Merge bitcoin/bitcoin#23512: policy: Treat taproot as always active

fa3e0da06b491b8c0fa2dbae37682a9112c9deb8 policy: Treat taproot as always active (MarcoFalke)

Pull request description:

  Now that taproot is active, it can be treated as if it was always active for policy for the next major release. This simplifies the code and changes two things:

  * Importing `tr` descriptors can be done before the chain is fully synced. This is fine, because the wallet will already generate `tr` descriptors by default (regardless of the taproot status) after commit 47fe7445e7f54aee10ec6dbc53f1db1adbeb43de.
  * Valid taproot spends won't be rejected from the mempool before taproot is active. This is strictly speaking a bugfix after commit 47fe7445e7f54aee10ec6dbc53f1db1adbeb43de, since the wallet may generate taproot spends before the chain is fully synced. For example, a slow node or a purposefully offline node. Currently, the wallet needs the mempool to account for change. See https://github.com/bitcoin/bitcoin/issues/11887.

  A similar change was done for segwit v0 in https://github.com/bitcoin/bitcoin/pull/13120 .

  This effectively reverts commit c5ec0367d718544caa3a1578d6c730fc92ee4e94.

ACKs for top commit:
  mjdietzx:
    Code Review ACK fa3e0da06b491b8c0fa2dbae37682a9112c9deb8
  achow101:
    ACK fa3e0da06b491b8c0fa2dbae37682a9112c9deb8
  sipa:
    utACK fa3e0da06b491b8c0fa2dbae37682a9112c9deb8
  gruve-p:
    ACK https://github.com/bitcoin/bitcoin/pull/23512/commits/fa3e0da06b491b8c0fa2dbae37682a9112c9deb8
  gunar:
    Code Review + tACK fa3e0da06
  rajarshimaitra:
    code review + tACK https://github.com/bitcoin/bitcoin/pull/23512/commits/fa3e0da06b491b8c0fa2dbae37682a9112c9deb8

Tree-SHA512: c6dc7a4e6c345bdec33f256847dc63906ab1696aa683ab9b32a79e715613950884ac3a1a7a44e95f31bb28e58dd64679a616175f7e152b21f5550f3337c8e622

2 files changed, 29 insertions, 17 deletions

diff --git a/test/functional/feature_taproot.py b/test/functional/feature_taproot.py
index de679fbf44..e9da6edaf6 100755
--- a/test/functional/feature_taproot.py
+++ b/test/functional/feature_taproot.py
@@ -98,6 +98,7 @@ from test_framework.address import (
     program_to_witness
 )
 from collections import OrderedDict, namedtuple
+from enum import Enum
 from io import BytesIO
 import json
 import hashlib
@@ -456,7 +457,7 @@ def spend(tx, idx, utxos, **kwargs):
 # Each spender is a tuple of:
 # - A scriptPubKey which is to be spent from (CScript)
 # - A comment describing the test (string)
-# - Whether the spending (on itself) is expected to be standard (bool)
+# - Whether the spending (on itself) is expected to be standard (Enum.Standard)
 # - A tx-signing lambda returning (scriptsig, witness_stack), taking as inputs:
 #   - A transaction to sign (CTransaction)
 #   - An input position (int)
@@ -468,8 +469,14 @@ def spend(tx, idx, utxos, **kwargs):
 # - Whether this test demands being placed in a txin with no corresponding txout (for testing SIGHASH_SINGLE behavior)
 
 Spender = namedtuple("Spender", "script,comment,is_standard,sat_function,err_msg,sigops_weight,no_fail,need_vin_vout_mismatch")
+# The full node versions that treat the tx standard.
+# ALL means any version
+# V23 means the major version 23.0 and any later version
+# NONE means no version
+Standard = Enum('Standard', 'ALL V23 NONE')
 
-def make_spender(comment, *, tap=None, witv0=False, script=None, pkh=None, p2sh=False, spk_mutate_pre_p2sh=None, failure=None, standard=True, err_msg=None, sigops_weight=0, need_vin_vout_mismatch=False, **kwargs):
+
+def make_spender(comment, *, tap=None, witv0=False, script=None, pkh=None, p2sh=False, spk_mutate_pre_p2sh=None, failure=None, standard=Standard.ALL, err_msg=None, sigops_weight=0, need_vin_vout_mismatch=False, **kwargs):
     """Helper for constructing Spender objects using the context signing framework.
 
     * tap: a TaprootInfo object (see taproot_construct), for Taproot spends (cannot be combined with pkh, witv0, or script)
@@ -479,13 +486,18 @@ def make_spender(comment, *, tap=None, witv0=False, script=None, pkh=None, p2sh=
     * p2sh: whether the output is P2SH wrapper (this is supported even for Taproot, where it makes the output unencumbered)
     * spk_mutate_pre_psh: a callable to be applied to the script (before potentially P2SH-wrapping it)
     * failure: a dict of entries to override in the context when intentionally failing to spend (if None, no_fail will be set)
-    * standard: whether the (valid version of) spending is expected to be standard
+    * standard: whether the (valid version of) spending is expected to be standard (True is mapped to Standard.ALL, False is mapped to Standard.NONE)
     * err_msg: a string with an expected error message for failure (or None, if not cared about)
     * sigops_weight: the pre-taproot sigops weight consumed by a successful spend
     * need_vin_vout_mismatch: whether this test requires being tested in a transaction input that has no corresponding
                               transaction output.
     """
 
