fix: address PR #49 review (preserve dict keys, role test, parser type)

Return validated input dict instead of reconstructing four keys.
Add test_missing_role_in_message and annotate build_cli_parser().

Author: clean6378-max-it

app.py

@@ -1,5 +1,6 @@
 """Flask app that serves the web GUI for browsing sessions."""
 
+import argparse
 import os
 import sys
 
@@ -35,10 +36,8 @@ def index():
     return app
 
 
-def build_cli_parser():
+def build_cli_parser() -> argparse.ArgumentParser:
     """CLI argument parser for ``python app.py`` (stdlib only; safe to import in tests)."""
-    import argparse
-
     parser = argparse.ArgumentParser(description="Claude Code Chat Browser")
     parser.add_argument("--port", type=int, default=5000)
     parser.add_argument("--host", default="127.0.0.1")

tests/test_jsonl_validation.py

@@ -46,6 +46,13 @@ def test_null_role_in_message(self):
             )
         assert exc_info.value.path == "messages[0].role"
 
+    def test_missing_role_in_message(self):
+        with pytest.raises(SessionValidationError) as exc_info:
+            validate_session_dict(
+                _valid_payload(messages=[{"text": "no role key"}])
+            )
+        assert exc_info.value.path == "messages[0].role"
+
     def test_metadata_not_dict(self):
         with pytest.raises(SessionValidationError) as exc_info:
             validate_session_dict(_valid_payload(metadata="not-a-dict"))

utils/validation.py

@@ -3,13 +3,14 @@
 from typing import Any, cast
 
 from models.errors import SessionValidationError
-from models.session import MessageDict, SessionDict
+from models.session import SessionDict
 
 _REQUIRED_SESSION_KEYS = ("session_id", "title", "messages", "metadata")
 
 
 def validate_session_dict(data: dict[str, Any]) -> SessionDict:
     """Validate a plain dict matches SessionDict before returning it."""
+    # Runtime guard for dynamic callers; mypy already types the parameter as dict.
     if not isinstance(data, dict):
         raise SessionValidationError("$", "expected dict")
 
@@ -18,6 +19,7 @@ def validate_session_dict(data: dict[str, Any]) -> SessionDict:
             raise SessionValidationError(key, "missing required field")
 
     session_id = data["session_id"]
+    # Explicit null check before isinstance so errors say "must not be null".
     if session_id is None:
         raise SessionValidationError("session_id", "must not be null")
     if not isinstance(session_id, str):
@@ -67,12 +69,4 @@ def validate_session_dict(data: dict[str, Any]) -> SessionDict:
             "metadata", f"expected dict, got {type(metadata).__name__}"
         )
 
-    return cast(
-        SessionDict,
-        {
-            "session_id": session_id,
-            "title": title,
-            "messages": cast(list[MessageDict], messages),
-            "metadata": metadata,
-        },
-    )
+    return cast(SessionDict, data)