Add functions to automatically add required signers and validity range (#179)

* Add functions to automatically add required signers and validity range

* Filter out signatures of script hashes

* Fix implementation of last slot no in fixed chain context

* Adjust test cases

* Formatting

* Fix types

* prevent negative validity start

* Update txbuilder to only add signatures and validity when building smart
transactions

* Use all input_addresses instead of actually selected inputs

* Require auto_required_signers to be set to True or None

* Correctly transform to Address

* Use _input_vkey_hashes

* Use _input_vkey_hashes

* Remove input_addresses from tx_builder required signers

* Move signer key hash addition to later

Author: nielstron

pycardano/txbuilder.py

@@ -876,6 +876,9 @@ def build(
         change_address: Optional[Address] = None,
         merge_change: Optional[bool] = False,
         collateral_change_address: Optional[Address] = None,
+        auto_validity_start_offset: Optional[int] = None,
+        auto_ttl_offset: Optional[int] = None,
+        auto_required_signers: Optional[bool] = None,
     ) -> TransactionBody:
         """Build a transaction body from all constraints set through the builder.
 
@@ -885,11 +888,41 @@ def build(
             merge_change (Optional[bool]): If the change address match one of the transaction output, the change amount
                 will be directly added to that transaction output, instead of being added as a separate output.
             collateral_change_address (Optional[Address]): Address to which collateral changes will be returned.
+            auto_validity_start_offset (Optional[int]): Automatically set the validity start interval of the transaction
+                to the current slot number + the given offset (default -1000).
+                A manually set validity start will always take precedence.
+            auto_ttl_offset (Optional[int]): Automatically set the validity end interval (ttl) of the transaction
+                to the current slot number + the given offset (default 10_000).
+                A manually set ttl will always take precedence.
+            auto_required_signers (Optional[bool]): Automatically add all pubkeyhashes of transaction inputs
+                to required signatories (default only for Smart Contract transactions).
+                Manually set required signers will always take precedence.
 
         Returns:
             TransactionBody: A transaction body.
         """
         self._ensure_no_input_exclusion_conflict()
+
+        # only automatically set the validity interval and required signers if scripts are involved
+        is_smart = bool(self.scripts)
+
+        # Automatically set the validity range to a tight value around transaction creation
+        if (
+            is_smart or auto_validity_start_offset is not None
+        ) and self.validity_start is None:
+            last_slot = self.context.last_block_slot
+            # If None is provided, the default value is -1000
+            if auto_validity_start_offset is None:
+                auto_validity_start_offset = -1000
+            self.validity_start = max(0, last_slot + auto_validity_start_offset)
+
+        if (is_smart or auto_ttl_offset is not None) and self.ttl is None:
+            last_slot = self.context.last_block_slot
+            # If None is provided, the default value is 10_000
+            if auto_ttl_offset is None:
+                auto_ttl_offset = 10_000
+            self.ttl = max(0, last_slot + auto_ttl_offset)
+
         selected_utxos = []
         selected_amount = Value()
         for i in self.inputs:
@@ -1021,6 +1054,14 @@ def build(
 
         self.inputs[:] = selected_utxos[:]
 
+        # Automatically set the required signers for smart transactions
+        if (
+            is_smart and auto_required_signers is not False
+        ) and self.required_signers is None:
+            # Collect all signatories from explicitly defined
+            # transaction inputs and collateral inputs, and input addresses
+            self.required_signers = list(self._input_vkey_hashes())
+
         self._set_redeemer_index()
 
         self._set_collateral_return(collateral_change_address or change_address)
@@ -1175,6 +1216,9 @@ def build_and_sign(
         change_address: Optional[Address] = None,
         merge_change: Optional[bool] = False,
         collateral_change_address: Optional[Address] = None,
+        auto_validity_start_offset: Optional[int] = None,
+        auto_ttl_offset: Optional[int] = None,
+        auto_required_signers: Optional[bool] = None,
     ) -> Transaction:
         """Build a transaction body from all constraints set through the builder and sign the transaction with
         provided signing keys.
@@ -1187,6 +1231,15 @@ def build_and_sign(
             merge_change (Optional[bool]): If the change address match one of the transaction output, the change amount
                 will be directly added to that transaction output, instead of being added as a separate output.
             collateral_change_address (Optional[Address]): Address to which collateral changes will be returned.
+            auto_validity_start_offset (Optional[int]): Automatically set the validity start interval of the transaction
+                to the current slot number + the given offset (default -1000).
+                A manually set validity start will always take precedence.
+            auto_ttl_offset (Optional[int]): Automatically set the validity end interval (ttl) of the transaction
+                to the current slot number + the given offset (default 10_000).
+                A manually set ttl will always take precedence.
+            auto_required_signers (Optional[bool]): Automatically add all pubkeyhashes of transaction inputs
+                to required signatories (default only for Smart Contract transactions).
+                Manually set required signers will always take precedence.
 
