Promote 7 ty rules from ignore to warn, fix 9 violations (#3852)

Enables stricter type checking by promoting rules that default to
ignore: division-by-zero, possibly-missing-attribute,
possibly-missing-import, possibly-unresolved-reference,
unsupported-dynamic-base, unsupported-operator, unused-ignore-comment.

6 of the 7 rules had zero violations. possibly-unresolved-reference
had 9 (5 in src/, 3 in tests/, 1 walrus-operator false positive
suppressed with ty: ignore).

🤖 Generated with Claude Code

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

pyproject.toml

@@ -162,6 +162,15 @@ python-version = "3.10"
 # Some code uses `# ty: ignore[invalid-argument-type]` for this limitation.
 # TODO: Remove these ignores once ty supports union narrowing
 
+# Promote rules from default-ignore to warn (becomes error via error-on-warning)
+division-by-zero = "warn"
+possibly-missing-attribute = "warn"
+possibly-missing-import = "warn"
+possibly-unresolved-reference = "warn"
+unsupported-dynamic-base = "warn"
+unsupported-operator = "warn"
+unused-ignore-comment = "warn"
+
 [tool.ty.terminal]
 error-on-warning = true
 

src/fastmcp/mcp_config.py

@@ -322,7 +322,7 @@ class MCPConfig(BaseModel):
     def from_file(cls, file_path: Path) -> Self:
         """Load configuration from JSON file."""
         if file_path.exists() and (content := file_path.read_text().strip()):
-            return cls.model_validate_json(content)
+            return cls.model_validate_json(content)  # ty: ignore[possibly-unresolved-reference]
 
         raise ValueError(f"No MCP servers defined in the config: {file_path}")
 

src/fastmcp/utilities/openapi/schemas.py

@@ -247,7 +247,8 @@ def _combine_schemas_and_map_params(
         "header": set(),
         "cookie": set(),
     }
-    body_props = {}
+    body_schema: dict[str, Any] = {}
+    body_props: dict[str, Any] = {}
 
     for param in route.parameters:
         param_names_by_location[param.location].add(param.name)

tests/server/test_input_validation.py

@@ -146,6 +146,7 @@ class TestPydanticModelArguments:
             )
 
             # This test verifies whether we handle stringified JSON
+            error_msg = ""
             try:
                 result = await client.call_tool("create_user", {"profile": stringified})
                 # If this succeeds, we're handling stringified JSON

tests/utilities/json_schema_type/test_real_world_schemas.py

@@ -206,6 +206,7 @@ def _test_provider(provider: str) -> ProviderResult:
 
             result.schemas += 1
 
+            old_handler = signal.SIG_DFL
             if use_alarm:
                 old_handler = signal.signal(signal.SIGALRM, _alarm_handler)
                 signal.alarm(SCHEMA_TIMEOUT)