eth: unknown token transfer is recognized and displayed as unknown

updates #198

src/apps/ethereum/layout.py

@@ -1,4 +1,5 @@
 from apps.common.confirm import *
+from apps.ethereum import tokens
 from trezor import ui
 from trezor.utils import chunks, format_amount
 from trezor.messages import ButtonRequestType
@@ -53,6 +54,8 @@ def split_address(address):
 
 def format_ethereum_amount(value: int, token, chain_id: int, tx_type=None):
     if token:
+        if token is tokens.UNKNOWN_TOKEN:
+            return 'Unknown token value'
         suffix = token[2]
         decimals = token[3]
     else:

src/apps/ethereum/tokens.py

@@ -1,12 +1,12 @@
 def token_by_chain_address(chain_id, address):
-    if not address:
-        return None
     for token in tokens:
         if chain_id == token[0] and address == token[1]:
             return token
-    return None
+    return UNKNOWN_TOKEN
 
 
+UNKNOWN_TOKEN = True
+
 # rest of the file is generated using trezor-common/ethereum_tokens-gen.py
 # DO NOT EDIT MANUALLY!
 tokens = [

tests/test_apps.ethereum.tokens.py

@@ -22,7 +22,7 @@ class TestEthereumTokens(unittest.TestCase):
 
         # invalid adress, invalid chain
         token = tokens.token_by_chain_address(999, b'\x00\xFF')
-        self.assertEqual(token, None)
+        self.assertEqual(token, tokens.UNKNOWN_TOKEN)
 
 
 if __name__ == '__main__':