feat: Add new LLMEvaluator component (#7401)

* draft llm evaluator

* docstrings

* flexible inputs; validate inputs and outputs

* add tests

* add release note

* remove example

* docstrings

* make outputs parameter optional. default:

* validate init parameters

* linting

* remove mention of binary scores from template

* make examples and outputs params non-optional

* removed leftover from optional outputs param

* simplify building examples section for template

* validate inputs and outputs in examples are dict with str as key

* fix pylint too-many-boolean-expressions

* increase test coverage
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from .answer_exact_match import AnswerExactMatchEvaluator
from .llm_evaluator import LLMEvaluator
__all__ = ["AnswerExactMatchEvaluator"]
__all__ = ["AnswerExactMatchEvaluator", "LLMEvaluator"]

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import json
from typing import Any, Dict, List, Tuple, Type
from haystack import component, default_from_dict, default_to_dict
from haystack.components.builders import PromptBuilder
from haystack.components.generators import OpenAIGenerator
from haystack.utils import Secret, deserialize_secrets_inplace
@component
class LLMEvaluator:
"""
Uses an LLM to evaluate inputs based on a prompt containing instructions and examples.
The default API requires an OpenAI API key to be provided as an environment variable "OPENAI_API_KEY".
The inputs are lists that are user-defined depending on the desired metric.
The output is a dictionary with a key `results` containing a list of evaluation results.
Each result is a dictionary with user-defined keys and values of either 0 for FALSE or 1 for TRUE respectively.
Usage example:
```python
from haystack.components.evaluators import LLMEvaluator
evaluator = LLMEvaluator(
instructions="Is this answer problematic for children?",
inputs=[("responses", List[str])],
outputs=["score"],
)
RESPONSES = [
"Football is the most popular sport with around 4 billion followers worldwide",
"Python language was created by Guido van Rossum.",
]
results = evaluator.run(responses=RESPONSES)
```
"""
def __init__(
self,
instructions: str,
inputs: List[Tuple[str, Type[List]]],
outputs: List[str],
examples: List[Dict[str, Any]],
*,
api: str = "openai",
api_key: Secret = Secret.from_env_var("OPENAI_API_KEY"),
):
"""
Creates an instance of LLMEvaluator.
:param instructions:
The prompt instructions to use for evaluation.
Should be a question about the inputs that can be answered with yes or no.
:param inputs:
The inputs that the component expects as incoming connections and that it evaluates.
Each input is a tuple of an input name and input type. Input types must be lists.
:param outputs:
Output names of the evaluation results. They correspond to keys in the output dictionary.
The default is a single key "score".
:param examples:
Few-shot examples conforming to the expected input and output format as defined in the `inputs` and
`outputs` parameters.
Each example is a dictionary with keys "inputs" and "outputs"
They contain the input and output as dictionaries respectively.
:param api:
The API to use for calling an LLM through a Generator.
Supported APIs: "openai".
:param api_key:
The API key.
"""
self.validate_init_parameters(inputs, outputs, examples)
self.instructions = instructions
self.inputs = inputs
self.outputs = outputs
self.examples = examples
self.api = api
self.api_key = api_key
if api == "openai":
self.generator = OpenAIGenerator(api_key=api_key)
else:
raise ValueError(f"Unsupported API: {api}")
template = self.prepare_template()
self.builder = PromptBuilder(template=template)
component.set_input_types(self, **dict(inputs))
def validate_init_parameters(
self, inputs: List[Tuple[str, Type[List]]], outputs: List[str], examples: List[Dict[str, Any]]
):
"""
Validate the init parameters.
:param inputs:
The inputs to validate.
:param outputs:
The outputs to validate.
:param examples:
The examples to validate.
:raises ValueError:
If the inputs are not a list of tuples with a string and a type of list.
If the outputs are not a list of strings.
If the examples are not a list of dictionaries.
If any example does not have keys "inputs" and "outputs" with values that are dictionaries with string keys.
"""
# Validate inputs
if (
not isinstance(inputs, list)
or not all(isinstance(input, tuple) for input in inputs)
or not all(isinstance(input[0], str) and input[1] is not list and len(input) == 2 for input in inputs)
):
msg = (
f"LLM evaluator expects inputs to be a list of tuples. Each tuple must contain an input name and "
f"type of list but received {inputs}."
)
raise ValueError(msg)
# Validate outputs
if not isinstance(outputs, list) or not all(isinstance(output, str) for output in outputs):
msg = f"LLM evaluator expects outputs to be a list of str but received {outputs}."
raise ValueError(msg)
# Validate examples are lists of dicts
if not isinstance(examples, list) or not all(isinstance(example, dict) for example in examples):
msg = f"LLM evaluator expects examples to be a list of dictionaries but received {examples}."
