[BUG] search request with ml_inference response processor search pipeline throws error with script_fields

[prasadnu]

Describe the bug

Currently, through ml_inference response processor, I can access only the _source fields in the input_map. If I create new fields using a script while querying, I get illegal_argument_exception error

Related component

No response

To Reproduce

Example:

Creating search pipeline with ml_inference response processor

PUT /_search/pipeline/LLM_language_detection_pipeline
{
"description": "Translate the text",
"response_processors": [
{
"ml_inference": {
"model_id": "3oDXrJQBHuI4hsXgXABB",
"input_map": [
{
"inputs": "new_field". ##### using the script field as the model input
}
],
"output_map": [
{
"ext.ml_inference.llm_response": "response"
}
]
}
}
]
}

_search query that creates a script field, 'new_field':

GET /_search?search_pipeline=LLM_language_detection_pipeline
{
"query": {
"match_all": {}
},
"script_fields": {
"new_field": {
"script": {
"lang": "painless",
"source": "'new_field_value'"
}
}
}
}

Response

{
"error": {
"root_cause": [
{
"type": "illegal_argument_exception",
"reason": "json object can not be null"
}
],
"type": "illegal_argument_exception",
"reason": "json object can not be null"
},
"status": 400
}

Expected behavior

search request with ml_inference response processor search pipeline to be able to run with script_fields

Additional Details

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• OS: [e.g. iOS]
• Version [e.g. 22]

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