         Returns:
             Transaction: A signed transaction.
@@ -1196,6 +1249,9 @@ def build_and_sign(
             change_address=change_address,
             merge_change=merge_change,
             collateral_change_address=collateral_change_address,
+            auto_validity_start_offset=auto_validity_start_offset,
+            auto_ttl_offset=auto_ttl_offset,
+            auto_required_signers=auto_required_signers,
         )
         witness_set = self.build_witness_set()
         witness_set.vkey_witnesses = []

test/pycardano/test_txbuilder.py

@@ -178,7 +178,9 @@ def test_tx_builder_raises_utxo_selection(chain_context):
     )
 
     with pytest.raises(UTxOSelectionException) as e:
-        tx_body = tx_builder.build(change_address=sender_address)
+        tx_body = tx_builder.build(
+            change_address=sender_address,
+        )
 
     # The unfulfilled amount includes requested (991000000) and estimated fees (161277)
     assert "Unfulfilled amount:\n {\n  'coin': 991161277" in e.value.args[0]
@@ -301,7 +303,7 @@ def test_tx_builder_mint_multi_asset(chain_context):
 
     tx_builder = TransactionBuilder(chain_context)
     sender = "addr_test1vrm9x2zsux7va6w892g38tvchnzahvcd9tykqf3ygnmwtaqyfg52x"
-    sender_address = Address.from_primitive(sender)
+    sender_address: Address = Address.from_primitive(sender)
 
     # Add sender address as input
     mint = {policy_id.payload: {b"Token1": 1}}
@@ -328,14 +330,16 @@ def test_tx_builder_mint_multi_asset(chain_context):
             [
                 sender_address.to_primitive(),
                 [
-                    5811267,
+                    5809683,
                     {b"1111111111111111111111111111": {b"Token1": 1, b"Token2": 2}},
                 ],
             ],
         ],
-        2: 188733,
+        2: 190317,
         3: 123456789,
+        8: 1000,
         9: mint,
+        14: [sender_address.payment_part.to_primitive()],
     }
 
     assert expected == tx_body.to_primitive()
@@ -806,7 +810,10 @@ def test_build_and_sign(chain_context):
     tx_builder2.add_input_address(sender).add_output(
         TransactionOutput.from_primitive([sender, 500000])
     )
-    tx = tx_builder2.build_and_sign([SK], change_address=sender_address)
+    tx = tx_builder2.build_and_sign(
+        [SK],
+        change_address=sender_address,
+    )
 
     assert tx.transaction_witness_set.vkey_witnesses == [
         VerificationKeyWitness(SK.to_verification_key(), SK.sign(tx_body.hash()))
@@ -981,7 +988,10 @@ def test_tx_builder_no_output(chain_context):
 
     tx_builder.add_input(utxo1)
 
-    tx_body = tx_builder.build(change_address=sender_address, merge_change=True)
+    tx_body = tx_builder.build(
+        change_address=sender_address,
+        merge_change=True,
+    )
 
     expected = {
         0: [[b"11111111111111111111111111111111", 3]],
@@ -1008,7 +1018,10 @@ def test_tx_builder_merge_change_to_output(chain_context):
     tx_builder.add_input(utxo1)
     tx_builder.add_output(TransactionOutput.from_primitive([sender, 10000]))
 
-    tx_body = tx_builder.build(change_address=sender_address, merge_change=True)
+    tx_body = tx_builder.build(
+        change_address=sender_address,
+        merge_change=True,
+    )
 
     expected = {
         0: [[b"11111111111111111111111111111111", 3]],
@@ -1039,7 +1052,10 @@ def test_tx_builder_merge_change_to_output_2(chain_context):
     tx_builder.add_output(TransactionOutput.from_primitive([receiver, 10000]))
     tx_builder.add_output(TransactionOutput.from_primitive([sender, 0]))
 
-    tx_body = tx_builder.build(change_address=sender_address, merge_change=True)
+    tx_body = tx_builder.build(
+        change_address=sender_address,
+        merge_change=True,
+    )
 
     expected = {
         0: [[b"11111111111111111111111111111111", 3]],
@@ -1068,7 +1084,10 @@ def test_tx_builder_merge_change_to_zero_amount_output(chain_context):
     tx_builder.add_input(utxo1)
     tx_builder.add_output(TransactionOutput.from_primitive([sender, 0]))
 
-    tx_body = tx_builder.build(change_address=sender_address, merge_change=True)
+    tx_body = tx_builder.build(
+        change_address=sender_address,
+        merge_change=True,
+    )
 
     expected = {
         0: [[b"11111111111111111111111111111111", 3]],
@@ -1095,7 +1114,10 @@ def test_tx_builder_merge_change_smaller_than_min_utxo(chain_context):
     tx_builder.add_input(utxo1)
     tx_builder.add_output(TransactionOutput.from_primitive([sender, 9800000]))
 
-    tx_body = tx_builder.build(change_address=sender_address, merge_change=True)
+    tx_body = tx_builder.build(
+        change_address=sender_address,
+        merge_change=True,
+    )
 
     expected = {
         0: [[b"11111111111111111111111111111111", 3]],

test/pycardano/util.py

@@ -90,7 +90,7 @@ def epoch(self) -> int:
         return 300
 
     @property
-    def slot(self) -> int:
+    def last_block_slot(self) -> int:
         """Current slot number"""
         return 2000