raise ValueError(msg)
# Validate each example
for example in examples:
if (
{"inputs", "outputs"} != example.keys()
or not all(isinstance(example[param], dict) for param in ["inputs", "outputs"])
or not all(isinstance(key, str) for param in ["inputs", "outputs"] for key in example[param])
):
msg = (
f"LLM evaluator expects each example to have keys `inputs` and `outputs` with values that are "
f"dictionaries with str keys but received {example}."
)
raise ValueError(msg)
@component.output_types(results=List[Dict[str, Any]])
def run(self, **inputs) -> Dict[str, Any]:
"""
Run the LLM evaluator.
:param inputs:
The input values to evaluate. The keys are the input names and the values are lists of input values.
:returns:
A dictionary with a single `results` entry that contains a list of results.
Each result is a dictionary containing the keys as defined in the `outputs` parameter of the LLMEvaluator
and the evaluation results as the values.
"""
self.validate_input_parameters(dict(self.inputs), inputs)
# inputs is a dictionary with keys being input names and values being a list of input values
# We need to iterate through the lists in parallel for all keys of the dictionary
input_names, values = inputs.keys(), list(zip(*inputs.values()))
list_of_input_names_to_values = [dict(zip(input_names, v)) for v in values]
results = []
for input_names_to_values in list_of_input_names_to_values:
prompt = self.builder.run(**input_names_to_values)
result = self.generator.run(prompt=prompt["prompt"])
self.validate_outputs(expected=self.outputs, received=result["replies"][0])
parsed_result = json.loads(result["replies"][0])
parsed_result["name"] = "llm"
results.append(parsed_result)
return {"results": results}
def prepare_template(self) -> str:
"""
Combine instructions, inputs, outputs, and examples into one prompt template with the following format:
Instructions:
<instructions>
Generate the response in JSON format with the following keys:
<list of output keys>
Consider the instructions and the examples below to determine those values.
Examples:
<examples>
Inputs:
<inputs>
Outputs:
:returns:
The prompt template.
"""
inputs_section = (
"{" + ",".join([f'"{input_socket[0]}": {{{{ {input_socket[0]} }}}}' for input_socket in self.inputs]) + "}"
)
examples_section = "\n".join(
[
"Inputs:\n" + json.dumps(example["inputs"]) + "\nOutputs:\n" + json.dumps(example["outputs"])
for example in self.examples
]
)
return (
f"Instructions:\n"
f"{self.instructions}\n\n"
f"Generate the response in JSON format with the following keys:\n"
f"{json.dumps(self.outputs)}\n"
f"Consider the instructions and the examples below to determine those values.\n\n"
f"Examples:\n"
f"{examples_section}\n\n"
f"Inputs:\n"
f"{inputs_section}\n"
f"Outputs:\n"
)
def to_dict(self) -> Dict[str, Any]:
"""
Serialize this component to a dictionary.
:returns:
The serialized component as a dictionary.
"""
return default_to_dict(
self,
instructions=self.instructions,
inputs=self.inputs,
outputs=self.outputs,
examples=self.examples,
api=self.api,
api_key=self.api_key.to_dict(),
)
@classmethod
def from_dict(cls, data: Dict[str, Any]) -> "LLMEvaluator":
"""
Deserialize this component from a dictionary.
:param data:
The dictionary representation of this component.
:returns:
The deserialized component instance.
"""
deserialize_secrets_inplace(data["init_parameters"], keys=["api_key"])
return default_from_dict(cls, data)
@staticmethod
def validate_input_parameters(expected: Dict[str, Any], received: Dict[str, Any]) -> None:
"""
Validate the input parameters.
:param expected:
The expected input parameters.
:param received:
The received input parameters.
:raises ValueError:
If not all expected inputs are present in the received inputs
If the received inputs are not lists or have different lengths
"""
# Validate that all expected inputs are present in the received inputs
for param in expected.keys():
if param not in received:
msg = f"LLM evaluator expected input parameter '{param}' but received only {received.keys()}."
raise ValueError(msg)
# Validate that all received inputs are lists
if not all(isinstance(input, list) for input in received.values()):
msg = f"LLM evaluator expects all input values to be lists but received {[type(input) for input in received.values()]}."
raise ValueError(msg)
# Validate that all received inputs are of the same length
inputs = received.values()
length = len(next(iter(inputs)))
if not all(len(input) == length for input in inputs):
msg = (
f"LLM evaluator expects all input lists to have the same length but received {inputs} with lengths "
f"{[len(input) for input in inputs]}."
)
raise ValueError(msg)
@staticmethod
def validate_outputs(expected: List[str], received: str) -> None:
"""
Validate the output.
:param expected:
Names of expected outputs
:param received:
Names of received outputs
:raises ValueError:
If not all expected outputs are present in the received outputs
"""
parsed_output = json.loads(received)
if not all(output in parsed_output for output in expected):
msg = f"Expected response from LLM evaluator to be JSON with keys {expected}, got {received}."
raise ValueError(msg)

