[EXP-14-216] fix: oracle regression

yearn/exceptions.py

@@ -8,3 +8,7 @@ class PriceError(Exception):
 
 class ArchiveNodeRequired(Exception):
     pass
+
+
+class MulticallError(Exception):
+    pass

yearn/multicall2.py

@@ -8,6 +8,7 @@
 
 from yearn.networks import Network
 from yearn.utils import contract_creation_block, contract
+from yearn.exceptions import MulticallError
 
 MULTICALL2 = {
     Network.Mainnet: '0x5BA1e12693Dc8F9c48aAD8770482f4739bEeD696',
@@ -17,7 +18,7 @@
 multicall2 = contract(MULTICALL2[chain.id])
 
 
-def fetch_multicall(*calls, block=None):
+def fetch_multicall(*calls, block=None, require_success=False):
     # https://github.com/makerdao/multicall
     multicall_input = []
     fn_list = []
@@ -52,6 +53,8 @@ def fetch_multicall(*calls, block=None):
             assert ok, "call failed"
             decoded.append(fn.decode_output(data))
         except (AssertionError, InsufficientDataBytes):
+            if require_success:
+                raise MulticallError()
             decoded.append(None)
 
     return decoded

yearn/outputs/describers/vault.py

@@ -39,7 +39,10 @@ def _get_price(token_address, block=None):
             # https://github.com/yearn/yearn-security/blob/master/disclosures/2021-05-13.md
             if token_address == '0x03403154afc09Ce8e44C3B185C82C6aD5f86b9ab' and 12430455 <= block <= 12430661:
                 return 1.091553
+            # GUSD vault state was broken due to an incident, return a post-fix price
+            # https://github.com/yearn/yearn-security/blob/master/disclosures/2021-01-17.md
+            elif token_address == '0x03403154afc09Ce8e44C3B185C82C6aD5f86b9ab' and 11603873 <= block <= 11645877:
+                return 0
 
         logger.exception(e)
-
-    return 0
+        raise e

yearn/prices/yearn.py

@@ -2,7 +2,7 @@
 from yearn.networks import Network
 from yearn.utils import Singleton, contract
 from brownie import chain
-from yearn.exceptions import UnsupportedNetwork
+from yearn.exceptions import MulticallError, UnsupportedNetwork
 import logging
 from cachetools.func import ttl_cache
 
@@ -60,23 +60,34 @@ def is_yearn_vault(self, token):
         )
 
     def get_price(self, token, block=None):
-        # v1 vaults use getPricePerFullShare scaled to 18 decimals
         # v2 vaults use pricePerShare scaled to underlying token decimals
         vault = contract(token)
         if hasattr(vault, 'pricePerShare'):
-            share_price, underlying, decimals = fetch_multicall(
-                [vault, 'pricePerShare'],
-                [vault, 'token'],
-                [vault, 'decimals'],
-                block=block,
-            )
-            if share_price and underlying and decimals:
+            try:
+                share_price, underlying, decimals = fetch_multicall(
+                    [vault, 'pricePerShare'],
+                    [vault, 'token'],
+                    [vault, 'decimals'],
+                    block=block,
+                    require_success=True,
+                )
+            except MulticallError:
+                return None
+            else:
                 return [share_price / 10 ** decimals, underlying]
+
+        # v1 vaults use getPricePerFullShare scaled to 18 decimals
         if hasattr(vault, 'getPricePerFullShare'):
-            share_price, underlying = fetch_multicall(
-                [vault, 'getPricePerFullShare'], [vault, 'token'], block=block
-            )
-            if share_price and underlying:
+            try:
+                share_price, underlying = fetch_multicall(
+                    [vault, 'getPricePerFullShare'],
+                    [vault, 'token'],
+                    block=block,
+                    require_success=True,
+                )
+            except MulticallError:
+                return None
+            else:
                 return [share_price / 1e18, underlying]