How do I get the "raw" source code of an AST node in a plugin?

[ole-treichel]

I am trying to implement something similiar to this babel plugin as swc-plugin. You can configure a component that will receive the raw, uncompiled JSX markup of its children as a prop, e.g.:

Input:

<Demo>
  <Button>Hello</Button>
</Demo>

Output:

<Demo code={`<Button>Hello</Button>`}>
  <Button>Hello</Button>
</Demo>

I noticed that every AST-node has a span field, but I am unsure how I would use this to get to the corresponding source code.

I am wondering if this is possible at all, maybe I am misunderstanding what the span field is for

[kwonoj]

You may able to try few interfaces around SourceMapper, like https://github.com/swc-project/swc/blob/main/crates/swc_plugin_proxy/src/source_map/plugin_source_map_proxy.rs#L175=

[ole-treichel]

Yepp that works, thanks 👍 .

One follow up question (Hope this is okay):

I see that the PluginSourceMapProxy is only implemented for the wasm32 target. If I understand correctly, swc_ecma_transforms_testing tests plugins without compiling them to wasm. Is there a way to use swc_ecma_transforms_testing in a way that uses the plugin compiled to wasm or supports PluginSourceMapProxy in any other way?

[kwonoj]

you need / should use SourceMap for the non plugin context instead of plugin proxy. That's the reason plugin passes trait SourceMapper instead of implementation to allow to pass correct implementation depends on the context.