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---
features:
- |
Add a new LLMEvaluator component that leverages LLMs through the OpenAI api to evaluate pipelines.

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from typing import List
import pytest
from haystack.components.evaluators import LLMEvaluator
from haystack.utils.auth import Secret
class TestLLMEvaluator:
def test_init_default(self, monkeypatch):
monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
component = LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
assert component.api == "openai"
assert component.generator.client.api_key == "test-api-key"
assert component.instructions == "test-instruction"
assert component.inputs == [("responses", List[str])]
assert component.outputs == ["score"]
assert component.examples == [
{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}
]
def test_init_fail_wo_openai_api_key(self, monkeypatch):
monkeypatch.delenv("OPENAI_API_KEY", raising=False)
with pytest.raises(ValueError, match="None of the .* environment variables are set"):
LLMEvaluator(
api="openai",
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
def test_init_with_parameters(self):
component = LLMEvaluator(
instructions="test-instruction",
api_key=Secret.from_token("test-api-key"),
inputs=[("responses", List[str])],
outputs=["custom_score"],
api="openai",
examples=[
{"inputs": {"responses": "Damn, this is straight outta hell!!!"}, "outputs": {"custom_score": 1}},
{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"custom_score": 0}},
],
)
assert component.generator.client.api_key == "test-api-key"
assert component.api == "openai"
assert component.examples == [
{"inputs": {"responses": "Damn, this is straight outta hell!!!"}, "outputs": {"custom_score": 1}},
{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"custom_score": 0}},
]
assert component.instructions == "test-instruction"
assert component.inputs == [("responses", List[str])]
assert component.outputs == ["custom_score"]
def test_init_with_invalid_parameters(self, monkeypatch):
monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
# Invalid inputs
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs={("responses", List[str])},
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs=[(List[str], "responses")],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs=[List[str]],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs={("responses", str)},
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
# Invalid outputs
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs="score",
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=[["score"]],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
# Invalid examples
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples={
"inputs": {"responses": "Damn, this is straight outta hell!!!"},
"outputs": {"custom_score": 1},
},
)
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[
[{"inputs": {"responses": "Damn, this is straight outta hell!!!"}, "outputs": {"custom_score": 1}}]
],
)
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[
{"wrong_key": {"responses": "Damn, this is straight outta hell!!!"}, "outputs": {"custom_score": 1}}
],
)
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[
{
"inputs": [{"responses": "Damn, this is straight outta hell!!!"}],
"outputs": [{"custom_score": 1}],
}
],
)
with pytest.raises(ValueError):
LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[{"inputs": {1: "Damn, this is straight outta hell!!!"}, "outputs": {2: 1}}],
)
def test_to_dict_default(self, monkeypatch):
monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
component = LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
data = component.to_dict()
assert data == {
"type": "haystack.components.evaluators.llm_evaluator.LLMEvaluator",
"init_parameters": {
"api_key": {"env_vars": ["OPENAI_API_KEY"], "strict": True, "type": "env_var"},
"api": "openai",
"instructions": "test-instruction",
"inputs": [("responses", List[str])],
"outputs": ["score"],
"examples": [{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
},
}
def test_from_dict(self, monkeypatch):
monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
data = {
"type": "haystack.components.evaluators.llm_evaluator.LLMEvaluator",
"init_parameters": {
"api_key": {"env_vars": ["OPENAI_API_KEY"], "strict": True, "type": "env_var"},
"api": "openai",
"instructions": "test-instruction",
"inputs": [("responses", List[str])],
"outputs": ["score"],
"examples": [{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
},
}
component = LLMEvaluator.from_dict(data)
assert component.api == "openai"
assert component.generator.client.api_key == "test-api-key"
assert component.instructions == "test-instruction"
assert component.inputs == [("responses", List[str])]
