refactor: make assert_tx_failed a contextmanager (vyperlang#3706)

rename `assert_tx_failed` to `tx_failed` and change it into a context
manager which has a similar API to `pytest.raises()`.

---------

Co-authored-by: Charles Cooper <cooper.charles.m@gmail.com>

docs/testing-contracts-ethtester.rst

@@ -55,9 +55,9 @@ To test events and failed transactions we expand our simple storage contract to
 
 Next, we take a look at the two fixtures that will allow us to read the event logs and to check for failed transactions.
 
-.. literalinclude:: ../tests/base_conftest.py
+.. literalinclude:: ../tests/conftest.py
     :language: python
-    :pyobject: assert_tx_failed
+    :pyobject: tx_failed
 
 The fixture to assert failed transactions defaults to check for a ``TransactionFailed`` exception, but can be used to check for different exceptions too, as shown below. Also note that the chain gets reverted to the state before the failed transaction.
 

tests/conftest.py

@@ -1,5 +1,6 @@
 import json
 import logging
+from contextlib import contextmanager
 from functools import wraps
 
 import hypothesis
@@ -411,23 +412,6 @@ def assert_compile_failed(function_to_test, exception=Exception):
     return assert_compile_failed
 
 
-# TODO this should not be a fixture
-@pytest.fixture
-def search_for_sublist():
-    def search_for_sublist(ir, sublist):
-        _list = ir.to_list() if hasattr(ir, "to_list") else ir
-        if _list == sublist:
-            return True
-        if isinstance(_list, list):
-            for i in _list:
-                ret = search_for_sublist(i, sublist)
-                if ret is True:
-                    return ret
-        return False
-
-    return search_for_sublist
-
-
 @pytest.fixture
 def create2_address_of(keccak):
     def _f(_addr, _salt, _initcode):
@@ -484,16 +468,16 @@ def get_logs(tx_hash, c, event_name):
     return get_logs
 
 
-# TODO replace me with function like `with anchor_state()`
 @pytest.fixture(scope="module")
-def assert_tx_failed(tester):
-    def assert_tx_failed(function_to_test, exception=TransactionFailed, exc_text=None):
+def tx_failed(tester):
+    @contextmanager
+    def fn(exception=TransactionFailed, exc_text=None):
         snapshot_id = tester.take_snapshot()
         with pytest.raises(exception) as excinfo:
-            function_to_test()
+            yield excinfo
         tester.revert_to_snapshot(snapshot_id)
         if exc_text:
             # TODO test equality
             assert exc_text in str(excinfo.value), (exc_text, excinfo.value)
 
-    return assert_tx_failed
+    return fn

tests/functional/builtins/codegen/test_abi_decode.py

@@ -331,7 +331,7 @@ def abi_decode(x: Bytes[32]) -> uint256:
         b"\x01" * 96,  # Length of byte array is beyond size bound of output type
     ],
 )
-def test_clamper(get_contract, assert_tx_failed, input_):
+def test_clamper(get_contract, tx_failed, input_):
     contract = """
 @external
 def abi_decode(x: Bytes[96]) -> (uint256, uint256):
@@ -341,10 +341,11 @@ def abi_decode(x: Bytes[96]) -> (uint256, uint256):
     return a, b
     """
     c = get_contract(contract)
-    assert_tx_failed(lambda: c.abi_decode(input_))
+    with tx_failed():
+        c.abi_decode(input_)
 
 
-def test_clamper_nested_uint8(get_contract, assert_tx_failed):
+def test_clamper_nested_uint8(get_contract, tx_failed):
     # check that _abi_decode clamps on word-types even when it is in a nested expression
     # decode -> validate uint8 -> revert if input >= 256 -> cast back to uint256
     contract = """
@@ -355,10 +356,11 @@ def abi_decode(x: uint256) -> uint256:
     """
     c = get_contract(contract)
     assert c.abi_decode(255) == 255
-    assert_tx_failed(lambda: c.abi_decode(256))
+    with tx_failed():
+        c.abi_decode(256)
 
