wallet: return accurate error messages from Coin Selection

and not the general "Insufficient funds" when the wallet
actually have funds.

Two new error messages:

1) If the selection result exceeds the maximum transaction weight,
   we now will return: "The inputs size exceeds the maximum weight".

2) If the user preselected inputs and disallowed the automatic coin
   selection process (no other inputs are allowed), we now will
   return: "The preselected coins total amount does not cover the
   transaction target".

3 files changed, 19 insertions, 11 deletions

diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
index f6a697438a..40ae2fd122 100755
--- a/test/functional/rpc_psbt.py
+++ b/test/functional/rpc_psbt.py
@@ -120,7 +120,9 @@ class PSBTTest(BitcoinTestFramework):
 
         # If inputs are specified, do not automatically add more:
         utxo1 = self.nodes[0].listunspent()[0]
-        assert_raises_rpc_error(-4, "Insufficient funds", self.nodes[0].walletcreatefundedpsbt, [{"txid": utxo1['txid'], "vout": utxo1['vout']}], {self.nodes[2].getnewaddress():90})
+        assert_raises_rpc_error(-4, "The preselected coins total amount does not cover the transaction target. "
+                                    "Please allow other inputs to be automatically selected or include more coins manually",
+                                self.nodes[0].walletcreatefundedpsbt, [{"txid": utxo1['txid'], "vout": utxo1['vout']}], {self.nodes[2].getnewaddress():90})
 
         psbtx1 = self.nodes[0].walletcreatefundedpsbt([{"txid": utxo1['txid'], "vout": utxo1['vout']}], {self.nodes[2].getnewaddress():90}, 0, {"add_inputs": True})['psbt']
         assert_equal(len(self.nodes[0].decodepsbt(psbtx1)['tx']['vin']), 2)
diff --git a/test/functional/wallet_fundrawtransaction.py b/test/functional/wallet_fundrawtransaction.py
index bf218bfee9..8451f45d13 100755
--- a/test/functional/wallet_fundrawtransaction.py
+++ b/test/functional/wallet_fundrawtransaction.py
@@ -27,6 +27,8 @@ from test_framework.util import (
 )
 from test_framework.wallet_util import bytes_to_wif
 
+ERR_NOT_ENOUGH_PRESET_INPUTS = "The preselected coins total amount does not cover the transaction target. " \
+                               "Please allow other inputs to be automatically selected or include more coins manually"
 
 def get_unspent(listunspent, amount):
     for utx in listunspent:
@@ -328,7 +330,7 @@ class RawTransactionsTest(BitcoinTestFramework):
         assert_equal("00", dec_tx['vin'][0]['scriptSig']['hex'])
 
         # Should fail without add_inputs:
-        assert_raises_rpc_error(-4, "Insufficient funds", self.nodes[2].fundrawtransaction, rawtx, {"add_inputs": False})
+        assert_raises_rpc_error(-4, ERR_NOT_ENOUGH_PRESET_INPUTS, self.nodes[2].fundrawtransaction, rawtx, {"add_inputs": False})
         # add_inputs is enabled by default
         rawtxfund = self.nodes[2].fundrawtransaction(rawtx)
 
@@ -360,7 +362,7 @@ class RawTransactionsTest(BitcoinTestFramework):
         assert_equal(utx['txid'], dec_tx['vin'][0]['txid'])
 
         # Should fail without add_inputs:
-        assert_raises_rpc_error(-4, "Insufficient funds", self.nodes[2].fundrawtransaction, rawtx, {"add_inputs": False})
+        assert_raises_rpc_error(-4, ERR_NOT_ENOUGH_PRESET_INPUTS, self.nodes[2].fundrawtransaction, rawtx, {"add_inputs": False})
         rawtxfund = self.nodes[2].fundrawtransaction(rawtx, {"add_inputs": True})
 
         dec_tx  = self.nodes[2].decoderawtransaction(rawtxfund['hex'])
@@ -394,7 +396,7 @@ class RawTransactionsTest(BitcoinTestFramework):
         assert_equal(utx['txid'], dec_tx['vin'][0]['txid'])
 
