Understanding Backtick Escapes

Oct 13, 2025 by wbrum.org 59 views

Introduction

When working with TypeScript, it's essential to understand how exports are handled, especially when dealing with complex data types like Discriminated Unions (DU). In this article, we'll explore a specific issue related to backtick escapes in DU cases and how it affects the generated code.

The Problem

When using a backtick in a DU like type LangCode = | ``pt-Br`` | ``pt-PT```, a function like export function LangCode_pt-Br() {` is generated, causing a syntax error due to the unescaped hyphen. This issue arises because the backtick escape is not properly sanitized, leading to incorrect code generation.

Understanding Backtick Escapes

Backtick escapes are used to escape special characters within a string. In the context of DU cases, they are used to create a new type by combining existing types. However, when a backtick is used within a DU case, it can lead to unexpected behavior.

Example Use Case

Let's consider an example where we define a DU type LangCode with two cases: pt-Br and pt-PT. We want to create a function LangCode_pt-Br() that returns a specific value for the pt-Br case.

type LangCode = | ``pt-Br`` | ``pt-PT``;

export function LangCode_pt-Br(): string {
  return 'pt-Br';
}

Generated Code

When we run the code, the generated code will look something like this:

export function LangCode_pt-Br(): string {
  return 'pt-Br';
}

As you can see, the backtick escape is not properly sanitized, leading to a syntax error due to the unescaped hyphen.

Solution

To fix this issue, we need to properly sanitize the backtick escape. One way to do this is by using a string literal type to define the DU case.

type LangCode = | 'pt-Br' | 'pt-PT';

export function LangCode_pt-Br(): string {
  return 'pt-Br';
}

By using a string literal type, we can avoid the backtick escape issue and generate correct code.

Conclusion

In conclusion, when working with TypeScript and DU cases, it's essential to understand how backtick escapes are handled. By properly sanitizing the backtick escape, we can avoid syntax errors and generate correct code. Remember to use string literal types to define DU cases and avoid using backticks within DU cases.

Best Practices

To avoid this issue in the future, follow these best practices:

Use string literal types to define DU cases.
Avoid using backticks within DU cases.
Properly sanitize backtick escapes when using them within DU cases.

By following these best practices, you can ensure that your code is correct and free from syntax errors.

Common Pitfalls

When working with DU cases and backtick escapes, be aware of the following common pitfalls:

Using backticks within DU cases can lead to syntax errors.
Failing to properly sanitize backtick escapes can result in incorrect code generation.
Not using string literal types to define DU cases can lead to unexpected behavior.

By being aware of these common pitfalls, you can avoid them and write correct code.

Conclusion

Q: What is the issue with backtick escapes in DU cases?

A: The issue arises when a backtick is used within a DU case, causing a syntax error due to the unescaped hyphen. This is because the backtick escape is not properly sanitized, leading to incorrect code generation.

Q: What is a Discriminated Union (DU)?

A: A Discriminated Union (DU) is a type that combines multiple types using a common property. It's a way to define a type that can have multiple possible values, each with its own set of properties.

Q: How do I define a DU case with a backtick escape?

A: You can define a DU case with a backtick escape using the following syntax:

type LangCode = | ``pt-Br`` | ``pt-PT``;

However, this will lead to a syntax error due to the unescaped hyphen.

Q: How do I properly sanitize the backtick escape?

A: To properly sanitize the backtick escape, you can use a string literal type to define the DU case:

type LangCode = | 'pt-Br' | 'pt-PT';

This will avoid the syntax error and generate correct code.

Q: What are some best practices for working with DU cases and backtick escapes?

A: Here are some best practices to keep in mind:

Use string literal types to define DU cases.
Avoid using backticks within DU cases.
Properly sanitize backtick escapes when using them within DU cases.

Q: What are some common pitfalls to avoid when working with DU cases and backtick escapes?

A: Here are some common pitfalls to avoid:

Using backticks within DU cases can lead to syntax errors.
Failing to properly sanitize backtick escapes can result in incorrect code generation.
Not using string literal types to define DU cases can lead to unexpected behavior.

Q: How do I troubleshoot issues with backtick escapes in DU cases?

A: To troubleshoot issues with backtick escapes in DU cases, follow these steps:

Check the syntax of your DU case definition.
Verify that you're using a string literal type to define the DU case.
Ensure that you're properly sanitizing backtick escapes when using them within DU cases.

Q: Can you provide an example of how to use a string literal type to define a DU case?

A: Here's an example of how to use a string literal type to define a DU case:

type LangCode = | 'pt-Br' | 'pt-PT';

export function LangCode_pt-Br(): string {
  return 'pt-Br';
}

This will generate correct code and avoid syntax errors.

Q: How do I know if I'm using a string literal type correctly?

A: To ensure that you're using a string literal type correctly, follow these steps:

Check that you're using the | symbol to define the DU case.
Verify that you're using a string literal type (e.g. 'pt-Br') to define each case.
Ensure that you're not using backticks within the DU case definition.

By following these best practices and troubleshooting tips, you can avoid issues with backtick escapes in DU cases and write correct and efficient code.