assert component.outputs == ["score"]
assert component.examples == [
{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}
]
def test_to_dict_with_parameters(self, monkeypatch):
monkeypatch.setenv("ENV_VAR", "test-api-key")
component = LLMEvaluator(
instructions="test-instruction",
api_key=Secret.from_env_var("ENV_VAR"),
inputs=[("responses", List[str])],
outputs=["custom_score"],
api="openai",
examples=[
{"inputs": {"responses": "Damn, this is straight outta hell!!!"}, "outputs": {"custom_score": 1}},
{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"custom_score": 0}},
],
)
data = component.to_dict()
assert data == {
"type": "haystack.components.evaluators.llm_evaluator.LLMEvaluator",
"init_parameters": {
"api_key": {"env_vars": ["ENV_VAR"], "strict": True, "type": "env_var"},
"api": "openai",
"instructions": "test-instruction",
"inputs": [("responses", List[str])],
"outputs": ["custom_score"],
"examples": [
{"inputs": {"responses": "Damn, this is straight outta hell!!!"}, "outputs": {"custom_score": 1}},
{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"custom_score": 0}},
],
},
}
def test_run_with_different_lengths(self, monkeypatch):
monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
component = LLMEvaluator(
instructions="test-instruction",
inputs=[("questions", List[str]), ("responses", List[List[str]])],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
def generator_run(self, *args, **kwargs):
return {"replies": ['{"score": 0.5}']}
monkeypatch.setattr("haystack.components.generators.openai.OpenAIGenerator.run", generator_run)
with pytest.raises(ValueError):
component.run(questions=["What is the capital of Germany?"], responses=[["Berlin"], ["Paris"]])
with pytest.raises(ValueError):
component.run(
questions=["What is the capital of Germany?", "What is the capital of France?"], responses=[["Berlin"]]
)
def test_run_returns_parsed_result(self, monkeypatch):
monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
component = LLMEvaluator(
instructions="test-instruction",
inputs=[("questions", List[str]), ("responses", List[List[str]])],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
def generator_run(self, *args, **kwargs):
return {"replies": ['{"score": 0.5}']}
monkeypatch.setattr("haystack.components.generators.openai.OpenAIGenerator.run", generator_run)
results = component.run(questions=["What is the capital of Germany?"], responses=["Berlin"])
assert results == {"results": [{"score": 0.5, "name": "llm"}]}
def test_prepare_template(self, monkeypatch):
monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
component = LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[
{"inputs": {"responses": "Damn, this is straight outta hell!!!"}, "outputs": {"score": 1}},
{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}},
],
)
template = component.prepare_template()
assert (
template
== 'Instructions:\ntest-instruction\n\nGenerate the response in JSON format with the following keys:\n["score"]\nConsider the instructions and the examples below to determine those values.\n\nExamples:\nInputs:\n{"responses": "Damn, this is straight outta hell!!!"}\nOutputs:\n{"score": 1}\nInputs:\n{"responses": "Football is the most popular sport."}\nOutputs:\n{"score": 0}\n\nInputs:\n{"responses": {{ responses }}}\nOutputs:\n'
)
def test_invalid_input_parameters(self, monkeypatch):
monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
component = LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
# None of the expected parameters are received
with pytest.raises(ValueError):
component.validate_input_parameters(expected={"responses": List[str]}, received={"questions": List[str]})
# Only one but not all the expected parameters are received
with pytest.raises(ValueError):
component.validate_input_parameters(
expected={"responses": List[str], "questions": List[str]}, received={"questions": List[str]}
)
# Received inputs are not lists
with pytest.raises(ValueError):
component.validate_input_parameters(expected={"questions": List[str]}, received={"questions": str})
def test_invalid_outputs(self, monkeypatch):
monkeypatch.setenv("OPENAI_API_KEY", "test-api-key")
component = LLMEvaluator(
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)
with pytest.raises(ValueError):
component.validate_outputs(expected=["score", "another_expected_output"], received='{"score": 1.0}')
with pytest.raises(ValueError):
component.validate_outputs(expected=["score"], received='{"wrong_name": 1.0}')
def test_unsupported_api(self):
with pytest.raises(ValueError):
LLMEvaluator(
api="unsupported_api",
instructions="test-instruction",
inputs=[("responses", List[str])],
outputs=["score"],
examples=[{"inputs": {"responses": "Football is the most popular sport."}, "outputs": {"score": 0}}],
)