RunnablePassthrough().pick() not working as expected

[LeoAnt02]

Checked other resources

• [X] I added a very descriptive title to this issue.
• [X] I searched the LangChain documentation with the integrated search.
• [X] I used the GitHub search to find a similar question and didn't find it.
• [X] I am sure that this is a bug in LangChain rather than my code.
• [X] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

Example Code

const chain = RunnableSequence.from([
        {
          context: retriever.pipe(formatDocumentsAsString),
          input: new RunnablePassthrough().pick("input"),
        },
        generalPrompt,
        ollama,
        new StringOutputParser(),
      ]);

const stream = await chain.stream({ input: lastUserMessage, chat_history: history });

Error Message and Stack Trace (if applicable)

Failed to process the request text.replace is not a function { "stack": "TypeError: text.replace is not a function\n at OpenAIEmbeddings.embedQuery

Description

I want to select a specific input from my .invoke or .stream in the RunnableSequence

• When using pick, the entire argument is being passthrough

as if I did

const chain = RunnableSequence.from([
        {
          context: retriever.pipe(formatDocumentsAsString),
          input: new RunnablePassthrough(),
        },
        generalPrompt,
        ollama,
        new StringOutputParser(),
      ]);

const stream = await chain.stream({ input: lastUserMessage, chat_history: history });

System Info

typescript, "langchain": "^0.1.37",

[LeoAnt02]

Seems like the solution is this

new RunnablePassthrough().pick(["input"])

takes an array of string instead of a direct string