Скачать или смотреть Solving the TypeScript Compiler API Issue: Creating a Transformer for Node Replacement

Learn how to effectively use the TypeScript Compiler API to ensure node transformations persist in emitted files when creating a custom transformer.
---
This video is based on the question https://stackoverflow.com/q/68943590/ asked by the user 'Daniel de Andrade Varela' ( https://stackoverflow.com/u/4738367/ ) and on the answer https://stackoverflow.com/a/68943928/ provided by the user 'David Sherret' ( https://stackoverflow.com/u/188246/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: TypeScript Compiler API: how to create a transformer that's replace a node when emit files

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Solving the TypeScript Compiler API Issue: Creating a Transformer for Node Replacement

When working with the TypeScript Compiler API, you may encounter challenges when trying to transform nodes while ensuring that those transformations persist in your emitted files. A common task can be appending a suffix to every node identifier or making similar changes. In this guide, we will dive into how to effectively create a transformer that not only transforms the identifiers in your code but also ensures these changes get reflected in the emitted output.

The Problem

Here, we’ll look at a sample implementation where a transformer is meant to append a suffix to each identifier in a TypeScript file. The code snippet provided works effectively for logging the transformed content in the console but doesn't reflect these changes in the emitted JavaScript file.

Consider the input file source.ts with the following content:

[[See Video to Reveal this Text or Code Snippet]]

When processed, the console output produces the correctly transformed result:

[[See Video to Reveal this Text or Code Snippet]]

However, looking at the emitted output in source.js, we still see:

[[See Video to Reveal this Text or Code Snippet]]

This discrepancy is where our focus lies - ensuring that the changes made by the transformer are retained in the file that gets emitted.

Solution Breakdown

To solve the problem, let's break down the required steps to ensure the transformer is activated during the emit process and the node transformations persist.

Step 1: Understanding the Transform and Print Process

The key issue here is that while you successfully transform your identifiers, this transformation doesn't take place during the emit phase. The product of the transform and print process should actually integrate into the TypeScript compiler's emission pipeline.

Step 2: Modify the Emit Process

Instead of merely transforming the nodes and printing them, the transformer factory needs to be provided to the emit method of the program. Here’s how you can correctly implement that:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Implementing the Changes

By modifying the emit process, we effectively inform the TypeScript compiler to use our custom transformer before the emission occurs. This ensures that every transformation made gets incorporated into the emitted output.

Complete Example

Bringing together all the above ideas, your complete code should look like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following these steps, you can ensure that your TypeScript transformations are not only visible in the console output but are also reflected in the emitted files. This ability to manipulate nodes and guarantee their persistence in the final output is vital for effective TypeScript development.

Now, go ahead and implement this method in your projects, and watch your TypeScript transformations thrive!