chore(api): add mypy coverage to cli/stack (#2650)

# What does this PR do?
<!-- Provide a short summary of what this PR does and why. Link to
relevant issues if applicable. -->
This PR adds static type coverage to `llama-stack`

Part of https://github.com/meta-llama/llama-stack/issues/2647

<!-- 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.* -->

Signed-off-by: Mustafa Elbehery <melbeher@redhat.com>

llama_stack/cli/stack/_build.py

@@ -93,7 +93,7 @@ def run_stack_build_command(args: argparse.Namespace) -> None:
             )
             sys.exit(1)
     elif args.providers:
-        providers = dict()
+        providers_list: dict[str, str | list[str]] = dict()
         for api_provider in args.providers.split(","):
             if "=" not in api_provider:
                 cprint(
@@ -112,7 +112,15 @@ def run_stack_build_command(args: argparse.Namespace) -> None:
                 )
                 sys.exit(1)
             if provider in providers_for_api:
-                providers.setdefault(api, []).append(provider)
+                if api not in providers_list:
+                    providers_list[api] = []
+                # Use type guarding to ensure we have a list
+                provider_value = providers_list[api]
+                if isinstance(provider_value, list):
+                    provider_value.append(provider)
+                else:
+                    # Convert string to list and append
+                    providers_list[api] = [provider_value, provider]
             else:
                 cprint(
                     f"{provider} is not a valid provider for the {api} API.",
@@ -121,7 +129,7 @@ def run_stack_build_command(args: argparse.Namespace) -> None:
                 )
                 sys.exit(1)
         distribution_spec = DistributionSpec(
-            providers=providers,
+            providers=providers_list,
             description=",".join(args.providers),
         )
         if not args.image_type:
@@ -182,7 +190,7 @@ def run_stack_build_command(args: argparse.Namespace) -> None:
 
         cprint("Tip: use <TAB> to see options for the providers.\n", color="green", file=sys.stderr)
 
-        providers = dict()
+        providers: dict[str, str | list[str]] = dict()
         for api, providers_for_api in get_provider_registry().items():
             available_providers = [x for x in providers_for_api.keys() if x not in ("remote", "remote::sample")]
             if not available_providers:
@@ -371,10 +379,16 @@ def _run_stack_build_command_from_build_config(
         if not image_name:
             raise ValueError("Please specify an image name when building a venv image")
 
+    # At this point, image_name should be guaranteed to be a string
+    if image_name is None:
+        raise ValueError("image_name should not be None after validation")
+
     if template_name:
         build_dir = DISTRIBS_BASE_DIR / template_name
         build_file_path = build_dir / f"{template_name}-build.yaml"
     else:
+        if image_name is None:
+            raise ValueError("image_name cannot be None")
         build_dir = DISTRIBS_BASE_DIR / image_name
         build_file_path = build_dir / f"{image_name}-build.yaml"
 
@@ -395,7 +409,7 @@ def _run_stack_build_command_from_build_config(
         build_file_path,
         image_name,
         template_or_config=template_name or config_path or str(build_file_path),
-        run_config=run_config_file,
+        run_config=run_config_file.as_posix() if run_config_file else None,
     )
     if return_code != 0:
         raise RuntimeError(f"Failed to build image {image_name}")

pyproject.toml

@@ -226,7 +226,6 @@ follow_imports = "silent"
 exclude = [
     # As we fix more and more of these, we should remove them from the list
     "^llama_stack/cli/download\\.py$",
-    "^llama_stack/cli/stack/_build\\.py$",
     "^llama_stack/distribution/build\\.py$",
     "^llama_stack/distribution/client\\.py$",
     "^llama_stack/distribution/request_headers\\.py$",