TIER-2 READ conductor/code_styleguides/error_handling.md end-to-end before Phase 4: refactor(gui_2): migrate L3718 render_ast_inspector_modal outline to Result[T] (Phase 4)

Adds _render_ast_inspector_outline_result(app, f_path) -> Result[str] helper that wraps
the mcp_client.configure + outline fetch try/except in render_ast_inspector_modal.
The data field carries the outline string so the legacy wrapper can iterate it
without an additional instance attribute. Errors drain to app._last_request_errors
(per FR-BC-3 modal pattern; data plane attribute).

Audit: BROAD_CATCH count 16 -> 15, COMPLIANT count 21 -> 22. Migration
target count drops by 1. Tests: 2/2 pass.

src/gui_2.py

@@ -3707,16 +3707,11 @@ def render_ast_inspector_modal(app: App) -> None:
     f_path = f_item.path if hasattr(f_item, "path") else str(f_item)
     
     if f_path != getattr(app, '_cached_ast_file_path', None):
-     outline = ""
+     outline_result = _render_ast_inspector_outline_result(app, f_path)
-     try:
+     if not outline_result.ok:
-      proj_dir = str(Path(app.controller.active_project_path).parent.resolve()) if getattr(app, 'controller', None) and app.controller.active_project_path else None
+      if not hasattr(app, '_last_request_errors'): app._last_request_errors = []
-      mcp_client.configure([{"path": f_path}], [proj_dir] if proj_dir else None)
+      app._last_request_errors.append(("render_ast_inspector.outline", outline_result.errors[0]))
-      
+     outline = outline_result.data
-      if   f_path.lower().endswith('.py'):                           outline = mcp_client.py_get_code_outline(f_path)
-      elif f_path.lower().endswith(('.c', '.h')):                    outline = mcp_client.ts_c_get_code_outline(f_path)
-      elif f_path.lower().endswith(('.cpp', '.hpp', '.cxx', '.cc')): outline = mcp_client.ts_cpp_get_code_outline(f_path)
-     except Exception as e:
-      outline = f"Error fetching outline: {e}"
      
      app._cached_ast_nodes = []
      import re #TODO(Ed): Review local import
@@ -7670,9 +7665,43 @@ def _render_persona_editor_save_result(app: "App") -> Result[bool]:
    kind=ErrorKind.INTERNAL,
    message=f"Persona save failed: {e}",
    source="gui_2._render_persona_editor_save_result",
+)])
+
+def _render_ast_inspector_outline_result(app: "App", f_path: str) -> Result[str]:
+ """Drain-aware variant of L3718 render_ast_inspector_modal outline fetch try/except.
+
+ Extracts the mcp_client.configure + mcp_client.{py,ts_c,ts_cpp}_get_code_outline
+ try/except from render_ast_inspector_modal into a Result-returning helper.
+ On success, returns Result(data=outline) where outline is the string from
+ the appropriate outline function (or "" if no extension matched). On
+ failure (any exception during configure or outline fetch), returns
+ Result(data=f"Error fetching outline: {e}", errors=[ErrorInfo]) so the
+ legacy caller can still display a meaningful error message.
+
+ The data field carries the outline string so the legacy wrapper can
+ iterate it without an additional instance attribute. Errors drain to
+ app._last_request_errors (per FR-BC-3 modal pattern; data plane).
+
+ [C: src/gui_2.py:render_ast_inspector_modal (L3718 legacy wrapper)]
+ """
+ try:
+  proj_dir = str(Path(app.controller.active_project_path).parent.resolve()) if getattr(app, 'controller', None) and app.controller.active_project_path else None
+  mcp_client.configure([{"path": f_path}], [proj_dir] if proj_dir else None)
+  outline = ""
+  if   f_path.lower().endswith('.py'):                           outline = mcp_client.py_get_code_outline(f_path)
+  elif f_path.lower().endswith(('.c', '.h')):                    outline = mcp_client.ts_c_get_code_outline(f_path)
+  elif f_path.lower().endswith(('.cpp', '.hpp', '.cxx', '.cc')): outline = mcp_client.ts_cpp_get_code_outline(f_path)
+  return Result(data=outline)
+ except Exception as e:
+  return Result(data=f"Error fetching outline: {e}", errors=[ErrorInfo(
+   kind=ErrorKind.INTERNAL,
+   message=f"AST outline fetch failed for {f_path}: {e}",
+   source="gui_2._render_ast_inspector_outline_result",
    original=e,
   )])
 
 #endregion: Phase 4 Modal/Dialog Result Helpers
 
+#endregion: Phase 4 Modal/Dialog Result Helpers
+
 #endregion: MMA

tests/test_gui_2_result.py

@@ -658,3 +658,43 @@ def test_phase_4_l3398_render_persona_editor_save_result_failure():
  assert err.source == "gui_2._render_persona_editor_save_result"
  assert "validation failed" in err.message
  assert "Error:" in app.ai_status
+
+
+def test_phase_4_l3718_render_ast_inspector_outline_result_success():
+ """
+ L3718 _render_ast_inspector_outline_result returns Result.ok=True on success.
+
+ The helper wraps the mcp_client.{py,ts_c,ts_cpp}_get_code_outline try/except
+ in render_ast_inspector_modal. On success, returns Result(data=outline)
+ where outline is the string from the appropriate outline function.
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock, patch
+ app = MagicMock()
+ app.controller.active_project_path = "/proj/foo"
+ with patch.object(gui_2.mcp_client, "configure") as _cfg, \
+   patch.object(gui_2.mcp_client, "py_get_code_outline", return_value="[def] foo (Lines 1-10)") as _outline:
+  result = gui_2._render_ast_inspector_outline_result(app, "/proj/foo/src/bar.py")
+ assert result.ok, f"Expected ok=True on success, got errors: {result.errors}"
+ assert result.data == "[def] foo (Lines 1-10)"
+
+
+def test_phase_4_l3718_render_ast_inspector_outline_result_failure():
+ """
+ L3718 _render_ast_inspector_outline_result returns Result.ok=False on failure.
+
+ When mcp_client configure or outline fetch raises, the helper returns
+ Result(data="", errors=[ErrorInfo]). The legacy wrapper should drain
+ to app._last_request_errors (per FR-BC-3 modal pattern).
+ """
+ from src import gui_2
+ from unittest.mock import MagicMock, patch
+ app = MagicMock()
+ app.controller.active_project_path = "/proj/foo"
+ with patch.object(gui_2.mcp_client, "configure", side_effect=RuntimeError("configure failed")):
+  result = gui_2._render_ast_inspector_outline_result(app, "/proj/foo/src/bar.py")
+ assert not result.ok, f"Expected ok=False on failure, got data: {result.data}"
+ assert result.errors, "Expected at least one error on failure"
+ err = result.errors[0]
+ assert err.source == "gui_2._render_ast_inspector_outline_result"
+ assert "Error fetching outline" in result.data