Fixing TypeError: M.content.find Is Not A Function In Genkit

by SLV Team 61 views

Hey guys! Running into that frustrating TypeError: m.content.find is not a function when you're trying to use multi-turn messages with Genkit? Yeah, it's a pain, but let's break down what's causing it and how to fix it.

Understanding the Issue

So, what's happening? The error message TypeError: m.content.find is not a function basically means that you're trying to call the .find() method on something that isn't an array or doesn't have that method available. In the context of the provided code and the Genkit library, it looks like the content property of a message (m.content) is sometimes undefined or not an array when the code expects it to be. This usually happens when the structure of the message object isn't what the applyResources function anticipates.

The problematic line is:

rawRequest.messages.find((m) => !!m.content.find((c) => c.resource))

Here, the code assumes that every message m in rawRequest.messages has a content property, and that this content property is an array that can be searched using .find(). When content is undefined or not an array, .find() will throw that TypeError.

Why does this happen?

This issue often arises due to inconsistent message structures, especially in multi-turn conversations where different messages might have different formats or content types. For instance, some messages might only contain text, while others might include media, data, or resources. If the content field is not consistently populated as an array, the applyResources function will fail.

Debugging Steps

  1. Inspect the Messages:

    • Log the structure of rawRequest.messages to the console before the .find() call. This will help you see exactly what the messages look like and identify any messages where content is missing or not an array.
    • Example: console.log(JSON.stringify(rawRequest.messages, null, 2));
  2. Check Message Construction:

    • Examine the code that constructs the messages, particularly the addMessage function. Ensure that the content property is always an array, even if it's an empty array.
    • Example: Make sure that when you add a message, the content is structured correctly:
      const addMessage = (sessionId: string, message: any) => {
          const messages = sessions[sessionId] || [];
          // Ensure content is always an array
          if (!Array.isArray(message.content)) {
              message.content = [message.content]; // Wrap content in an array if it's not already
          }
          messages.push(message);
          sessions[sessionId] = messages;
          return messages;
      };
      

Solution: Safely Check and Handle content

To resolve this, you need to add a check to ensure that m.content exists and is an array before attempting to call .find() on it. Here’s how you can modify the code:

rawRequest.messages.find(m => m.content && Array.isArray(m.content) && m.content.find(c => c.resource))

Explanation:

  • m.content &&: This checks if m.content exists and is not null or undefined. If it doesn't exist, the expression short-circuits and avoids the error.
  • Array.isArray(m.content) &&: This verifies that m.content is indeed an array before attempting to use .find() on it. If it's not an array, the expression short-circuits as well.
  • m.content.find(c => c.resource): This is the original .find() call, but it's only executed if both of the above conditions are met.

Implementing the Fix

Here’s how you can apply this fix in the applyResources function:

async function applyResources(registry, rawRequest, resources) {
  if (!rawRequest.messages.find(m => m.content && Array.isArray(m.content) && m.content.find(c => c.resource))) {
    // ... rest of your code
  }
}

By adding this check, you ensure that you only attempt to call .find() on m.content when it is actually an array, preventing the TypeError.

Complete Example

Here’s a more robust version of the chatWithAI function with the fix and additional safety checks:

const ai = genkit({
    plugins: [
        googleAI({
            apiKey: GEMINI_API_KEY,
        }),
    ],
    model: googleAI.model("gemini-2.5-flash"),
    name: "my-ai",
});

const sessions: Record<string, any[]> = {};

const addMessage = (sessionId: string, message: any) => {
    const messages = sessions[sessionId] || [];
    // Ensure content is always an array
    if (!Array.isArray(message.content)) {
        message.content = [message.content]; // Wrap content in an array if it's not already
    }
    messages.push(message);
    sessions[sessionId] = messages;
    return messages;
};

export async function chatWithAI(
    sessionId: string,
    prompt: string,
    context: string,
) {
    const oldMessages = addMessage(sessionId, {
        role: "user",
        content: prompt,
    });

    try {
        const response = await ai.generate({
            system: systemPrompt(context),
            messages: oldMessages,
        });
        addMessage(sessionId, {
            role: "model",
            content: response.text,
        });

        return response.text;
    } catch (error) {
        console.error("Error during AI generation:", error);
        return "Sorry, I encountered an error.";
    }
}

// example

chatWithAI(
    "123",
    "What is the summary of the website?",
    "Lovely shoes and clothes store.",
);

Additional Tips for Robustness

  1. Validate Message Structure:

    • Consider adding a validation step to ensure that all messages conform to a specific schema. This can help catch issues early and provide more informative error messages.
  2. Defensive Programming:

    • Always check if variables are defined before using them, especially when dealing with external data or user inputs.
  3. Error Handling:

    • Wrap your ai.generate call in a try...catch block to handle any errors that might occur during the AI generation process. This prevents your application from crashing and allows you to provide a graceful fallback.

Conclusion

By ensuring that m.content is always an array and adding checks before calling .find(), you can avoid the TypeError and make your Genkit application more robust. Always validate your data and handle potential errors gracefully to create a smoother user experience. Happy coding, and let me know if you run into any other snags!