ci: add mypy for static type checking (#1101)

# What does this PR do?

- Enable mypy to run in the CI on a subset of the repository
- Fix a few mypy errors
- Run mypy from pre-commit

Signed-off-by: Sébastien Han <seb@redhat.com>
 
[//]: # (If resolving an issue, uncomment and update the line below)
[//]: # (Closes #[issue-number])

## Test Plan
[Describe the tests you ran to verify your changes with result
summaries. *Provide clear instructions so the plan can be easily
re-executed.*]

[//]: # (## Documentation)

Signed-off-by: Sébastien Han <seb@redhat.com>

llama_stack/apis/common/type_system.py

@@ -91,15 +91,18 @@ ParamType = register_schema(
     name="ParamType",
 )
 
+"""
 # TODO: recursive definition of ParamType in these containers
 # will cause infinite recursion in OpenAPI generation script
 # since we are going with ChatCompletionInputType and CompletionInputType
 # we don't need to worry about ArrayType/ObjectType/UnionType for now
-# ArrayType.model_rebuild()
-# ObjectType.model_rebuild()
-# UnionType.model_rebuild()
+ArrayType.model_rebuild()
+ObjectType.model_rebuild()
+UnionType.model_rebuild()
 
 
-# class CustomType(BaseModel):
-#     type: Literal["custom"] = "custom"
-#     validator_class: str
+class CustomType(BaseModel):
+pylint: disable=syntax-error
+    type: Literal["custom"] = "custom"
+    validator_class: str
+"""

llama_stack/schema_utils.py

@@ -5,12 +5,10 @@
 # the root directory of this source tree.
 
 from dataclasses import dataclass
-from typing import Any, Callable, List, Optional, TypeVar
+from typing import Any, Callable, List, Optional, Protocol, TypeVar
 
 from .strong_typing.schema import json_schema_type, register_schema  # noqa: F401
 
-T = TypeVar("T")
-
 
 @dataclass
 class WebMethod:
@@ -22,6 +20,13 @@ class WebMethod:
     raw_bytes_request_body: Optional[bool] = False
 
 
+class HasWebMethod(Protocol):
+    __webmethod__: WebMethod
+
+
+T = TypeVar("T", bound=HasWebMethod)  # Bound T to classes that match this protocol
+
+
 def webmethod(
     route: Optional[str] = None,
     method: Optional[str] = None,

llama_stack/scripts/distro_codegen.py

@@ -11,7 +11,7 @@ import subprocess
 import sys
 from functools import partial
 from pathlib import Path
-from typing import Iterator
+from typing import Iterable
 
 from rich.progress import Progress, SpinnerColumn, TextColumn
 
@@ -39,7 +39,7 @@ class ChangedPathTracker:
         return self._changed_paths
 
 
-def find_template_dirs(templates_dir: Path) -> Iterator[Path]:
+def find_template_dirs(templates_dir: Path) -> Iterable[Path]:
     """Find immediate subdirectories in the templates folder."""
     if not templates_dir.exists():
         raise FileNotFoundError(f"Templates directory not found: {templates_dir}")
@@ -90,7 +90,7 @@ def check_for_changes(change_tracker: ChangedPathTracker) -> bool:
     return has_changes
 
 
-def collect_template_dependencies(template_dir: Path) -> tuple[str, list[str]]:
+def collect_template_dependencies(template_dir: Path) -> tuple[str | None, list[str]]:
     try:
         module_name = f"llama_stack.templates.{template_dir.name}"
         module = importlib.import_module(module_name)

llama_stack/scripts/run_client_sdk_tests.py

@@ -52,7 +52,7 @@ def main(parser: argparse.ArgumentParser):
                     pytest_args,
                     "-s",
                     "-v",
-                    REPO_ROOT / CLIENT_SDK_TESTS_RELATIVE_PATH,
+                    str(REPO_ROOT / CLIENT_SDK_TESTS_RELATIVE_PATH),
                 ]
             )