feat: Allow Connection of ChatGenerator to AnswerBuilder

[lbux]

Related Issues

• fixes Allow Chat Generators to connect to Answer Builder #7839

Proposed Changes:

This PR makes it possible to pass in a ChatMessage to AnswerBuilder

How did you test it?

Replicated str tests for ChatMessages.

Notes for the reviewer

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

[lbux]

ChatGenerators only return replies, so when you connect a ChatGenerator to an AnswerBuilder, you have to use llm -> answer_builder as shown here:
rag_pipeline.connect("llm", "answer_builder")

Why not add support for .meta in a ChatGenerator?

The metadata is already contained in a ChatMessage. If we add support for metadata output of the ChatGenerator, we will be sending redundant data.

[coveralls]

Pull Request Test Coverage Report for Build 9606421122

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 4 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.02%) to 90.176%

---

Files with Coverage Reduction	New Missed Lines	%
components/builders/answer_builder.py	1	98.33%
components/builders/chat_prompt_builder.py	1	98.41%
document_stores/types/filter_policy.py	2	84.21%

Totals
Change from base Build 9583192592:	0.02%
Covered Lines:	7022
Relevant Lines:	7787

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9606450913

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 4 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.02%) to 90.176%

---

Files with Coverage Reduction	New Missed Lines	%
components/builders/answer_builder.py	1	98.33%
components/builders/chat_prompt_builder.py	1	98.41%
document_stores/types/filter_policy.py	2	84.21%

Totals
Change from base Build 9583192592:	0.02%
Covered Lines:	7022
Relevant Lines:	7787

---

💛 - Coveralls

[julian-risch]

Thank you for your contribution @lbux . The PR looks quite good to me already! 👍 There are just four mypy issues we need to fix:

haystack/components/builders/answer_builder.py:110: error: Item "str" of "Union[str, ChatMessage]" has no attribute "meta"  [union-attr]
haystack/components/builders/answer_builder.py:111: error: Item "str" of "Union[str, ChatMessage]" has no attribute "content"  [union-attr]
haystack/components/builders/answer_builder.py:119: error: Argument 1 to "_extract_reference_idxs" of "AnswerBuilder" has incompatible type "object"; expected "str"  [arg-type]
haystack/components/builders/answer_builder.py:131: error: Argument 1 to "_extract_answer_string" of "AnswerBuilder" has incompatible type "object"; expected "str"  [arg-type]

In addition, we should extend the release note to explain a bit more that the AnswerBuilder now accepts ChatMessages as input in addition to strings and that the metadata of the ChatMessage will be added to the Answer. Please let me know if you need any help here. Happy to address these change requests and pushing the PR over the finish line. 🙂

[coveralls]

Pull Request Test Coverage Report for Build 9668079863

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 101 unchanged lines in 11 files lost coverage.
• Overall coverage decreased (-0.2%) to 89.975%

---

Files with Coverage Reduction	New Missed Lines	%
components/builders/answer_builder.py	1	98.36%
components/builders/chat_prompt_builder.py	1	98.41%
components/evaluators/document_map.py	1	96.15%
components/evaluators/document_mrr.py	1	95.45%
core/component/component.py	2	98.28%
document_stores/types/filter_policy.py	2	84.21%
components/converters/pypdf.py	6	90.0%
components/evaluators/sas_evaluator.py	8	63.33%
document_stores/in_memory/document_store.py	9	97.02%
utils/hf.py	20	83.89%

Totals
Change from base Build 9583192592:	-0.2%
Covered Lines:	6722
Relevant Lines:	7471

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9668339128

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.007%) to 89.975%

---

Files with Coverage Reduction	New Missed Lines	%
components/builders/answer_builder.py	1	98.36%

Totals
Change from base Build 9664851641:	0.007%
Covered Lines:	6722
Relevant Lines:	7471

---

💛 - Coveralls

[lbux]

The mypy issues were resolved by explicitly casting as I did not want to just # type: ignore, but it can be done if that is preferred. I was hoping the isinstance check would be enough, but mypy still thinks we are trying to do ChatMessage logic on a string.

[coveralls]

Pull Request Test Coverage Report for Build 9799313838

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 62 unchanged lines in 9 files lost coverage.
• Overall coverage increased (+0.04%) to 90.003%

---

Files with Coverage Reduction	New Missed Lines	%
components/builders/answer_builder.py	1	98.28%
tracing/datadog.py	1	94.59%
components/generators/openai.py	2	96.34%
components/routers/conditional_router.py	2	97.4%
components/audio/whisper_local.py	5	92.19%
components/evaluators/llm_evaluator.py	6	94.74%
components/fetchers/link_content.py	12	78.49%
components/converters/azure.py	14	89.55%
core/pipeline/pipeline.py	19	73.83%

Totals
Change from base Build 9664851641:	0.04%
Covered Lines:	6770
Relevant Lines:	7522

---

💛 - Coveralls

[julian-risch]

Looks good to me now. 👍 Ready to be merged.
Sorry for taking exceptionally long for the review. The only changes I made is that the inputs remain unchanged so we don't overwrite the replies and meta inputs. In addition, I added one type ignore instead of casting and moved the extraction inside of the loop.
Thanks again for contributing to Haystack! 🎉

[julian-risch]

@dfokina For updating the documentation, we need to add here that the AnswerBuilder works not only with Generators but also with ChatGenerators and that the replies input can be either a List[str] or a List[ChatMessage]: https://docs.haystack.deepset.ai/v2.3-unstable/docs/answerbuilder I'll create an issue for that and will assign you. We can sync on the changes and I can support you.