The Problem with Inlay Hints

Oct 13, 2025 by miodeya.com 10 views

Understanding Inlay Hints

Inlay hints are a feature in programming languages that provide additional information about the code being written. They are typically displayed as a small piece of text or a symbol that appears within the code, providing context and helping the developer understand the code better. Inlay hints can be particularly useful when working with complex codebases or when trying to understand the behavior of a specific function or method.

The Problem with Inlay Hints

However, in some cases, inlay hints may not reappear after file edits. This can be frustrating for developers who rely on these hints to understand their code. In this article, we will explore a specific scenario where inlay hints sometimes don't reappear after file edits.

A Simple Example

Let's consider a simple Scala program:

def main() = println("hello world")

After the LSP server loads initially, the following inlay hint gets shown for the inferred io capture:

{io} def main() = println("hello world")

In this example, the inlay hint is displayed as a small piece of text that appears within the code. The hint provides information about the io capture, which is a variable that is inferred by the compiler.

The Issue with Inlay Hints

Now, let's say we enter a blank line above the main function. The hint disappears. This is where the issue arises. The inlay hint is no longer displayed, even though the code has not changed.

Analyzing the LSP Trace

To better understand the issue, let's take a look at the LSP (Language Server Protocol) trace:

[Trace - 11:03:56 AM] Received request 'textDocument/inlayHint - (4)'
[Trace - 11:03:56 AM] Sending response 'textDocument/inlayHint - (4)'. Processing request took 1ms
Result: [
  {
    "position": {
      "line": 0,
      "character": 0
    },
    "label": "{io}",
    "kind": 1,
    "tooltip": {
      "kind": "markdown",
      "value": "captures: `{io}`"
    },
    "paddingLeft": false,
    "paddingRight": true,
    "data": "capture"
  }
[Trace - 11:03:57 AM] Received request 'textDocument/inlayHint - (6)'
[Trace - 11:03:57 AM] Sending response 'textDocument/inlayHint - (6)'. Processing request took 0ms
Result: null

In this LSP trace, we can see that the inlay hint is initially displayed (request 4) and then disappears (request 6). The response to request 6 is null, indicating that the inlay hint is no longer available.

Conclusion

In conclusion, inlay hints sometimes don't reappear after file edits. This can be frustrating for developers who rely on these hints to understand their code. By analyzing the LSP trace, we can see that the inlay hint is initially displayed and then disappears after a file edit. This issue highlights the importance of understanding the behavior of inlay hints and how they are affected by file edits.

Best Practices for Working with Inlay Hints

To avoid issues with inlay hints, follow these best practices:

Understand how inlay hints work: Inlay hints are a feature that provides additional information about the code being written. They are typically displayed as a small piece of text or a symbol that appears within the code.
Use inlay hints judiciously: Inlay hints can be useful for understanding complex codebases or specific functions or methods. However, they should not be relied upon as the sole means of understanding the code.
Be aware of file edits: File edits can affect the availability of inlay hints. Be aware of when file edits occur and how they may impact the availability of inlay hints.
Use the LSP trace to diagnose issues: The LSP trace can provide valuable information about the behavior of inlay hints. Use the LSP trace to diagnose issues and understand how inlay hints are affected by file edits.

Common Issues with Inlay Hints

In addition to the issue described in this article, there are several other common issues with inlay hints:

Inlay hints not appearing: Inlay hints may not appear at all, even when they are available.
Inlay hints disappearing: Inlay hints may disappear after a file edit or when the code is modified.
Inlay hints not updating: Inlay hints may not update when the code is modified or when new information becomes available.

Troubleshooting Inlay Hints

If you are experiencing issues with inlay hints, follow these steps to troubleshoot the issue:

Check the LSP trace: The LSP trace can provide valuable information about the behavior of inlay hints. Check the LSP trace to see if there are any errors or issues that may be affecting the availability of inlay hints.
Verify the code: Verify that the code is correct and that there are no syntax errors or other issues that may be affecting the availability of inlay hints.
Check the inlay hint settings: Check the inlay hint settings to ensure that they are correctly configured and that the inlay hints are enabled.
Restart the LSP server: Restart the LSP server to see if the issue is resolved.

Conclusion

Q: What are inlay hints?

A: Inlay hints are a feature in programming languages that provide additional information about the code being written. They are typically displayed as a small piece of text or a symbol that appears within the code, providing context and helping the developer understand the code better.

Q: Why do inlay hints sometimes not reappear after file edits?

A: Inlay hints may not reappear after file edits due to various reasons, including:

LSP server issues: The LSP server may not be able to retrieve the inlay hint information after a file edit.
Code syntax errors: Syntax errors in the code may prevent the inlay hint from appearing.
Inlay hint settings: The inlay hint settings may not be correctly configured, preventing the inlay hint from appearing.

Q: How can I troubleshoot inlay hint issues?

A: To troubleshoot inlay hint issues, follow these steps:

Check the LSP trace: The LSP trace can provide valuable information about the behavior of inlay hints. Check the LSP trace to see if there are any errors or issues that may be affecting the availability of inlay hints.
Verify the code: Verify that the code is correct and that there are no syntax errors or other issues that may be affecting the availability of inlay hints.
Check the inlay hint settings: Check the inlay hint settings to ensure that they are correctly configured and that the inlay hints are enabled.
Restart the LSP server: Restart the LSP server to see if the issue is resolved.

Q: Can I customize the appearance of inlay hints?

A: Yes, you can customize the appearance of inlay hints. The appearance of inlay hints can be customized through the inlay hint settings.

Q: Are inlay hints available for all programming languages?

A: No, inlay hints are not available for all programming languages. Inlay hints are typically available for languages that support the LSP protocol, such as Java, Python, and C++.

Q: Can I use inlay hints with other development tools?

A: Yes, you can use inlay hints with other development tools, such as IDEs and code editors. Inlay hints can be integrated with other development tools to provide a more comprehensive development experience.

Q: How can I enable inlay hints in my development environment?

A: To enable inlay hints in your development environment, follow these steps:

Check the LSP server settings: Check the LSP server settings to ensure that inlay hints are enabled.
Configure the inlay hint settings: Configure the inlay hint settings to customize the appearance and behavior of inlay hints.
Restart the LSP server: Restart the LSP server to apply the changes.

Q: Can I use inlay hints with other features of the LSP protocol?

A: Yes, you can use inlay hints with other features of the LSP protocol, such as code completion, code refactoring, and code analysis.

Q: Are inlay hints secure?

A: Yes, inlay hints are secure. Inlay hints are designed to provide additional information about the code being written, without compromising the security of the code.

Q: Can I use inlay hints with other development frameworks?

A: Yes, you can use inlay hints with other development frameworks, such as Spring Boot, Django, and React.

Conclusion

In conclusion, inlay hints are a powerful feature of the LSP protocol that can provide additional information about the code being written. By understanding how inlay hints work and following best practices for working with inlay hints, developers can avoid issues with inlay hints and ensure that they are available when needed.