+    if standard == True:
+        standard = Standard.ALL
+    elif standard == False:
+        standard = Standard.NONE
+
     conf = dict()
 
     # Compute scriptPubKey and set useful defaults based on the inputs.
@@ -1170,12 +1182,12 @@ def spenders_taproot_inactive():
     tap = taproot_construct(pub, scripts)
 
     # Test that keypath spending is valid & non-standard, regardless of validity.
-    add_spender(spenders, "inactive/keypath_valid", key=sec, tap=tap, standard=False)
+    add_spender(spenders, "inactive/keypath_valid", key=sec, tap=tap, standard=Standard.V23)
     add_spender(spenders, "inactive/keypath_invalidsig", key=sec, tap=tap, standard=False, sighash=bitflipper(default_sighash))
     add_spender(spenders, "inactive/keypath_empty", key=sec, tap=tap, standard=False, witness=[])
 
     # Same for scriptpath spending (and features like annex, leaf versions, or OP_SUCCESS don't change this)
-    add_spender(spenders, "inactive/scriptpath_valid", key=sec, tap=tap, leaf="pk", standard=False, inputs=[getter("sign")])
+    add_spender(spenders, "inactive/scriptpath_valid", key=sec, tap=tap, leaf="pk", standard=Standard.V23, inputs=[getter("sign")])
     add_spender(spenders, "inactive/scriptpath_invalidsig", key=sec, tap=tap, leaf="pk", standard=False, inputs=[getter("sign")], sighash=bitflipper(default_sighash))
     add_spender(spenders, "inactive/scriptpath_invalidcb", key=sec, tap=tap, leaf="pk", standard=False, inputs=[getter("sign")], controlblock=bitflipper(default_controlblock))
     add_spender(spenders, "inactive/scriptpath_valid_unkleaf", key=sec, tap=tap, leaf="future_leaf", standard=False, inputs=[getter("sign")])
@@ -1205,7 +1217,7 @@ def dump_json_test(tx, input_utxos, idx, success, failure):
 
     # The "final" field indicates that a spend should be always valid, even with more validation flags enabled
     # than the listed ones. Use standardness as a proxy for this (which gives a conservative underestimate).
-    if spender.is_standard:
+    if spender.is_standard == Standard.ALL:
         fields.append(("final", True))
 
     def dump_witness(wit):
@@ -1470,8 +1482,13 @@ class TaprootTest(BitcoinTestFramework):
                 for i in range(len(input_utxos)):
                     tx.vin[i].scriptSig = input_data[i][i != fail_input][0]
                     tx.wit.vtxinwit[i].scriptWitness.stack = input_data[i][i != fail_input][1]
+                taproot_spend_policy = Standard.V23 if node.version is None else Standard.ALL
                 # Submit to mempool to check standardness
-                is_standard_tx = fail_input is None and all(utxo.spender.is_standard for utxo in input_utxos) and tx.nVersion >= 1 and tx.nVersion <= 2
+                is_standard_tx = (
+                    fail_input is None  # Must be valid to be standard
+                    and (all(utxo.spender.is_standard == Standard.ALL or utxo.spender.is_standard == taproot_spend_policy for utxo in input_utxos))  # All inputs must be standard
+                    and tx.nVersion >= 1  # The tx version must be standard
+                    and tx.nVersion <= 2)
                 tx.rehash()
                 msg = ','.join(utxo.spender.comment + ("*" if n == fail_input else "") for n, utxo in enumerate(input_utxos))
                 if is_standard_tx:
diff --git a/test/functional/wallet_taproot.py b/test/functional/wallet_taproot.py
index 614f7e1ec0..17eab25457 100755
--- a/test/functional/wallet_taproot.py
+++ b/test/functional/wallet_taproot.py
@@ -242,20 +242,15 @@ class WalletTaprootTest(BitcoinTestFramework):
             assert_equal(len(rederive), 1)
             assert_equal(rederive[0], addr_g)
 
-        # tr descriptors cannot be imported when Taproot is not active
+        # tr descriptors can be imported regardless of Taproot status
         result = self.privs_tr_enabled.importdescriptors([{"desc": desc, "timestamp": "now"}])
         assert(result[0]["success"])
         result = self.pubs_tr_enabled.importdescriptors([{"desc": desc_pub, "timestamp": "now"}])
         assert(result[0]["success"])
-        if desc.startswith("tr"):
-            result = self.privs_tr_disabled.importdescriptors([{"desc": desc, "timestamp": "now"}])
-            assert(not result[0]["success"])
-            assert_equal(result[0]["error"]["code"], -4)
-            assert_equal(result[0]["error"]["message"], "Cannot import tr() descriptor when Taproot is not active")
-            result = self.pubs_tr_disabled.importdescriptors([{"desc": desc_pub, "timestamp": "now"}])
-            assert(not result[0]["success"])
-            assert_equal(result[0]["error"]["code"], -4)
-            assert_equal(result[0]["error"]["message"], "Cannot import tr() descriptor when Taproot is not active")
+        result = self.privs_tr_disabled.importdescriptors([{"desc": desc, "timestamp": "now"}])
+        assert result[0]["success"]
+        result = self.pubs_tr_disabled.importdescriptors([{"desc": desc_pub, "timestamp": "now"}])
+        assert result[0]["success"]
 
     def do_test_sendtoaddress(self, comment, pattern, privmap, treefn, keys_pay, keys_change):
         self.log.info("Testing %s through sendtoaddress" % comment)