 
-def test_clamper_nested_bytes(get_contract, assert_tx_failed):
+def test_clamper_nested_bytes(get_contract, tx_failed):
     # check that _abi_decode clamps dynamic even when it is in a nested expression
     # decode -> validate Bytes[20] -> revert if len(input) > 20 -> convert back to -> add 1
     contract = """
@@ -369,7 +371,8 @@ def abi_decode(x: Bytes[96]) -> Bytes[21]:
     """
     c = get_contract(contract)
     assert c.abi_decode(abi.encode("(bytes)", (b"bc",))) == b"abc"
-    assert_tx_failed(lambda: c.abi_decode(abi.encode("(bytes)", (b"a" * 22,))))
+    with tx_failed():
+        c.abi_decode(abi.encode("(bytes)", (b"a" * 22,)))
 
 
 @pytest.mark.parametrize(
@@ -381,7 +384,7 @@ def abi_decode(x: Bytes[96]) -> Bytes[21]:
         ("Bytes[5]", b"\x01" * 192),
     ],
 )
-def test_clamper_dynamic(get_contract, assert_tx_failed, output_typ, input_):
+def test_clamper_dynamic(get_contract, tx_failed, output_typ, input_):
     contract = f"""
 @external
 def abi_decode(x: Bytes[192]) -> {output_typ}:
@@ -390,7 +393,8 @@ def abi_decode(x: Bytes[192]) -> {output_typ}:
     return a
     """
     c = get_contract(contract)
-    assert_tx_failed(lambda: c.abi_decode(input_))
+    with tx_failed():
+        c.abi_decode(input_)
 
 
 @pytest.mark.parametrize(
@@ -422,7 +426,7 @@ def abi_decode(x: Bytes[160]) -> uint256:
         ("Bytes[5]", "address", b"\x01" * 128),
     ],
 )
-def test_clamper_dynamic_tuple(get_contract, assert_tx_failed, output_typ1, output_typ2, input_):
+def test_clamper_dynamic_tuple(get_contract, tx_failed, output_typ1, output_typ2, input_):
     contract = f"""
 @external
 def abi_decode(x: Bytes[224]) -> ({output_typ1}, {output_typ2}):
@@ -432,7 +436,8 @@ def abi_decode(x: Bytes[224]) -> ({output_typ1}, {output_typ2}):
     return a, b
     """
     c = get_contract(contract)
-    assert_tx_failed(lambda: c.abi_decode(input_))
+    with tx_failed():
+        c.abi_decode(input_)
 
 
 FAIL_LIST = [

tests/functional/builtins/codegen/test_addmod.py

@@ -1,4 +1,4 @@
-def test_uint256_addmod(assert_tx_failed, get_contract_with_gas_estimation):
+def test_uint256_addmod(tx_failed, get_contract_with_gas_estimation):
     uint256_code = """
 @external
 def _uint256_addmod(x: uint256, y: uint256, z: uint256) -> uint256:
@@ -11,7 +11,8 @@ def _uint256_addmod(x: uint256, y: uint256, z: uint256) -> uint256:
     assert c._uint256_addmod(32, 2, 32) == 2
     assert c._uint256_addmod((2**256) - 1, 0, 2) == 1
     assert c._uint256_addmod(2**255, 2**255, 6) == 4
-    assert_tx_failed(lambda: c._uint256_addmod(1, 2, 0))
+    with tx_failed():
+        c._uint256_addmod(1, 2, 0)
 
 
 def test_uint256_addmod_ext_call(

tests/functional/builtins/codegen/test_as_wei_value.py

@@ -23,7 +23,7 @@
 
 
 @pytest.mark.parametrize("denom,multiplier", wei_denoms.items())
-def test_wei_uint256(get_contract, assert_tx_failed, denom, multiplier):
+def test_wei_uint256(get_contract, tx_failed, denom, multiplier):
     code = f"""
 @external
 def foo(a: uint256) -> uint256:
@@ -36,11 +36,12 @@ def foo(a: uint256) -> uint256:
     assert c.foo(value) == value * (10**multiplier)
 
     value = (2**256 - 1) // (10 ** (multiplier - 1))
-    assert_tx_failed(lambda: c.foo(value))
+    with tx_failed():
+        c.foo(value)
 
