LLMGraphTransformer.convertToGraphDocuments function fails sometimes when prompt chain to fetch nodes and relationships returns null or missing data about langchainjs HOT 1 CLOSED

To address the issues you're encountering with LLMGraphTransformer in LangChain.js, let's tackle them specifically:

For the first issue where you encounter TypeError: Cannot read properties of null (reading 'nodes'), the problem arises when the rawSchema returned by the language model is null or lacks the expected properties. Implementing optional chaining (?.) for accessing rawSchema.nodes and rawSchema.relationships is an effective way to prevent this error. This adjustment ensures your code gracefully handles cases where the expected data structure is not returned.

Regarding the second issue, the error TypeError: Cannot read properties of undefined (reading 'split') indicates an operation on an undefined variable. To mitigate this, providing a fallback value for potentially undefined properties like targetNodeType can prevent the error. It's crucial to choose a fallback that makes sense in your context, ensuring that operations like split can be performed safely.

Here's a quick example of how you might implement these solutions:

// For handling missing nodes and relationships safely
let nodes = rawSchema?.nodes ? rawSchema.nodes.map(mapToBaseNode) : [];
let relationships = rawSchema?.relationships ? rawSchema.relationships.map(mapToBaseRelationship) : [];

// For providing a fallback value when a property is undefined
let targetNodeType = someObject.targetNodeType || "DefaultType"; // Replace "DefaultType" with a sensible default

These adjustments should help you avoid the errors you've been experiencing by ensuring your code does not assume the presence of certain properties and handles missing data gracefully.

Sources

• libs/langchain-community/src/experimental/graph_transformers/llm.int.test.ts
• libs/langchain-community/src/experimental/graph_transformers/llm.ts

from langchainjs.