fix: resolve all ruff lint errors (54 issues)

- B904: add `from None`/`from err` to re-raises in except clauses
- B008: suppress for FastAPI Depends() pattern (standard usage)
- B905: add strict= to zip() calls
- B007: rename unused loop vars to _
- SIM102/SIM108/SIM110: simplify conditionals and ternaries
- F841: remove unused variable assignments
- F811: deduplicate conftest fixtures (remove MockBpfMap-based
  versions superseded by MagicMock-based versions)
- E402: move mid-file imports to top in conftest files
- N818: rename exception to end with Error

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Alexander Martynenko

pyproject.toml

@@ -61,7 +61,7 @@ target-version = "py312"
 
 [tool.ruff.lint]
 select = ["E", "F", "W", "I", "N", "B", "C4", "SIM"]
-ignore = ["E501"]
+ignore = ["E501", "B008"]
 
 [tool.mypy]
 python_version = "3.12"

src/katran/api/rest/app.py

@@ -85,7 +85,7 @@ def _parse_protocol(proto_str: str) -> Protocol:
     try:
         return Protocol[proto_str.upper()]
     except KeyError:
-        raise HTTPException(status_code=400, detail=f"Invalid protocol: {proto_str}")
+        raise HTTPException(status_code=400, detail=f"Invalid protocol: {proto_str}") from None
 
 
 def _vip_to_response(vip: Any) -> VipResponse:

src/katran/bpf/maps/ch_rings_map.py

@@ -162,7 +162,7 @@ def write_ring(
         old_ring = self.read_ring(vip_num)
         updates = {}
 
-        for i, (old_val, new_val) in enumerate(zip(old_ring, ring)):
+        for i, (old_val, new_val) in enumerate(zip(old_ring, ring, strict=False)):
             if old_val != new_val:
                 updates[i] = new_val
 
@@ -288,7 +288,7 @@ def write_ring_incremental(
 
         # Compute positions that changed
         updates = {}
-        for i, (old_val, new_val) in enumerate(zip(old_ring, new_ring)):
+        for i, (old_val, new_val) in enumerate(zip(old_ring, new_ring, strict=False)):
             if old_val != new_val:
                 updates[i] = new_val
 

src/katran/bpf/maps/lru_map.py

@@ -188,7 +188,7 @@ def get_cache_stats(self) -> dict[str, int]:
         backend_counts: dict[int, int] = {}
         total = 0
 
-        for flow, cached in self.items():
+        for _flow, cached in self.items():
             total += 1
             backend_counts[cached.pos] = backend_counts.get(cached.pos, 0) + 1
 

src/katran/bpf/maps/reals_map.py

@@ -239,9 +239,7 @@ def sync_from_map(self) -> None:
 
             for i in range(1, self._max_reals):
                 real_def = self.get(i)
-                if real_def is not None:
-                    # Check if entry is non-zero (has valid address)
-                    if real_def.address.packed != b"\x00" * 4:
+                if real_def is not None and real_def.address.packed != b"\x00" * 4:
                         self._reals_cache[i] = real_def
                         self._index_allocator.reserve(i)
 

src/katran/core/config.py

@@ -169,9 +169,7 @@ def _is_flat_config(data: dict[str, Any]) -> bool:
     if set(data.keys()) & unambiguous_flat:
         return True
     # "interface" exists in both formats: str in flat, dict in nested
-    if "interface" in data and isinstance(data["interface"], str):
-        return True
-    return False
+    return bool("interface" in data and isinstance(data["interface"], str))
 
 
 def _normalize_flat_config(data: dict[str, Any]) -> dict[str, Any]:
@@ -229,25 +227,25 @@ def from_yaml(cls, path: str | Path) -> KatranConfig:
             with open(path) as f:
                 data = yaml.safe_load(f)
         except FileNotFoundError:
-            raise ConfigurationError(f"Config file not found: {path}")
+            raise ConfigurationError(f"Config file not found: {path}") from None
         except yaml.YAMLError as e:
-            raise ConfigurationError(f"Invalid YAML: {e}")
+            raise ConfigurationError(f"Invalid YAML: {e}") from e
 
         if data is None:
             data = {}
 
         try:
             return cls.model_validate(data)
         except Exception as e:
-            raise ConfigurationError(str(e))
+            raise ConfigurationError(str(e)) from e
 
     @classmethod
     def from_dict(cls, data: dict[str, Any]) -> KatranConfig:
         """Load configuration from a dictionary."""
         try:
             return cls.model_validate(data)
         except Exception as e:
-            raise ConfigurationError(str(e))
+            raise ConfigurationError(str(e)) from e
 
     def validate_paths(self) -> list[str]:
         """

src/katran/core/types.py

@@ -141,10 +141,7 @@ def from_bytes(cls, data: bytes) -> VipKey:
             # Check if IPv6 (non-zero bytes after first 4)
             is_ipv6 = any(data[4:16])
 
