTInput& input);
     uint32_t GetVersion() const { return m_psbt_version; }
-    explicit PSBTInput(uint32_t psbt_version)
-        : m_psbt_version(psbt_version)
+    explicit PSBTInput(uint32_t psbt_version, const Txid& prev_txid, uint32_t prev_out, std::optional<uint32_t> sequence = std::nullopt)
+        : m_psbt_version(psbt_version),
+        prev_txid(prev_txid),
+        prev_out(prev_out),
+        sequence(sequence)
     {
         assert(m_psbt_version == 0);
     }
@@ -816,13 +823,18 @@ public:
     std::map<std::vector<unsigned char>, std::vector<unsigned char>> unknown;
     std::set<PSBTProprietary> m_proprietary;
 
+    CAmount amount;
+    CScript script;
+
     bool IsNull() const;
     void FillSignatureData(SignatureData& sigdata) const;
     void FromSignatureData(const SignatureData& sigdata);
     void Merge(const PSBTOutput& output);
     uint32_t GetVersion() const { return m_psbt_version; }
-    explicit PSBTOutput(uint32_t psbt_version)
-        : m_psbt_version(psbt_version)
+    explicit PSBTOutput(uint32_t psbt_version, CAmount amount, const CScript& script)
+        : m_psbt_version(psbt_version),
+        amount(amount),
+        script(script)
     {
         assert(m_psbt_version == 0);
     }
@@ -1264,7 +1276,7 @@ public:
         // Read input data
         unsigned int i = 0;
         while (!s.empty() && i < tx->vin.size()) {
-            PSBTInput input(psbt_ver);
+            PSBTInput input(psbt_ver, tx->vin[i].prevout.hash, tx->vin[i].prevout.n, tx->vin[i].nSequence);
             s >> input;
             inputs.push_back(input);
 
@@ -1287,7 +1299,7 @@ public:
         // Read output data
         i = 0;
         while (!s.empty() && i < tx->vout.size()) {
-            PSBTOutput output(psbt_ver);
+            PSBTOutput output(psbt_ver, tx->vout[i].nValue, tx->vout[i].scriptPubKey);
             s >> output;
             outputs.push_back(output);
             ++i;

src/rpc/rawtransaction.cpp

@@ -1649,14 +1649,7 @@ static RPCMethod createpsbt()
     CMutableTransaction rawTx = ConstructTransaction(request.params[0], request.params[1], request.params[2], rbf, self.Arg<uint32_t>("version"));
 
     // Make a blank psbt
-    PartiallySignedTransaction psbtx;
-    psbtx.tx = rawTx;
-    for (unsigned int i = 0; i < rawTx.vin.size(); ++i) {
-        psbtx.inputs.emplace_back(0);
-    }
-    for (unsigned int i = 0; i < rawTx.vout.size(); ++i) {
-        psbtx.outputs.emplace_back(0);
-    }
+    PartiallySignedTransaction psbtx(rawTx);
 
     // Serialize the PSBT
     DataStream ssTx{};
@@ -1717,14 +1710,7 @@ static RPCMethod converttopsbt()
     }
 
     // Make a blank psbt
-    PartiallySignedTransaction psbtx;
-    psbtx.tx = tx;
-    for (unsigned int i = 0; i < tx.vin.size(); ++i) {
-        psbtx.inputs.emplace_back(0);
-    }
-    for (unsigned int i = 0; i < tx.vout.size(); ++i) {
-        psbtx.outputs.emplace_back(0);
-    }
+    PartiallySignedTransaction psbtx(tx);
 
     // Serialize the PSBT
     DataStream ssTx{};

src/test/fuzz/deserialize.cpp

@@ -192,11 +192,11 @@ FUZZ_TARGET_DESERIALIZE(prefilled_transaction_deserialize, {
     DeserializeFromFuzzingInput(buffer, prefilled_transaction);
 })
 FUZZ_TARGET_DESERIALIZE(psbt_input_deserialize, {
-    PSBTInput psbt_input(0);
+    PSBTInput psbt_input(0, Txid{}, 0);
     DeserializeFromFuzzingInput(buffer, psbt_input);
 })
 FUZZ_TARGET_DESERIALIZE(psbt_output_deserialize, {
-    PSBTOutput psbt_output(0);
+    PSBTOutput psbt_output(0, 0, CScript());
     DeserializeFromFuzzingInput(buffer, psbt_output);
 })
 FUZZ_TARGET_DESERIALIZE(block_deserialize, {