🐛 Bug Report: Edge Data Type Can Be Undefined But Node Data Cannot

Introduction

In this article, we will discuss a bug report related to React Flow, specifically the inconsistency between Node and Edge types when it comes to data types. We will explore the issue, provide a live code example, and discuss the expected behavior.

What Platform Were You Using When You Found the Bug?

• React Flow / Svelte Flow version: @xyflow/react: ^12.4.2
• Browser and version: Not specified
• OS and version: Not specified

Live Code Example

Unfortunately, the live code example is not provided in the bug report.

Describe the Bug

The bug report highlights an inconsistency between Node and Edge types when working with React Flow. In Node, the data field is always required, so it is safe to access properties like data.hostname. However, in Edge, the data field is optional (data?: T), which means that when accessing properties like data.isActive, TypeScript complains that data may be undefined.

This forces the developer to add extra checks (data?.isActive ?? false) while in Node, they can use data.hostname directly without any issues.

Steps to Reproduce the Bug or Issue

My Use Case

Custom Node (Works Fine)

// CustomNode.tsx
export type CustomNodeType = Node<{ hostname: string }, 'node'>;

export const CustomNode = ({ data }: NodeProps<CustomNodeType>) => {
  return <div>{data.hostname}</div>; // ✅ No TypeScript error
};

In this example, the data field is guaranteed to exist, so data.hostname is accessible without additional checks.

Custom Edge (Type Error)

// SimpleFloatingEdge.tsx
export type SimpleFloatingEdgeType = Edge<{ isActive: boolean; isThreat: boolean }, 'floating'>;

export const SimpleFloatingEdge = ({ data }: EdgeProps<SimpleFloatingEdgeType>) => {
  return <div>{data.isActive ? 'Active' : 'Inactive'}</div>; // ❌ TypeScript error: Property 'isActive' does not exist on type '{ isActive: boolean; isThreat: boolean; } | undefined'
};

In this example, since Edge has data?: T, TypeScript expects data to be undefined sometimes. This forces the developer to modify the code to:

// SimpleFloatingEdge.tsx
const isActive = data?.isActive ?? false;

even though they always provide data in their application.

Expected Behavior

Edge should also enforce data as required.

Screenshots or Videos

Unfortunately, no screenshots or videos are provided in the bug report.

Additional Context

The code is traced to the following locations:

• https://github.com/xyflow/xyflow/blob/main/packages/react/src/types/nodes.ts#L13C1-L21C3
• https://github.com/xyflow/xyflow/blob/main/packages/react/src/types/edges.ts#L39

Question

Is there a reason why Edge allows data to be undefined, while Node does not? Would it make sense to enforce data for Edge, or provide an option to do so?

Conclusion

In conclusion, the bug report highlights an inconsistency between Node and Edge types when working with React Flow. The expected behavior is for Edge to also enforce data as required. The developer is forced to add extra checks to access properties like data.isActive due to the optional nature of data in Edge. The root cause of the issue is traced to the code in the nodes.ts and edges.ts files.

Recommendations

Based on the bug report, the following recommendations can be made:

1. Enforce data as required in Edge: This would ensure that data is always available and can be accessed without additional checks.
2. Provide an option to enforce data in Edge: This would give developers the flexibility to choose whether to enforce data as required or not.
3. Update the code in nodes.ts and edges.ts files: The code in these files should be updated to reflect the expected behavior of Edge.

Q: What is the issue with Edge data type in React Flow?

A: The issue is that Edge data type is optional (data?: T), which means that when accessing properties like data.isActive, TypeScript complains that data may be undefined. This forces developers to add extra checks (data?.isActive ?? false) while in Node, they can use data.hostname directly without any issues.

Q: Why is Edge data type optional while Node data type is not?

A: The reason for this inconsistency is not explicitly stated in the bug report. However, it is possible that the developers of React Flow intended for Edge to be more flexible and allow for optional data, while Node is more rigid and requires data to be present.

Q: What are the implications of this issue?

A: The implications of this issue are that developers working with React Flow may need to add extra checks to access properties like data.isActive, which can make their code more complex and harder to maintain. Additionally, this issue may lead to errors and bugs if developers forget to add these checks.

Q: How can this issue be resolved?

A: There are several ways to resolve this issue:

1. Enforce data as required in Edge: This would ensure that data is always available and can be accessed without additional checks.
2. Provide an option to enforce data in Edge: This would give developers the flexibility to choose whether to enforce data as required or not.
3. Update the code in nodes.ts and edges.ts files: The code in these files should be updated to reflect the expected behavior of Edge.

Q: What are the benefits of resolving this issue?

A: The benefits of resolving this issue are:

1. Simplified code: By enforcing data as required in Edge, developers can simplify their code and avoid adding extra checks.
2. Improved maintainability: Resolving this issue can improve the maintainability of code by reducing the complexity and making it easier to understand.
3. Reduced errors and bugs: By ensuring that data is always available, developers can reduce the likelihood of errors and bugs.

Q: How can developers work around this issue?

A: While waiting for the issue to be resolved, developers can work around it by:

1. Adding extra checks: Developers can add extra checks to access properties like data.isActive, such as data?.isActive ?? false.
2. Using optional chaining: Developers can use optional chaining (?.) to access properties like data.isActive, such as data?.isActive.
3. Using default values: Developers can use default values to provide a fallback value when data is undefined.

Q: What is the status of this issue?

A: The status of this issue is not explicitly stated in the bug report. However, it is possible that the developers of React Flow are aware of the issue and are working to resolve it.

Q: How can developers contribute to resolving this issue?

A: Developers can contribute to resolving this issue by:

1. Reporting the issue: Developers can report the issue to the developers of React Flow.
2. Providing feedback: Developers can provide feedback on the issue and suggest possible solutions.
3. Contributing code: Developers can contribute code to resolve the issue.

By working together, developers can help resolve this issue and improve the React Flow library.