-            if is_ipv6:
-                address = IPv6Address(data[:16])
-            else:
-                address = IPv4Address(data[:4])
+            address = IPv6Address(data[:16]) if is_ipv6 else IPv4Address(data[:4])
 
             # Port (2 bytes, network byte order)
             port = struct.unpack("!H", data[16:18])[0]
@@ -285,10 +282,7 @@ def from_bytes(cls, data: bytes) -> RealDefinition:
         try:
             flags = RealFlags(data[16])
 
-            if flags & RealFlags.IPV6:
-                address = IPv6Address(data[:16])
-            else:
-                address = IPv4Address(data[:4])
+            address = IPv6Address(data[:16]) if flags & RealFlags.IPV6 else IPv4Address(data[:4])
 
             return cls(address=address, flags=flags)
 

src/katran/lb/maglev.py

@@ -150,10 +150,7 @@ def _is_prime(n: int) -> bool:
         return True
     if n % 2 == 0:
         return False
-    for i in range(3, int(n**0.5) + 1, 2):
-        if n % i == 0:
-            return False
-    return True
+    return all(n % i != 0 for i in range(3, int(n ** 0.5) + 1, 2))
 
 
 def _gen_maglev_permutation(endpoint: Endpoint, ring_size: int) -> tuple[int, int]:
@@ -356,7 +353,7 @@ def rebuild(
         # Compute changes
         changes: dict[int, tuple[int, int]] = {}
         if old_ring and len(old_ring) == len(new_ring):
-            for i, (old_val, new_val) in enumerate(zip(old_ring, new_ring)):
+            for i, (old_val, new_val) in enumerate(zip(old_ring, new_ring, strict=False)):
                 if old_val != new_val:
                     changes[i] = (old_val, new_val)
 
@@ -434,7 +431,7 @@ def compute_ring_changes(old_ring: list[int], new_ring: list[int]) -> tuple[int,
     if len(old_ring) != len(new_ring):
         raise ValueError("Rings must be the same size")
 
-    changed = sum(1 for o, n in zip(old_ring, new_ring) if o != n)
+    changed = sum(1 for o, n in zip(old_ring, new_ring, strict=False) if o != n)
     percentage = (changed / len(old_ring)) * 100 if old_ring else 0.0
 
     return changed, percentage
@@ -468,7 +465,7 @@ def compute_ring_updates(old_ring: list[int], new_ring: list[int]) -> dict[int,
         raise ValueError("Rings must be the same size")
 
     updates: dict[int, int] = {}
-    for i, (old_val, new_val) in enumerate(zip(old_ring, new_ring)):
+    for i, (old_val, new_val) in enumerate(zip(old_ring, new_ring, strict=False)):
         if old_val != new_val:
             updates[i] = new_val
 

tests/conftest.py

@@ -5,6 +5,7 @@
 import tempfile
 from ipaddress import IPv4Address, IPv6Address
 from pathlib import Path
+from unittest.mock import MagicMock
 
 import pytest
 
@@ -19,6 +20,9 @@
     VipKey,
     VipMeta,
 )
+from katran.lb.maglev import MaglevHashRing
+from katran.lb.real_manager import RealManager
+from katran.lb.vip_manager import VipManager
 
 # =============================================================================
 # Sample Data Fixtures
@@ -177,24 +181,6 @@ def items(self):
         return list(self._data.items())
 
 
-@pytest.fixture
-def mock_vip_map() -> MockBpfMap:
-    """Mock VIP map."""
-    return MockBpfMap(key_size=20, value_size=8)
-
-
-@pytest.fixture
-def mock_reals_map() -> MockBpfMap:
-    """Mock reals map."""
-    return MockBpfMap(key_size=4, value_size=20)
-
-
-@pytest.fixture
-def mock_ch_rings_map() -> MockBpfMap:
-    """Mock consistent hash rings map."""
-    return MockBpfMap(key_size=4, value_size=4)
-
-
 @pytest.fixture
 def mock_stats_map() -> MockBpfMap:
     """Mock statistics map."""
@@ -205,12 +191,6 @@ def mock_stats_map() -> MockBpfMap:
 # Manager Fixtures (for Phase 2 unit tests)
 # =============================================================================
 
-from unittest.mock import MagicMock
-
-from katran.lb.maglev import MaglevHashRing
-from katran.lb.real_manager import RealManager
-from katran.lb.vip_manager import VipManager
-
 
 @pytest.fixture
 def mock_vip_map():

tests/e2e/conftest.py

@@ -78,7 +78,7 @@ def api_client(api_url) -> httpx.Client:
     client = httpx.Client(base_url=api_url, timeout=30.0)
 
     # Wait for API readiness
-    for attempt in range(30):
+    for _attempt in range(30):
         try:
             resp = client.get("/health")
             if resp.status_code == 200: