adding the OpenAIFunctionCaller

[TuanaCelik]

Proposed Changes:

I propose adding this OpenAIFunctionCaller component that is able to accept a list of ChatMessages, and run a function if there were any tool_calls within these messages.

Some simple guardrails that have been added:
If the tool/function name in the message that we get doesn't actually exist (hallucinated) , the component returns an assistant message indicating as such.

How did you test it?

Manual tests. Here is the pipeline I'm using:

message_collector = BranchJoiner(List[ChatMessage])
chat_generator = OpenAIChatGenerator(model="gpt-3.5-turbo", generation_kwargs={'tools': tools})
function_caller = OpenAIFunctionCaller(available_functions={"rag_pipeline_func": rag_pipeline_func, 
                                                            "get_current_weather": get_current_weather})

function_calling_pipeline = Pipeline()
function_calling_pipeline.add_component("message_collector", message_collector)
function_calling_pipeline.add_component("generator", chat_generator)
function_calling_pipeline.add_component("function_caller", function_caller)

function_calling_pipeline.connect("message_collector", "generator.messages")
function_calling_pipeline.connect("generator", "function_caller")
function_calling_pipeline.connect("function_caller.function_replies", "message_collector")

messages = [
    ChatMessage.from_system(
        """If needed, break down the users question to simpler questions and follow up questions that you can use with your tools.
        Don't make assumptions about what values to plug into functions. Ask for clarification if a user request is ambiguous."""
    )
]
while True:
  user_input = input("INFO: Type 'exit' or 'quit' to stop\n")
  if user_input.lower() == "exit" or user_input.lower() == "quit":
    break
  messages.append(ChatMessage.from_user(user_input))
  response = function_calling_pipeline.run({"message_collector": {"value": messages}})
  messages.extend(response['function_caller']['assistant_replies'])
  print(response['function_caller']['assistant_replies'][0])

Notes for the reviewer

You can try this pipeline here

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[coveralls]

Pull Request Test Coverage Report for Build 9513906991

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• Overall coverage remained the same at 97.764%

---

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

---

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[masci]

Took a first pass, this will be tricky to serialize but doable

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Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

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---

Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

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• Overall coverage remained the same at 97.764%

---

Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

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---

Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

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Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
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Relevant Lines:	626

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Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

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Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
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Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

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Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

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[masci]

Good on my side

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• Overall coverage remained the same at 97.764%

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Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

---

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Pull Request Test Coverage Report for Build 9560720590

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• Overall coverage remained the same at 97.764%

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Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

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Pull Request Test Coverage Report for Build 9563066747

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
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• Overall coverage remained the same at 97.764%

---

Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

---

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[coveralls]

Pull Request Test Coverage Report for Build 9563287676

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 10 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 97.764%

---

Files with Coverage Reduction	New Missed Lines	%
haystack_experimental/evaluation/harness/rag/harness.py	10	91.87%

Totals
Change from base Build 9465387731:	0.0%
Covered Lines:	612
Relevant Lines:	626

---

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[coveralls]

Pull Request Test Coverage Report for Build 9564264800

Details

• 79 of 83 (95.18%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 97.461%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
test/components/tools/openai/test_function_caller.py	34	35	97.14%
haystack_experimental/components/tools/openai/function_caller.py	39	42	92.86%

Totals
Change from base Build 9516119182:	-0.3%
Covered Lines:	691
Relevant Lines:	709

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9564511117

Details

• 79 of 83 (95.18%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 97.461%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
test/components/tools/openai/test_function_caller.py	34	35	97.14%
haystack_experimental/components/tools/openai/function_caller.py	39	42	92.86%

Totals
Change from base Build 9516119182:	-0.3%
Covered Lines:	691
Relevant Lines:	709

---

💛 - Coveralls