Writing plugin for TS: different results in execution in Rust context or in JS context

[amanteaux]

Hello,

I want to build a plugin that adds metadata on TS classes based on the constructor types. This is for dependency injection, my final goal is to replace the TS transformer https://github.com/wessberg/DI-compiler

I am using the hooks fn visit_mut_class_decl(&mut self, class_decl: &mut ClassDecl) and fn visit_mut_class_expr(&mut self, class_expr: &mut ClassExpr) to get class data.
I am the using this code to extract constructor information:

        for member in &class.body {
            if let ClassMember::Constructor(constructor) = member {
                println!("ClassMember::Constructor");
                for param in &constructor.params {
// [...]

Everything works perfectly when executed in a Rust environment: I correctly get params as a TsParamProp, so I am able to recover the param type.
However, when I execute the plugin from JS, I get params as Param: so the type information seems erased, as if I was getting the JS version of the TS file I want to compile.

Here is my JSC JS parser configuration:

      parser: {
        syntax: "typescript",
        tsx: true,
        decorators: true,
      }

Here are some debug information I get, from Rust execution:

TsParamProp { span: 180..217#0, decorators: [], accessibility: Some(Private), is_override: false, readonly: true, param: Ident(BindingIdent { id: Ident { span: 197..206#0, sym: "sampleApi", optional: false }, type_ann: Some(TsTypeAnn { span: 206..217#0, type_ann: TsTypeRef(TsTypeRef { span: 208..217#0, type_name: Ident(Ident { span: 208..217#0, sym: "SampleApi", optional: false }), type_params: None }) }) }) }

From JS execution (on the same TS file where types seems to be erased):

Param { span: 181..218#0, decorators: [], pat: Ident(BindingIdent { id: Ident { span: 198..207#3, sym: "sampleApi", optional: false }, type_ann: None }) }

I use in JS the @swc/core in version 1.6.6 whereas in Rust I am using swc_core 0.95.10 and swc_ecma_parser 0.146.7.

I feel like I am missing a simple option that would enable me to correctly get the TsParamProp type. But I cannot find it!
Any ideas?

I can provide all my code if necessary.
Thank you for your help!

[kdy1]

TypeScript/decorators are handled before running Wasm plugins. I'll document it.

[kdy1]

See #9132

[amanteaux]

Thank you very much for your quick answer! Having TypeScript transformers would enable to completely remove TSC compilation from our build tools, it would be really awesome!

If I can help in any way to implement #9132, please tell me.