doc: enhance ui and error documentation

Author: yimingyinqwqq

kani-driver/src/args/mod.rs

@@ -242,6 +242,8 @@ pub struct VerificationArgs {
     #[arg(long)]
     pub default_unwind: Option<u32>,
 
+    /// Output the verification results to a JSON file at the specified path.
+    /// This feature is unstable and it requires `-Z unstable-options` to be used
     #[arg(long)]
     pub export_json: Option<PathBuf>,
 

scripts/validate_json_export.py

@@ -153,12 +153,16 @@ def validate_field_path(json_file, field_path, schema=None):
 
     for part in parts:
         if part not in current_data:
-            print(f"ERROR: Field path '{field_path}' not found in data")
+            print(
+                f"ERROR: Field path '{field_path}' not found in data. Missing part: '{part}'"
+            )
             return False
         current_data = current_data[part]
 
         if part not in current_schema:
-            print(f"ERROR: Field path '{field_path}' not found in schema template")
+            print(
+                f"ERROR: Field path '{field_path}' not found in schema template. Missing part: '{part}'"
+            )
             return False
         current_schema = current_schema[part]