70 %

Replacing ImportDecl names with SWC's Fold trait

As part of Toast I needed to port a babel plugin that included rewriting some imports from one target to another. This is a simple version of the transformation I needed to make happed in a JS file:

import Thing from "preact";

import Thing from "not-preact";

Here's the code I used to do it in Rust

swc_import_map_rewrite.rs

rust

use std::path::Path;
use string_cache::Atom;
use swc_ecma_ast::{ImportDecl, Str};
use swc_ecma_visit::{noop_fold_type, Fold};

pub struct SWCImportMapRewrite<'a> {
    pub import_map: &'a Path,
}

impl Fold for SWCImportMapRewrite<'_> {
    noop_fold_type!();

    fn fold_import_decl(
        &mut self,
        imports: ImportDecl,
    ) -> ImportDecl {
        ImportDecl {
            src: Str {
                value: Atom::from("not-preact"),
                ..imports.src
            },
            ..imports
        }
    }
}

somewhere_else.rs

rust

program.fold_with(&mut SWCImportMapRewrite {
    import_map: Path::new("thing"),
})