Don't migrate configurations from v4->v6, but instead do v4->v5->v6 to ensure proper changes are enacted.

Migration from v4->v5 missed deprecation of "db_filepath" configuration parameter.
Add tests for configuration migration.

nucypher/config/migrations/__init__.py

@@ -2,7 +2,7 @@ from collections import OrderedDict
 
 from .configuration_v1_to_v2 import configuration_v1_to_v2
 from .configuration_v3_to_v4 import configuration_v3_to_v4
-from .configuration_v4_to_v6 import configuration_v4_to_v6
+from .configuration_v4_to_v5 import configuration_v4_to_v5
 from .configuration_v5_to_v6 import configuration_v5_to_v6
 from .configuration_v6_to_v7 import configuration_v6_to_v7
 
@@ -11,7 +11,7 @@ MIGRATIONS = OrderedDict(
         (1, 2): configuration_v1_to_v2,
         (2, 3): None,  # (no-op)
         (3, 4): configuration_v3_to_v4,
-        (4, 6): configuration_v4_to_v6,
+        (4, 5): configuration_v4_to_v5,
         (5, 6): configuration_v5_to_v6,
         (6, 7): configuration_v6_to_v7,
     }

nucypher/config/migrations/configuration_v4_to_v5.py

@@ -4,8 +4,10 @@ from nucypher.config.migrations.common import perform_migration
 
 
 def __migration(config: Dict) -> Dict:
-    del config["federated_only"]  # deprecated
+    # deprecated
+    del config["federated_only"]
     del config["checksum_address"]
+    del config["db_filepath"]
     return config
 
 

nucypher/config/migrations/configuration_v4_to_v6.py

@@ -1,24 +0,0 @@
-from typing import Dict
-
-from nucypher.blockchain.eth.networks import NetworksInventory
-from nucypher.config.migrations.common import perform_migration
-
-
-def __migration(config: Dict) -> Dict:
-    eth_provider = config["eth_provider_uri"]
-    eth_chain_id = NetworksInventory.get_ethereum_chain_id(config["domain"])
-    polygon_provider = config["payment_provider"]
-    polygon_chain_id = NetworksInventory.get_polygon_chain_id(config["payment_network"])
-    if "condition_provider_uris" in config:
-        return config
-    config["condition_provider_uris"] = {
-        eth_chain_id: [eth_provider],
-        polygon_chain_id: [polygon_provider],
-    }
-    return config
-
-
-def configuration_v4_to_v6(filepath) -> None:
-    perform_migration(
-        old_version=4, new_version=6, migration=__migration, filepath=filepath
-    )

tests/integration/config/data/ursula_v4.json

@@ -0,0 +1,29 @@
+{
+  "federated_only": null,
+  "checksum_address": null,
+  "keystore_path": null,
+  "domain": ":temporary-domain:",
+  "learn_on_same_thread": false,
+  "abort_on_learning_error": false,
+  "start_learning_now": false,
+  "save_metadata": false,
+  "node_storage": {
+    "storage_type": ":memory:"
+  },
+  "lonely": false,
+  "eth_provider_uri": "tester://pyevm",
+  "poa": null,
+  "light": false,
+  "signer_uri": "tester://pyevm",
+  "gas_strategy": "fast",
+  "max_gas_price": null,
+  "operator_address": "0xd45B37d42C0A9e4c6072fcD5A94ee11697275012",
+  "rest_host": "127.0.0.1",
+  "rest_port": 51941,
+  "db_filepath": "/root/.local/share/nucypher/ursula.db",
+  "availability_check": false,
+  "payment_method": "SubscriptionManager",
+  "payment_provider": "tester://pyevm",
+  "payment_network": ":temporary-domain:",
+  "version": 4
+}

tests/integration/config/test_configuration_migrations.py

@@ -0,0 +1,52 @@
+import shutil
+from pathlib import Path
+
+import pytest
+
+import tests
+from nucypher.config.characters import UrsulaConfiguration
+from nucypher.config.migrations import MIGRATIONS
+from nucypher.config.migrations.common import WrongConfigurationVersion
+
+
+def _copy_config_file(src_test_file_name, dst_filepath):
+    src_filepath = (
+        Path(tests.__file__).parent
+        / "integration"
+        / "config"
+        / "data"
+        / src_test_file_name
+    )
+    shutil.copy(src=src_filepath, dst=dst_filepath)
+
+
+def _do_migration(config_file: Path):
+    for jump, migration in MIGRATIONS.items():
+        if not migration:
+            continue  # no migration script
+        try:
+            migration(config_file)
+        except WrongConfigurationVersion:
+            continue
+
+
+@pytest.fixture(scope="function")
+def ursula_v4_config_filepath(tempfile_path):
+    # v4 is the latest public release (from v6.1.0)
+    _copy_config_file("ursula_v4.json", tempfile_path)
+
+    return tempfile_path
+
+
+@pytest.mark.usefixtures("test_registry_source_manager")
+def test_migrate_v4_to_latest(ursula_v4_config_filepath):
+    _do_migration(config_file=ursula_v4_config_filepath)
+
+    # file changed in place
+    migrated_ursula_config_filepath = ursula_v4_config_filepath
+    ursula_config = UrsulaConfiguration.from_configuration_file(
+        migrated_ursula_config_filepath, dev_mode=True
+    )
+
+    # successfully produce an ursula based on latest config
+    _ = ursula_config.produce()