doesn't work with ESM packages

[szamanr]

i have a package which uses ES modules, with "type": "module", in my package.json. if i remove that line, the build process completes successfully¹. however, if i keep it, it seems like the es module is not recognised because i get this error:

failed to load config from /foo/vite.config.js
error during build:
/foo/node_modules/vite-dts/dist/esm/plugin.js:1
import loadJSON from 'load-json-file';
^^^^^^

SyntaxError: Cannot use import statement outside a module

not sure if this is an issue with the plugin, or something wrong with my setup. here's my vite.config.js:

// @ts-check
import { defineConfig } from "vite";
import dts from "vite-dts";
import react from "@vitejs/plugin-react";

export default defineConfig({
  build: {
    lib: {
      entry: "src/index.ts",
      // fileName: (format) => `index.${format}.js`,
      formats: ["es", "cjs"],
      // name: "index.js",
    },
    rollupOptions: {
      // externalize deps that shouldn't be bundled
      // into your library
      external: ["react", "react-dom"],
      output: {
        // Provide global variables to use in the UMD build
        // for externalized deps
        globals: {
          react: "React",
        },
        // Since we publish our ./src folder, there's no point
        // in bloating sourcemaps with another copy of it.
        sourcemapExcludeSources: true,
      },
    },
    sourcemap: true,
    target: "esnext",
    minify: false,
  },
  plugins: [dts(), react()],
});

¹ the process completes successfully, but the type definition files are not actually generated, i suspect it's related to #5.