test: add constants for PSBT key types (BIP 174)

Also take use of the constants in the signet miner to get rid of
magic numbers and increase readability and maintainability.

contrib/signet/miner

@@ -20,7 +20,7 @@ sys.path.insert(0, PATH_BASE_TEST_FUNCTIONAL)
 
 from test_framework.blocktools import get_witness_script, script_BIP34_coinbase_height # noqa: E402
 from test_framework.messages import CBlock, CBlockHeader, COutPoint, CTransaction, CTxIn, CTxInWitness, CTxOut, from_binary, from_hex, ser_string, ser_uint256, tx_from_hex # noqa: E402
-from test_framework.psbt import PSBT, PSBTMap # noqa: E402
+from test_framework.psbt import PSBT, PSBTMap, PSBT_GLOBAL_UNSIGNED_TX, PSBT_IN_FINAL_SCRIPTSIG, PSBT_IN_FINAL_SCRIPTWITNESS, PSBT_IN_NON_WITNESS_UTXO, PSBT_IN_SIGHASH_TYPE # noqa: E402
 from test_framework.script import CScriptOp # noqa: E402
 
 logging.basicConfig(
@@ -74,11 +74,11 @@ def signet_txs(block, challenge):
 
 def do_createpsbt(block, signme, spendme):
     psbt = PSBT()
-    psbt.g = PSBTMap( {0: signme.serialize(),
+    psbt.g = PSBTMap( {PSBT_GLOBAL_UNSIGNED_TX: signme.serialize(),
                        PSBT_SIGNET_BLOCK: block.serialize()
                      } )
-    psbt.i = [ PSBTMap( {0: spendme.serialize(),
-                         3: bytes([1,0,0,0])})
+    psbt.i = [ PSBTMap( {PSBT_IN_NON_WITNESS_UTXO: spendme.serialize(),
+                         PSBT_IN_SIGHASH_TYPE: bytes([1,0,0,0])})
              ]
     psbt.o = [ PSBTMap() ]
     return psbt.to_base64()
@@ -90,8 +90,8 @@ def do_decode_psbt(b64psbt):
     assert len(psbt.tx.vout) == 1
     assert PSBT_SIGNET_BLOCK in psbt.g.map
 
-    scriptSig = psbt.i[0].map.get(7, b"")
-    scriptWitness = psbt.i[0].map.get(8, b"\x00")
+    scriptSig = psbt.i[0].map.get(PSBT_IN_FINAL_SCRIPTSIG, b"")
+    scriptWitness = psbt.i[0].map.get(PSBT_IN_FINAL_SCRIPTWITNESS, b"\x00")
 
     return from_binary(CBlock, psbt.g.map[PSBT_SIGNET_BLOCK]), ser_string(scriptSig) + scriptWitness
 

test/functional/test_framework/psbt.py

@@ -13,6 +13,57 @@ from .messages import (
 )
 
 
+# global types
+PSBT_GLOBAL_UNSIGNED_TX = 0x00
+PSBT_GLOBAL_XPUB = 0x01
+PSBT_GLOBAL_TX_VERSION = 0x02
+PSBT_GLOBAL_FALLBACK_LOCKTIME = 0x03
+PSBT_GLOBAL_INPUT_COUNT = 0x04
+PSBT_GLOBAL_OUTPUT_COUNT = 0x05
+PSBT_GLOBAL_TX_MODIFIABLE = 0x06
+PSBT_GLOBAL_VERSION = 0xfb
+PSBT_GLOBAL_PROPRIETARY = 0xfc
+
+# per-input types
+PSBT_IN_NON_WITNESS_UTXO = 0x00
+PSBT_IN_WITNESS_UTXO = 0x01
+PSBT_IN_PARTIAL_SIG = 0x02
+PSBT_IN_SIGHASH_TYPE = 0x03
+PSBT_IN_REDEEM_SCRIPT = 0x04
+PSBT_IN_WITNESS_SCRIPT = 0x05
+PSBT_IN_BIP32_DERIVATION = 0x06
+PSBT_IN_FINAL_SCRIPTSIG = 0x07
+PSBT_IN_FINAL_SCRIPTWITNESS = 0x08
+PSBT_IN_POR_COMMITMENT = 0x09
+PSBT_IN_RIPEMD160 = 0x0a
+PSBT_IN_SHA256 = 0x0b
+PSBT_IN_HASH160 = 0x0c
+PSBT_IN_HASH256 = 0x0d
+PSBT_IN_PREVIOUS_TXID = 0x0e
+PSBT_IN_OUTPUT_INDEX = 0x0f
+PSBT_IN_SEQUENCE = 0x10
+PSBT_IN_REQUIRED_TIME_LOCKTIME = 0x11
+PSBT_IN_REQUIRED_HEIGHT_LOCKTIME = 0x12
+PSBT_IN_TAP_KEY_SIG = 0x13
+PSBT_IN_TAP_SCRIPT_SIG = 0x14
+PSBT_IN_TAP_LEAF_SCRIPT = 0x15
+PSBT_IN_TAP_BIP32_DERIVATION = 0x16
+PSBT_IN_TAP_INTERNAL_KEY = 0x17
+PSBT_IN_TAP_MERKLE_ROOT = 0x18
+PSBT_IN_PROPRIETARY = 0xfc
+
+# per-output types
+PSBT_OUT_REDEEM_SCRIPT = 0x00
+PSBT_OUT_WITNESS_SCRIPT = 0x01
+PSBT_OUT_BIP32_DERIVATION = 0x02
+PSBT_OUT_AMOUNT = 0x03
+PSBT_OUT_SCRIPT = 0x04
+PSBT_OUT_TAP_INTERNAL_KEY = 0x05
+PSBT_OUT_TAP_TREE = 0x06
+PSBT_OUT_TAP_BIP32_DERIVATION = 0x07
+PSBT_OUT_PROPRIETARY = 0xfc
+
+
 class PSBTMap:
     """Class for serializing and deserializing PSBT maps"""