Merge bitcoin/bitcoin#22514: psbt: Actually use SIGHASH_DEFAULT for PSBT signing

c0405ee27fa23a9868f04c052bdc94d7accc57e2 rpc: Document that DEFAULT is for Taproot, ALL for everything else (Andrew Chow)
d3992669df826899a3de78a77a366dab46028026 psbt: Actually use SIGHASH_DEFAULT (Andrew Chow)
eb9a1a2c595a03475fd4275b104676b7e2200f07 psbt: Make sighash_type std::optional<int> (Andrew Chow)

Pull request description:

  Make the behavior align with the help text by actually using SIGHASH_DEFAULT as the default sighash for signing PSBTs.

ACKs for top commit:
  Sjors:
    re-utACK c0405ee27fa23a9868f04c052bdc94d7accc57e2

Tree-SHA512: 5199fb41de416b2f10ac451f824e7c94b428ba11fdb9e50f0027c692e959ce5813a340c34a4e52d7aa128e12008303d80939a693eff36a869720e45442119828

4 files changed, 8 insertions, 8 deletions

diff --git a/src/wallet/rpc/spend.cpp b/src/wallet/rpc/spend.cpp
index a92ecd37db..978174b340 100644
--- a/src/wallet/rpc/spend.cpp
+++ b/src/wallet/rpc/spend.cpp
@@ -709,7 +709,7 @@ RPCHelpMan signrawtransactionwithwallet()
                             },
                         },
                     },
-                    {"sighashtype", RPCArg::Type::STR, RPCArg::Default{"DEFAULT"}, "The signature hash type. Must be one of\n"
+                    {"sighashtype", RPCArg::Type::STR, RPCArg::Default{"DEFAULT for Taproot, ALL otherwise"}, "The signature hash type. Must be one of\n"
             "       \"DEFAULT\"\n"
             "       \"ALL\"\n"
             "       \"NONE\"\n"
@@ -1167,7 +1167,7 @@ RPCHelpMan walletprocesspsbt()
                 {
                     {"psbt", RPCArg::Type::STR, RPCArg::Optional::NO, "The transaction base64 string"},
                     {"sign", RPCArg::Type::BOOL, RPCArg::Default{true}, "Also sign the transaction when updating (requires wallet to be unlocked)"},
-                    {"sighashtype", RPCArg::Type::STR, RPCArg::Default{"DEFAULT"}, "The signature hash type to sign with if not specified by the PSBT. Must be one of\n"
+                    {"sighashtype", RPCArg::Type::STR, RPCArg::Default{"DEFAULT for Taproot, ALL otherwise"}, "The signature hash type to sign with if not specified by the PSBT. Must be one of\n"
             "       \"DEFAULT\"\n"
             "       \"ALL\"\n"
             "       \"NONE\"\n"
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index 1769429efe..a9e2624188 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -633,7 +633,7 @@ TransactionError LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psb
         }
 
         // Get the Sighash type
-        if (sign && input.sighash_type > 0 && input.sighash_type != sighash_type) {
+        if (sign && input.sighash_type != std::nullopt && *input.sighash_type != sighash_type) {
             return TransactionError::SIGHASH_MISMATCH;
         }
 
@@ -2114,7 +2114,7 @@ TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction&
         }
 
         // Get the Sighash type
-        if (sign && input.sighash_type > 0 && input.sighash_type != sighash_type) {
+        if (sign && input.sighash_type != std::nullopt && *input.sighash_type != sighash_type) {
             return TransactionError::SIGHASH_MISMATCH;
         }
 
diff --git a/src/wallet/scriptpubkeyman.h b/src/wallet/scriptpubkeyman.h
index ebe064fa0a..dda31d2c0b 100644
--- a/src/wallet/scriptpubkeyman.h
+++ b/src/wallet/scriptpubkeyman.h
@@ -236,7 +236,7 @@ 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, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const { return TransactionError::INVALID_PSBT; }
+    virtual TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const { return TransactionError::INVALID_PSBT; }
 
     virtual uint256 GetID() const { return uint256(); }
 
@@ -400,7 +400,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, bilingual_str>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
-    TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
+    TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
 
     uint256 GetID() const override;
 
@@ -609,7 +609,7 @@ public:
 
     bool SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, bilingual_str>& input_errors) const override;
     SigningResult SignMessage(const std::string& message, const PKHash& pkhash, std::string& str_sig) const override;
-    TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = 1 /* SIGHASH_ALL */, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
+    TransactionError FillPSBT(PartiallySignedTransaction& psbt, const PrecomputedTransactionData& txdata, int sighash_type = SIGHASH_DEFAULT, bool sign = true, bool bip32derivs = false, int* n_signed = nullptr, bool finalize = true) const override;
 
     uint256 GetID() const override;
 
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index dbf0f6375d..93150cc583 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -561,7 +561,7 @@ public:
      */
     TransactionError FillPSBT(PartiallySignedTransaction& psbtx,
                   bool& complete,
-                  int sighash_type = 1 /* SIGHASH_ALL */,
+                  int sighash_type = SIGHASH_DEFAULT,
                   bool sign = true,
                   bool bip32derivs = true,
                   size_t* n_signed = nullptr,