 
 @pytest.mark.parametrize("denom,multiplier", wei_denoms.items())
-def test_wei_int128(get_contract, assert_tx_failed, denom, multiplier):
+def test_wei_int128(get_contract, tx_failed, denom, multiplier):
     code = f"""
 @external
 def foo(a: int128) -> uint256:
@@ -54,7 +55,7 @@ def foo(a: int128) -> uint256:
 
 
 @pytest.mark.parametrize("denom,multiplier", wei_denoms.items())
-def test_wei_decimal(get_contract, assert_tx_failed, denom, multiplier):
+def test_wei_decimal(get_contract, tx_failed, denom, multiplier):
     code = f"""
 @external
 def foo(a: decimal) -> uint256:
@@ -69,20 +70,21 @@ def foo(a: decimal) -> uint256:
 
 @pytest.mark.parametrize("value", (-1, -(2**127)))
 @pytest.mark.parametrize("data_type", ["decimal", "int128"])
-def test_negative_value_reverts(get_contract, assert_tx_failed, value, data_type):
+def test_negative_value_reverts(get_contract, tx_failed, value, data_type):
     code = f"""
 @external
 def foo(a: {data_type}) -> uint256:
     return as_wei_value(a, "ether")
     """
 
     c = get_contract(code)
-    assert_tx_failed(lambda: c.foo(value))
+    with tx_failed():
+        c.foo(value)
 
 
 @pytest.mark.parametrize("denom,multiplier", wei_denoms.items())
 @pytest.mark.parametrize("data_type", ["decimal", "int128", "uint256"])
-def test_zero_value(get_contract, assert_tx_failed, denom, multiplier, data_type):
+def test_zero_value(get_contract, tx_failed, denom, multiplier, data_type):
     code = f"""
 @external
 def foo(a: {data_type}) -> uint256:

tests/functional/builtins/codegen/test_convert.py

@@ -511,7 +511,7 @@ def bar(a: uint256) -> Roles:
 @pytest.mark.parametrize("typ", ["uint8", "int128", "int256", "uint256"])
 @pytest.mark.parametrize("val", [1, 2, 3, 4, 2**128, 2**256 - 1, 2**256 - 2])
 def test_flag_conversion_2(
-    get_contract_with_gas_estimation, assert_compile_failed, assert_tx_failed, val, typ
+    get_contract_with_gas_estimation, assert_compile_failed, tx_failed, val, typ
 ):
     contract = f"""
 flag Status:
@@ -529,7 +529,8 @@ def foo(a: {typ}) -> Status:
         if lo <= val <= hi:
             assert c.foo(val) == val
         else:
-            assert_tx_failed(lambda: c.foo(val))
+            with tx_failed():
+                c.foo(val)
     else:
         assert_compile_failed(lambda: get_contract_with_gas_estimation(contract), TypeMismatch)
 
@@ -608,7 +609,7 @@ def foo() -> {t_bytes}:
 @pytest.mark.parametrize("i_typ,o_typ,val", generate_reverting_cases())
 @pytest.mark.fuzzing
 def test_conversion_failures(
-    get_contract_with_gas_estimation, assert_compile_failed, assert_tx_failed, i_typ, o_typ, val
+    get_contract_with_gas_estimation, assert_compile_failed, tx_failed, i_typ, o_typ, val
 ):
     """
     Test multiple contracts and check for a specific exception.
@@ -650,7 +651,8 @@ def foo():
     """
 
     c2 = get_contract_with_gas_estimation(contract_2)
-    assert_tx_failed(lambda: c2.foo())
+    with tx_failed():
+        c2.foo()
 
     contract_3 = f"""
 @external
@@ -659,4 +661,5 @@ def foo(bar: {i_typ}) -> {o_typ}:
     """
 
     c3 = get_contract_with_gas_estimation(contract_3)
-    assert_tx_failed(lambda: c3.foo(val))
+    with tx_failed():
+        c3.foo(val)