Contract call optimization - remove round trip

tests/core/contracts/test_contract_call_interface.py

@@ -391,9 +391,6 @@ def test_call_fallback_function(fallback_function_contract):
 
 def test_throws_error_if_block_out_of_range(web3, math_contract):
     web3.providers[0].make_request(method='evm_mine', params=[20])
-    with pytest.raises(BlockNumberOutofRange):
-        math_contract.functions.counter().call(block_identifier=50)
-
     with pytest.raises(BlockNumberOutofRange):
         math_contract.functions.counter().call(block_identifier=-50)
 

tests/core/contracts/test_contract_util_functions.py

@@ -0,0 +1,13 @@
+from web3.contract import (
+    parse_block_identifier_int,
+)
+
+
+#  This tests negative block number identifiers, which behave like python
+#  list slices, with -1 being the latest block and -2 being the block before that.
+#  This test is necessary because transaction calls allow negative block indexes, although
+#  getBlock() does not allow negative block identifiers. Support for negative block identifier
+#  will likely be removed in v5.
+def test_parse_block_identifier_int(web3):
+    last_num = web3.eth.getBlock('latest').number
+    assert 0 == parse_block_identifier_int(web3, -1 - last_num)

web3/contract.py

@@ -1397,12 +1397,8 @@ def call_contract_function(
 
 
 def parse_block_identifier(web3, block_identifier):
-    last_block = web3.eth.getBlock('latest').number
-    if isinstance(block_identifier, int) and abs(block_identifier) <= last_block:
-        if block_identifier >= 0:
-            return block_identifier
-        else:
-            return last_block + block_identifier + 1
+    if isinstance(block_identifier, int):
+        return parse_block_identifier_int(web3, block_identifier)
     elif block_identifier in ['latest', 'earliest', 'pending']:
         return block_identifier
     elif isinstance(block_identifier, bytes) or is_hex_encoded_block_hash(block_identifier):
@@ -1411,6 +1407,17 @@ def parse_block_identifier(web3, block_identifier):
         raise BlockNumberOutofRange
 
 
+def parse_block_identifier_int(web3, block_identifier_int):
+    if block_identifier_int >= 0:
+        block_num = block_identifier_int
+    else:
+        last_block = web3.eth.getBlock('latest').number
+        block_num = last_block + block_identifier_int + 1
+        if block_num < 0:
+            raise BlockNumberOutofRange
+    return block_num
+
+
 def transact_with_contract_function(
         address,
         web3,