swc-plugin-source-tracker

SWC plugin that injects data-source attributes into JSX DOM elements at compile time.

Each attribute contains the file path, line number, and column where the element was defined in source code.

<!-- Before -->
<div className="card">
  <h2>Title</h2>
  <p>Content</p>
</div>

<!-- After -->
<div className="card" data-source="app/page.tsx:12:5">
  <h2 data-source="app/page.tsx:13:7">Title</h2>
  <p data-source="app/page.tsx:14:7">Content</p>
</div>

Why?

React 19 removed fiber._debugSource, breaking all click-to-source tools (react-dev-inspector, LocatorJS, click-to-component, etc.).

This plugin provides a build-time alternative that works with Next.js 15, 16, Turbopack, and standalone @swc/core.

Install

npm install swc-plugin-source-tracker

Usage with Next.js

// next.config.mjs
import { withSourceTracker } from "swc-plugin-source-tracker";

const nextConfig = {
  experimental: {
    swcPlugins: [withSourceTracker()],
  },
};

export default nextConfig;

That's it. The plugin auto-detects your Next.js version and selects the compatible WASM binary.

Dev-only

You probably want this in development only:

// next.config.mjs
import { withSourceTracker } from "swc-plugin-source-tracker";

const nextConfig = {
  experimental: {
    swcPlugins: [
      ...(process.env.NODE_ENV === "development" ? [withSourceTracker()] : []),
    ],
  },
};

export default nextConfig;

Options

withSourceTracker(
  // Plugin config (passed to SWC)
  { attr: "data-source" },    // Custom attribute name (default: "data-source")

  // JS options
  { version: "v54" },         // Force specific swc_core version: "v35" | "v54"
);

Usage with @swc/core (standalone)

import { getWasmPath } from "swc-plugin-source-tracker";

const result = await swc.transform(code, {
  filename: "src/App.tsx",
  jsc: {
    parser: { syntax: "typescript", tsx: true },
    experimental: {
      plugins: [[getWasmPath(), {}]],
    },
  },
});

Compatibility

| WASM | swc_core | Next.js | Bundler | |------|----------|---------|---------| | v35 | 35.0.0 | 15.x | Webpack | | v54 | 54.0.0 | 16.x | Turbopack |

withSourceTracker() auto-selects the correct version based on your installed Next.js.

How it works

1. An SWC WASM plugin visits every JSX opening element during compilation
2. For intrinsic DOM elements (div, span, button, etc.), it injects a data-source attribute
3. The value contains filename:line:column resolved from SWC's source map
4. Custom components (<MyComponent>) are skipped — they render DOM elements that get annotated

Reading source info at runtime

Open DevTools and inspect any element to see its data-source attribute, or:

// Paste in browser console
document.addEventListener("click", (e) => {
  const src =
    e.target.getAttribute("data-source") ||
    e.target.closest("[data-source]")?.getAttribute("data-source");
  if (src) console.log(e.target.tagName, "→", src);
}, true);

.gitignore

The plugin copies a WASM file to your project root for Turbopack compatibility. Add this to .gitignore:

swc_plugin_source_tracker.wasm

License

MIT