         # Should fail without add_inputs:
-        assert_raises_rpc_error(-4, "Insufficient funds", self.nodes[2].fundrawtransaction, rawtx, {"add_inputs": False})
+        assert_raises_rpc_error(-4, ERR_NOT_ENOUGH_PRESET_INPUTS, self.nodes[2].fundrawtransaction, rawtx, {"add_inputs": False})
         rawtxfund = self.nodes[2].fundrawtransaction(rawtx, {"add_inputs": True})
 
         dec_tx  = self.nodes[2].decoderawtransaction(rawtxfund['hex'])
@@ -987,7 +989,9 @@ class RawTransactionsTest(BitcoinTestFramework):
             outputs[recipient.getnewaddress()] = 0.1
         wallet.sendmany("", outputs)
         self.generate(self.nodes[0], 10)
-        assert_raises_rpc_error(-4, "Insufficient funds", recipient.fundrawtransaction, rawtx)
+        assert_raises_rpc_error(-4, "The inputs size exceeds the maximum weight. "
+                                    "Please try sending a smaller amount or manually consolidating your wallet's UTXOs",
+                                recipient.fundrawtransaction, rawtx)
         self.nodes[0].unloadwallet("large")
 
     def test_external_inputs(self):
@@ -1128,7 +1132,7 @@ class RawTransactionsTest(BitcoinTestFramework):
                 }
             ]
         }
-        assert_raises_rpc_error(-4, "Insufficient funds", wallet.send, outputs=[{addr1: 8}], options=options)
+        assert_raises_rpc_error(-4, ERR_NOT_ENOUGH_PRESET_INPUTS, wallet.send, outputs=[{addr1: 8}], options=options)
 
         # Case (3), Explicit add_inputs=true and preset inputs (with preset inputs not-covering the target amount)
         options["add_inputs"] = True
@@ -1156,7 +1160,7 @@ class RawTransactionsTest(BitcoinTestFramework):
 
         # 6. Explicit add_inputs=false, no preset inputs:
         options = {"add_inputs": False}
-        assert_raises_rpc_error(-4, "Insufficient funds", wallet.send, outputs=[{addr1: 3}], options=options)
+        assert_raises_rpc_error(-4, ERR_NOT_ENOUGH_PRESET_INPUTS, wallet.send, outputs=[{addr1: 3}], options=options)
 
         ################################################
 
@@ -1173,7 +1177,7 @@ class RawTransactionsTest(BitcoinTestFramework):
             "vout": 1  # change position was hardcoded to index 0
         }]
         outputs = {self.nodes[1].getnewaddress(): 8}
-        assert_raises_rpc_error(-4, "Insufficient funds", wallet.walletcreatefundedpsbt, inputs=inputs, outputs=outputs)
+        assert_raises_rpc_error(-4, ERR_NOT_ENOUGH_PRESET_INPUTS, wallet.walletcreatefundedpsbt, inputs=inputs, outputs=outputs)
 
         # Case (3), Explicit add_inputs=true and preset inputs (with preset inputs not-covering the target amount)
         options["add_inputs"] = True
@@ -1200,7 +1204,7 @@ class RawTransactionsTest(BitcoinTestFramework):
 
         # Case (6). Explicit add_inputs=false, no preset inputs:
         options = {"add_inputs": False}
-        assert_raises_rpc_error(-4, "Insufficient funds", wallet.walletcreatefundedpsbt, inputs=[], outputs=outputs, options=options)
+        assert_raises_rpc_error(-4, ERR_NOT_ENOUGH_PRESET_INPUTS, wallet.walletcreatefundedpsbt, inputs=[], outputs=outputs, options=options)
 
         self.nodes[2].unloadwallet("test_preset_inputs")
 
diff --git a/test/functional/wallet_send.py b/test/functional/wallet_send.py
index eb7d9616a1..ce1de264b2 100755
--- a/test/functional/wallet_send.py
+++ b/test/functional/wallet_send.py
@@ -412,10 +412,12 @@ class WalletSendTest(BitcoinTestFramework):
         assert res["complete"]
         utxo1 = w0.listunspent()[0]
         assert_equal(utxo1["amount"], 50)
+        ERR_NOT_ENOUGH_PRESET_INPUTS = "The preselected coins total amount does not cover the transaction target. " \
+                                       "Please allow other inputs to be automatically selected or include more coins manually"
         self.test_send(from_wallet=w0, to_wallet=w1, amount=51, inputs=[utxo1],
-                       expect_error=(-4, "Insufficient funds"))
+                       expect_error=(-4, ERR_NOT_ENOUGH_PRESET_INPUTS))
         self.test_send(from_wallet=w0, to_wallet=w1, amount=51, inputs=[utxo1], add_inputs=False,
-                       expect_error=(-4, "Insufficient funds"))
+                       expect_error=(-4, ERR_NOT_ENOUGH_PRESET_INPUTS))
         res = self.test_send(from_wallet=w0, to_wallet=w1, amount=51, inputs=[utxo1], add_inputs=True, add_to_wallet=False)
         assert res["complete"]