Fixed issue with ethereum provider not looking at subscriptions

Before, the `ethereum_blockchain` provider was returning all blockchain
transactions in the given stream boundary.

Now, it only returns transactions that are relevant to the user's
subscriptions.

backend/moonstream/providers/ethereum_blockchain.py

@@ -73,15 +73,18 @@ class Filters:
     to_addresses: List[str] = field(default_factory=list)
 
 
-def default_filters(subscriptions: List[BugoutResource]) -> List[str]:
+def default_filters(subscriptions: List[BugoutResource]) -> Filters:
     """
     Default filter strings for the given list of subscriptions.
     """
-    filters = []
+    filters = Filters()
     for subscription in subscriptions:
-        subscription_address = subscription.resource_data.get("address")
+        subscription_address = cast(
+            Optional[str], subscription.resource_data.get("address")
+        )
         if subscription_address is not None:
-            filters.append(cast(str, subscription_address))
+            filters.from_addresses.append(subscription_address)
+            filters.to_addresses.append(subscription_address)
         else:
             logger.warn(
                 f"Could not find subscription address for subscription with resource id: {subscription.id}"
@@ -104,10 +107,20 @@ def parse_filters(
     If the given StreamQuery induces filters on this provider, returns those filters. Otherwise, returns
     None indicating that the StreamQuery does not require any data from this provider.
     """
+    if query.subscription_types and not any(
+        subtype == event_type for subtype in query.subscription_types
+    ):
+        return None
+
     provider_subscriptions = user_subscriptions.get(event_type)
+
     # If the user has no subscriptions to this event type, we do not have to return any data!
     if not provider_subscriptions:
         return None
+    parsed_filters = default_filters(provider_subscriptions)
+
+    from_prefix_length = len("from:")
+    to_prefix_length = len("to:")
 
     subscribed_addresses = {
         subscription.resource_data.get("address")
@@ -115,38 +128,28 @@ def parse_filters(
         if subscription.resource_data.get("address") is not None
     }
 
-    requires_ethereum_blockchain_data = False
+    if query.subscriptions:
-    for subtype in query.subscription_types:
+        parsed_filters.from_addresses = []
-        if subtype == event_type:
+        parsed_filters.to_addresses = []
-            requires_ethereum_blockchain_data = True
+        for provider_type, raw_filter in query.subscriptions:
+            if provider_type != event_type:
+                continue
 
-    parsed_filters = Filters()
+            if raw_filter.startswith("from:"):
+                address = raw_filter[from_prefix_length:]
+                if address in subscribed_addresses:
+                    parsed_filters.from_addresses.append(address)
+            elif raw_filter.startswith("to:"):
+                address = raw_filter[to_prefix_length:]
+                if address in subscribed_addresses:
+                    parsed_filters.to_addresses.append(address)
+            else:
+                address = raw_filter
+                if address in subscribed_addresses:
+                    parsed_filters.from_addresses.append(address)
+                    parsed_filters.to_addresses.append(address)
 
-    from_slice_start = len("from:")
+    if not (parsed_filters.from_addresses or parsed_filters.to_addresses):
-    to_slice_start = len("to:")
-
-    for provider_type, raw_filter in query.subscriptions:
-        if provider_type != event_type:
-            continue
-
-        if raw_filter.startswith("from:"):
-            address = raw_filter[from_slice_start:]
-            if address in subscribed_addresses:
-                parsed_filters.from_addresses.append(address)
-        elif raw_filter.startswith("to:"):
-            address = raw_filter[to_slice_start:]
-            if address in subscribed_addresses:
-                parsed_filters.to_addresses.append(address)
-        else:
-            address = raw_filter
-            if address in subscribed_addresses:
-                parsed_filters.from_addresses.append(address)
-                parsed_filters.to_addresses.append(address)
-
-    if parsed_filters.from_addresses or parsed_filters.to_addresses:
-        requires_ethereum_blockchain_data = True
-
-    if not requires_ethereum_blockchain_data:
         return None
 
     return parsed_filters