wallet: override minfee checks (fOverrideFeeRate) for fee_rate

in RPCs fundrawtransaction and walletcreatefundedpsbt only.

This provides the existing feeRate (BTC/kvB) behavior in these two RPCs to the
new fee_rate (sat/vB) param also.

See these two GitHub review discussions for more info:
https://github.com/bitcoin/bitcoin/pull/10706/#discussion_r126560525
https://github.com/bitcoin/bitcoin/pull/20305#discussion_r520032533

2 files changed, 10 insertions, 13 deletions

diff --git a/test/functional/rpc_fundrawtransaction.py b/test/functional/rpc_fundrawtransaction.py
index d515b4a7d3..f987867e61 100755
--- a/test/functional/rpc_fundrawtransaction.py
+++ b/test/functional/rpc_fundrawtransaction.py
@@ -752,7 +752,7 @@ class RawTransactionsTest(BitcoinTestFramework):
                     node.fundrawtransaction, rawtx, {"estimate_mode": mode, "conf_target": n, "add_inputs": True})
 
         self.log.info("Test invalid fee rate settings")
-        assert_raises_rpc_error(-4, "Fee rate (0.000 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)",
+        assert_raises_rpc_error(-8, "Invalid fee_rate 0.000 sat/vB (must be greater than 0)",
             node.fundrawtransaction, rawtx, {"fee_rate": 0, "add_inputs": True})
         assert_raises_rpc_error(-8, "Invalid feeRate 0.00000000 BTC/kvB (must be greater than 0)",
             node.fundrawtransaction, rawtx, {"feeRate": 0, "add_inputs": True})
@@ -766,12 +766,9 @@ class RawTransactionsTest(BitcoinTestFramework):
             assert_raises_rpc_error(-3, "Invalid amount",
                 node.fundrawtransaction, rawtx, {"fee_rate": "", "add_inputs": True})
 
-        # Test setting explicit fee rate just below the minimum.
-        self.log.info("- raises RPC error 'fee rate too low' if fee_rate of 0.99999999 sat/vB is passed")
-        msg = "Fee rate (0.999 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)"
-        assert_raises_rpc_error(-4, msg, node.fundrawtransaction, rawtx, {"fee_rate": 0.99999999, "add_inputs": True})
-        # This feeRate test only passes if `coinControl.fOverrideFeeRate = true` in wallet/rpcwallet.cpp::FundTransaction is removed.
-        # assert_raises_rpc_error(-4, msg, node.fundrawtransaction, rawtx, {"feeRate": 0.00000999, "add_inputs": True})
+        self.log.info("Test min fee rate checks are bypassed with fundrawtxn, e.g. a fee_rate under 1 sat/vB is allowed")
+        node.fundrawtransaction(rawtx, {"fee_rate": 0.99999999, "add_inputs": True})
+        node.fundrawtransaction(rawtx, {"feeRate": 0.00000999, "add_inputs": True})
 
         self.log.info("- raises RPC error if both feeRate and fee_rate are passed")
         assert_raises_rpc_error(-8, "Cannot specify both fee_rate (sat/vB) and feeRate (BTC/kvB)",
diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
index 313611ca17..498197b5e5 100755
--- a/test/functional/rpc_psbt.py
+++ b/test/functional/rpc_psbt.py
@@ -192,9 +192,14 @@ class PSBTTest(BitcoinTestFramework):
         assert_approx(res1["fee"], 0.055, 0.005)
         res2 = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"feeRate": 0.1, "add_inputs": True})
         assert_approx(res2["fee"], 0.055, 0.005)
+        self.log.info("Test min fee rate checks with walletcreatefundedpsbt are bypassed, e.g. a fee_rate under 1 sat/vB is allowed")
+        res3 = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"fee_rate": 0.99999999, "add_inputs": True})
+        assert_approx(res3["fee"], 0.00000381, 0.0000001)
+        res4 = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"feeRate": 0.00000999, "add_inputs": True})
+        assert_approx(res4["fee"], 0.00000381, 0.0000001)
 
         self.log.info("Test invalid fee rate settings")
-        assert_raises_rpc_error(-4, "Fee rate (0.000 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)",
+        assert_raises_rpc_error(-8, "Invalid fee_rate 0.000 sat/vB (must be greater than 0)",
             self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"fee_rate": 0, "add_inputs": True})
         assert_raises_rpc_error(-8, "Invalid feeRate 0.00000000 BTC/kvB (must be greater than 0)",
             self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"feeRate": 0, "add_inputs": True})
@@ -244,11 +249,6 @@ class PSBTTest(BitcoinTestFramework):
                 assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",  # max value of 1008 per src/policy/fees.h
                     self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"estimate_mode": mode, "conf_target": n, "add_inputs": True})
 
-        # Test setting explicit fee rate just below the minimum.
-        self.log.info("- raises RPC error 'fee rate too low' if feerate_sat_vb of 0.99999999 is passed")
-        assert_raises_rpc_error(-4, "Fee rate (0.999 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)",
-            self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"fee_rate": 0.99999999, "add_inputs": True})
-
         self.log.info("Test walletcreatefundedpsbt with too-high fee rate produces total fee well above -maxtxfee and raises RPC error")
         # previously this was silently capped at -maxtxfee
         for bool_add, outputs_array in {True: outputs, False: [{self.nodes[1].getnewaddress(): 1}]}.items():