`LangchainIntegration` breaks if only `langchain-core` is installed

[mshavliuk]

How do you use Sentry?

Sentry Saas (sentry.io)

Version

2.35.1, 2.37.0

Steps to Reproduce

#4678 has introduced changes that made langchain package required to be installed in order to use LangchainIntegration whereas previously only the langchain-core was required. The integration, however, uses langchain package only to wrap the AgentExecutor methods, which is anyway optional.

1. create a project with langchain-core and sentry-sdk packages
2. run sentry_sdk.integrations.langchain
3. See DidNotEnable("langchain not installed") exception

Or just run this command

uv run --with "sentry-sdk" --with "langchain-core" python -c "import sentry_sdk.integrations.langchain"

Expected Result

When langchain package is not installed it just skips wrapping AgentExecutor methods in setup_once if langchain package is not present

Actual Result

Traceback (most recent call last):
  File "/Users/user/.cache/uv/archive-v0/LbXO3QDNdb9rlVPdSE8LR/lib/python3.12/site-packages/sentry_sdk/integrations/langchain.py", line 32, in <module>
    from langchain.agents import AgentExecutor
ModuleNotFoundError: No module named 'langchain'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/user/.cache/uv/archive-v0/LbXO3QDNdb9rlVPdSE8LR/lib/python3.12/site-packages/sentry_sdk/integrations/langchain.py", line 44, in <module>
    raise DidNotEnable("langchain not installed")
sentry_sdk.integrations.DidNotEnable: langchain not installed

[linear]

PY-1833 `LangchainIntegration` breaks if only `langchain-core` is installed

[antonpirker]

Hey @mshavliuk thanks for writing in!

There should definitely not be an error when langchain is not installed like you showed above. We will fix this.

[antonpirker]

@mshavliuk we have a fix: #4783
this will be released soon.