Merge bitcoin/bitcoin#25289: test: implement 'bech32m' mode for getnewdestination() helper

dcf36fe8e3 test: implement 'bech32m' mode for `getnewdestination()` helper (Sebastian Falbesoner)
1999dcfa40 test: add helpers for creating P2TR scripts/addresses from output key (Sebastian Falbesoner)

Pull request description:

  This PR adds the missing 'bech32m' mode for the `getnewdestination()` helper and sets it as default, i.e. the function returns a tuple (output x-only-pubkey, scriptPubKey, taproot address) now if not specified otherwise. In a preparation commit, the helpers `output_key_to_p2tr{_script}` are introduced. Note that in contrast to all other common script output types, there are usually _two_ keys involved in creating a taproot output (internal key and output key), hence the prefix `output_` is used to clarify that the  output key is expected and the helpers don't do any key tweaking.

  Thanks to michaelfolkson (for pointing out this TODO that I forgot about) and sipa (for patiently explaining basic things about BIP341).

ACKs for top commit:
  michaelfolkson:
    ACK dcf36fe8e3
  w0xlt:
    reACK dcf36fe8e3

Tree-SHA512: 5bb8d5fd96c63092ede10c3f022ffb2e13c14e333c4aa73348d95deb70cbf0a74745218dc4a7c419eb846793dd69e8217a7b4332a13ae2b2758e100b51fb1a9f

test/functional/test_framework/address.py

@@ -47,8 +47,7 @@ def create_deterministic_address_bcrt1_p2tr_op_true():
     Returns a tuple with the generated address and the internal key.
     """
     internal_key = (1).to_bytes(32, 'big')
-    scriptPubKey = taproot_construct(internal_key, [(None, CScript([OP_TRUE]))]).scriptPubKey
-    address = encode_segwit_address("bcrt", 1, scriptPubKey[2:])
+    address = output_key_to_p2tr(taproot_construct(internal_key, [(None, CScript([OP_TRUE]))]).output_pubkey)
     assert_equal(address, 'bcrt1p9yfmy5h72durp7zrhlw9lf7jpwjgvwdg0jr0lqmmjtgg83266lqsekaqka')
     return (address, internal_key)
 
@@ -141,6 +140,10 @@ def script_to_p2sh_p2wsh(script, main=False):
     p2shscript = CScript([OP_0, sha256(script)])
     return script_to_p2sh(p2shscript, main)
 
+def output_key_to_p2tr(key, main=False):
+    assert len(key) == 32
+    return program_to_witness(1, key, main)
+
 def check_key(key):
     if (type(key) is str):
         key = bytes.fromhex(key)  # Assuming this is hex string

test/functional/test_framework/script_util.py

@@ -105,6 +105,11 @@ def script_to_p2sh_p2wsh_script(script):
     return script_to_p2sh_script(p2shscript)
 
 
+def output_key_to_p2tr_script(key):
+    assert len(key) == 32
+    return program_to_witness_script(1, key)
+
+
 def check_key(key):
     if isinstance(key, str):
         key = bytes.fromhex(key)  # Assuming this is hex string

test/functional/test_framework/wallet.py

@@ -19,9 +19,13 @@ from test_framework.address import (
     key_to_p2pkh,
     key_to_p2sh_p2wpkh,
     key_to_p2wpkh,
+    output_key_to_p2tr,
 )
 from test_framework.descriptors import descsum_create
-from test_framework.key import ECKey
+from test_framework.key import (
+    ECKey,
+    compute_xonly_pubkey,
+)
 from test_framework.messages import (
     COIN,
     COutPoint,
@@ -38,6 +42,7 @@ from test_framework.script import (
     OP_NOP,
     OP_TRUE,
     SIGHASH_ALL,
+    taproot_construct,
 )
 from test_framework.script_util import (
     key_to_p2pk_script,
@@ -286,10 +291,10 @@ class MiniWallet:
         return txid
 
 
-def getnewdestination(address_type='bech32'):
+def getnewdestination(address_type='bech32m'):
     """Generate a random destination of the specified type and return the
        corresponding public key, scriptPubKey and address. Supported types are
-       'legacy', 'p2sh-segwit' and 'bech32'. Can be used when a random
+       'legacy', 'p2sh-segwit', 'bech32' and 'bech32m'. Can be used when a random
        destination is needed, but no compiled wallet is available (e.g. as
        replacement to the getnewaddress/getaddressinfo RPCs)."""
     key = ECKey()
@@ -304,7 +309,11 @@ def getnewdestination(address_type='bech32'):
     elif address_type == 'bech32':
         scriptpubkey = key_to_p2wpkh_script(pubkey)
         address = key_to_p2wpkh(pubkey)
-    # TODO: also support bech32m (need to generate x-only-pubkey)
+    elif address_type == 'bech32m':
+        tap = taproot_construct(compute_xonly_pubkey(key.get_bytes())[0])
+        pubkey = tap.output_pubkey
+        scriptpubkey = tap.scriptPubKey
+        address = output_key_to_p2tr(pubkey)
     else:
         assert False
     return pubkey, scriptpubkey, address