fix: add TableInput validation for single dict and Data instances (#6136)

* fix: enhance TableInput validation to support single dict and Data instances

* [autofix.ci] apply automated fixes

* fix: Improve TableInput validation error handling

Change TypeError to ValueError for Pydantic validation to ensure proper error catching. Added noqa comments to suppress linting warnings about error type.

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Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Ítalo Johnny <italojohnnydosanjos@gmail.com>

src/backend/base/langflow/inputs/inputs.py

@@ -37,20 +37,34 @@ class TableInput(BaseInputMixin, MetadataTraceMixin, TableMixin, ListableInputMi
     @field_validator("value")
     @classmethod
     def validate_value(cls, v: Any, _info):
-        # Check if value is a list of dicts
+        # Convert single dict or Data instance into a list.
+        if isinstance(v, dict | Data):
+            v = [v]
+        # Automatically convert DataFrame into a list of dictionaries.
         if isinstance(v, DataFrame):
             v = v.to_dict(orient="records")
+        # Verify the value is now a list.
         if not isinstance(v, list):
-            msg = f"TableInput value must be a list of dictionaries or Data. Value '{v}' is not a list."
-            raise ValueError(msg)  # noqa: TRY004
-
-        for item in v:
+            msg = (
+                "The table input must be a list of rows. You provided a "
+                f"{type(v).__name__}, which cannot be converted to table format. "
+                "Please provide your data as either:\n"
+                "- A list of dictionaries (each dict is a row)\n"
+                "- A pandas DataFrame\n"
+                "- A single dictionary (will become a one-row table)\n"
+                "- A Data object (Langflow's internal data structure)\n"
+            )
+            raise ValueError(msg)  # noqa: TRY004 Pydantic only catches ValueError or AssertionError
+        # Ensure each item in the list is either a dict or a Data instance.
+        for i, item in enumerate(v):
             if not isinstance(item, dict | Data):
                 msg = (
-                    "TableInput value must be a list of dictionaries or Data. "
-                    f"Item '{item}' is not a dictionary or Data."
+                    f"Row {i + 1} in your table has an invalid format. Each row must be either:\n"
+                    "- A dictionary containing column name/value pairs\n"
+                    "- A Data object (Langflow's internal data structure for passing data between components)\n"
+                    f"Instead, got a {type(item).__name__}. Please check the format of your input data."
                 )
-                raise ValueError(msg)  # noqa: TRY004
+                raise ValueError(msg)  # noqa: TRY004 Pydantic only catches ValueError or AssertionError
         return v