fix[ux]: remove side effects in compare_type for bytestrings

tests/parser/functions/test_interfaces.py

@@ -696,3 +696,34 @@ def test_call(a: address, b: {type_str}) -> {type_str}:
         code, interface_codes={"jsonabi": {"type": "json", "code": convert_v1_abi(abi)}}
     )
     assert c3.test_call(c1.address, value) == value
+
+
+interface_tuple_return_test_code = """
+@external
+@view
+def test_json(a: {0}) -> (uint256, {0}):
+    return 1, a
+    """
+
+
+@pytest.mark.parametrize("type_str,value", type_str_params)
+def test_json_interface_calls_tuple_return(get_contract, type_str, value):
+    code = interface_tuple_return_test_code.format(type_str)
+
+    abi = compile_code(code, ["abi"])["abi"]
+    c1 = get_contract(code)
+
+    code = f"""
+import jsonabi as jsonabi
+
+@external
+@view
+def test_call(a: address, b: {type_str}) -> (uint256, {type_str}):
+    return jsonabi(a).test_json(b)
+    """
+    c2 = get_contract(code, interface_codes={"jsonabi": {"type": "json", "code": abi}})
+    assert c2.test_call(c1.address, value) == [1, value]
+    c3 = get_contract(
+        code, interface_codes={"jsonabi": {"type": "json", "code": convert_v1_abi(abi)}}
+    )
+    assert c3.test_call(c1.address, value) == [1, value]

vyper/codegen/core.py

@@ -673,6 +673,9 @@ def dummy_node_for_type(typ):
 
 
 def _check_assign_bytes(left, right):
+    if left.typ.maxlen == 0:
+        return
+
     if right.typ.maxlen > left.typ.maxlen:
         raise TypeMismatch(f"Cannot cast from {right.typ} to {left.typ}")  # pragma: notest
 

vyper/semantics/analysis/annotation.py

@@ -5,7 +5,17 @@
     get_exact_type_from_node,
     get_possible_types_from_node,
 )
-from vyper.semantics.types import TYPE_T, EnumT, EventT, SArrayT, StructT, is_type_t
+from vyper.semantics.types import (
+    TYPE_T,
+    BytesT,
+    EnumT,
+    EventT,
+    SArrayT,
+    StringT,
+    StructT,
+    TupleT,
+    is_type_t,
+)
 from vyper.semantics.types.function import ContractFunctionT, MemberFunctionT
 
 
@@ -142,6 +152,11 @@ def visit_Call(self, node, type_):
                 # We should only see special kwargs
                 self.visit(kwarg.value, call_type.call_site_kwargs[kwarg.arg].typ)
 
+            # override return type to handle JSON interfaces with bytestrings
+            # as return types since they are initialized to length `0`
+            ret_typ = call_type.return_type
+                call_type.return_type = type_
+
         elif is_type_t(call_type, EventT):
             # events have no kwargs
             for arg, typ in zip(node.args, list(call_type.typedef.arguments.values())):

vyper/semantics/types/bytestrings.py

@@ -104,20 +104,13 @@ def compare_type(self, other):
         if not super().compare_type(other):
             return False
 
-        # CMC 2022-03-18 TODO this method should be refactored so it does not have side effects
-
-        # when comparing two literals, both now have an equal min-length
+        # comparing two literals
         if not self._length and not other._length:
-            min_length = max(self._min_length, other._min_length)
-            self.set_min_length(min_length)
-            other.set_min_length(min_length)
             return True
 
-        # comparing a defined length to a literal causes the literal to have a fixed length
+        # comparing a defined length to a literal
         if self._length:
-            if not other._length:
-                other.set_length(max(self._length, other._min_length))
-            return self._length >= other._length
+            return self._length >= other._min_length
 
         return other.compare_type(self)