Inject metadata into the prompt with createStuffDocumentsChain

[codinginflow]

Any idea why the page_url is not available? According to the documentation of createStuffDocumentsChain, this should automatically be populated from the documents' metadata. And the value definitely exists in the metadata.

const historyAwareCombineDocsChain = await createStuffDocumentsChain({
  llm: streamingModel,
  prompt: ChatPromptTemplate.fromMessages([
    [
      "system",
      `Answer the user's questions based on the below context. When it makes sense, provide a link to the source in markdown format.
      
      Context:
      
      {context}`,
    ],
    new MessagesPlaceholder("chat_history"),
    ["user", "{input}"],
  ]),
  documentPrompt: PromptTemplate.fromTemplate(
    "Source: {page_url}\n\nPage content:\n{page_content}"
  ),
  documentSeparator: "\n------\n",
});

const retriever = (await getVectorStore()).asRetriever();

const historyAwareRetrieverChain = await createHistoryAwareRetriever({
  llm: nonStreamingModel,
  retriever,
  rephrasePrompt: ChatPromptTemplate.fromMessages([
    new MessagesPlaceholder("chat_history"),
    ["user", "{input}"],
    [
      "user",
      "Given the above conversation, generate a search query to look up in order to get information relevant to the conversation",
    ],
  ]),
});

const conversationalRetrievalChain = await createRetrievalChain({
  retriever: historyAwareRetrieverChain,
  combineDocsChain: historyAwareCombineDocsChain,
});

[dosubot[bot]]

🤖

Hello @codinginflow! I'm Dosu, a friendly bot here to assist while we wait for a human maintainer. I can help you solve bugs, answer questions, and guide you to become a contributor. Feel free to ask me anything and I'll do my best to assist.

The page_url is not being populated from the documents' metadata because the documentPrompt parameter in the createStuffDocumentsChain function is set to DEFAULT_DOCUMENT_PROMPT by default. This default prompt only contains Document.page_content.

If you want to include page_url from the document's metadata, you need to pass a custom documentPrompt that includes page_url as an input variable when calling createStuffDocumentsChain.

Here's an example of how you can do this:

import { BasePromptTemplate } from "@langchain/core/prompts";

const customDocumentPrompt = new BasePromptTemplate({
  template: "{page_content} {page_url}",
  inputVariables: ["page_content", "page_url"],
});

createStuffDocumentsChain({
  llm: yourLanguageModel,
  prompt: yourPrompt,
  documentPrompt: customDocumentPrompt,
});

In this example, customDocumentPrompt is a new instance of BasePromptTemplate that includes both page_content and page_url in its template and input variables. This custom prompt is then passed to createStuffDocumentsChain as the documentPrompt parameter.

You can find more details about this in the langchain/src/chains/combine_documents/stuff.ts file in the langchainjs repository.

I hope this helps! If you have any other questions, feel free to ask.

-Dosu

Sources

• langchain/src/chains/combine_documents/stuff.ts

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[codinginflow]

@dosu-bot My code above already contains the custom documentPrompt

[dosubot[bot]]

🤖

It's great to hear that you've already implemented the custom documentPrompt in your code. If you have any further questions or need assistance with anything else related to the langchainjs framework or any other development topic, feel free to ask!

---

This response is meant to be useful and save you time. It is not meant to be a precise solution, but rather a starting point for your own research.

Help me be more useful! Please leave a 👍 if this is helpful and 👎 if it is irrelevant.

If you want to continue the conversation, start your reply with @dosu-bot.