feat(community): Neo4j chat message history

[BernardFaucher]

What? Why?

This PR adds the Neo4jChatMessageHistory class to @langchain/community, in furtherance of reaching functional parity with the Python version of the package. PTAL 👀

Tests?

Yes! A new integration test is added to the corresponding tests folder, covering all the new functionality in well-scoped describe/it blocks, including set-up and tear-down. To facilitate testing, the neo4j service has also been added to test-int-deps-docker-compose.yml, pinned to the latest image. To start the test container, run: docker-compose -f test-int-deps-docker-compose.yml up -d from the project root, then run the test with: yarn run test:single src/stores/tests/neo4j.int.test.ts from the libs/langchain-community workspace. Alternatively, you can test against a neo4j server running locally with Neo4j Desktop, or in the cloud using https://sandbox.neo4j.com/ - all three options are working.

Demo?

Yes! Here's a gif of the test successfully passing:

And here's a png of what a chat message history persisted with Neo4jChatMessageHistory looks like in neo4j:

Considerations?

Where sensible, the defaults and conventions of the python code are maintained. Any divergences are configurable, and represent a holistic view of the js/node ecosystem and coding conventions. Raw Cypher passed to the neo4j driver via the new class is tightened up and idiomatic, without hurting query functionality, and uses the params object over string interpolation as much as possible as a security consideration.

Appreciation?

Twitter is not the place to be, but I'd love a friendly shout out on Mastodon at @[email protected] or mention on my LinkedIn 🙏

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[jacoblee93]

Looks ok overall, will tag in @tomasonjo for a look too though!

[BernardFaucher]

Thanks for the feedback, @jacoblee93 ! I'll run yarn format and switch from the # to the private syntax.
The call to neo4j.driver is, indeed, sync - async initialization is deferred to first driver call. I'm happy to turn it into an IIAFE, exposed from a new class method init if that's what consumers expect. I'll make those changes, and give you and Tomaz a ping when they're in 👍

[BernardFaucher]

Thanks for the review - your requested changes are in, @jacoblee93 🚀
From a Neo4j perspective, what do you think @tomasonjo ? Are there further optimizations I can add?

[BernardFaucher]

cc: @adam-cowley

[tomasonjo]

Can you copy some connection validation and query execution from: https://github.com/langchain-ai/langchainjs/blob/main/libs/langchain-community/src/graphs/neo4j_graph.ts#L312

[BernardFaucher]

Can you copy some connection validation and query execution from: https://github.com/langchain-ai/langchainjs/blob/main/libs/langchain-community/src/graphs/neo4j_graph.ts#L312

Thanks for reviewing @tomasonjo 🙌

To your first ask, I do have a verifyConnection class method that's public, called as part of the initialize factory method, and included in the test suite. Did you have something else in mind for connection validation?

To your second ask, I'd like to make sure I'm understanding you correctly: You'd like the Neo4jChatMessageHistory class to be able to execute arbitrary Cypher queries on the underlying database? It's totally doable, it just seems like something better left to the Neo4jGraph class. If the intention is to avoid two expensive calls to neo4j.driver, an option might be to take an existing instance of a Neo4jGraph as an optional prop in the constructor, adjusting some of the surrounding logic accordingly. I'd considered going that route when first planning the code, but decided against it because of the APOC dependency. Does that sound preferable, or is giving Neo4jChatMessageHistory a query method what you're looking for?

[tomasonjo]

No, no need for arbitrary queries. Just change session run to driver execute query V pet., 13. dec. 2024, 17:02 je oseba Bernard F Faucher < ***@***.***> napisala:

…

Can you copy some connection validation and query execution from: https://github.com/langchain-ai/langchainjs/blob/main/libs/langchain-community/src/graphs/neo4j_graph.ts#L312 Thanks for reviewing @tomasonjo <https://github.com/tomasonjo> 🙌 To your first ask, I do have a verifyConnection <https://github.com/langchain-ai/langchainjs/pull/7331/files#diff-ebd6083757dd12c113f92ca3eca68fb12c389133b082cc391f8f3924db3edc59R85-R88> class method that's public, called as part of the initialize <https://github.com/langchain-ai/langchainjs/pull/7331/files#diff-ebd6083757dd12c113f92ca3eca68fb12c389133b082cc391f8f3924db3edc59R71-R80> factory method, and included in the test suite <https://github.com/langchain-ai/langchainjs/pull/7331/files#diff-8ed0e6b3000d381fba19719b0e57b2e71e98a78a13ee24d9be2f21b1a32a954cR74-R77>. Did you have something else in mind for connection validation? To your second ask, I'd like to make sure I'm understanding you correctly: You'd like the Neo4jChatMessageHistory class to be able to execute arbitrary Cypher queries on the underlying database? It's totally doable, it just seems like something better left to the Neo4jGraph class. If the intention is to avoid two expensive calls to neo4j.driver, an option might be to take an existing instance of a Neo4jGraph as an optional prop in the constructor, adjusting some of the surrounding logic accordingly. I'd considered going that route when first planning the code, but decided against it because of the APOC dependency. Does that sound preferable, or is giving Neo4jChatMessageHistory a query method what you're looking for? — Reply to this email directly, view it on GitHub <#7331 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEYGGTOTUEDDVBJXESJBTUD2FMALBAVCNFSM6AAAAABTG66EK2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDKNBRG43DKOBTGM> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[BernardFaucher]

I understand - thanks for clarifying! I'll get right on it 💨

[BernardFaucher]

@tomasonjo Your requested changes are in & all tests are green ✅
@jacoblee93 I'm satisfied with this feature - would you like anything else before 🚢?

[jacoblee93]

Thank you!

[jacoblee93]

Neo4jError seems to take an additional argument for code, just switched to native error