Svelte + Rollup error [!] (plugin commonjs) SyntaxError: Deleting local variable in strict mode (8:8)?

Question

I am building a web app in svelte ( which uses rollup ). I am using a 3rd party SDK which implements this API https://github.com/near/near-api-js . This API imports JSON at some point. Because of this, I had to install @rollup/plugin-json.

I am importing it into my rollup.config.js as follows...

import svelte from 'rollup-plugin-svelte';
import commonjs from '@rollup/plugin-commonjs';
import resolve from '@rollup/plugin-node-resolve';
import livereload from 'rollup-plugin-livereload';
import { terser } from 'rollup-plugin-terser';
import css from 'rollup-plugin-css-only';
import json from '@rollup/plugin-json';

const production = !process.env.ROLLUP_WATCH;

function serve() {
    let server;

    function toExit() {
        if (server) server.kill(0);
    }

    return {
        writeBundle() {
            if (server) return;
            server = require('child_process').spawn('npm', ['run', 'start', '--', '--dev'], {
                stdio: ['ignore', 'inherit', 'inherit'],
                shell: true
            });

            process.on('SIGTERM', toExit);
            process.on('exit', toExit);
        }
    };
}

export default {
    input: 'src/main.js',
    output: {
        sourcemap: true,
        format: 'cjs',
        name: 'app',
        file: 'public/build/bundle.js',
    },
    plugins: [
        svelte({
            compilerOptions: {
                // enable run-time checks when not in production
                dev: !production
            }
        }),
        // we'll extract any component CSS out into
        // a separate file - better for performance
        css({ output: 'bundle.css' }),

        // If you have external dependencies installed from
        // npm, you'll most likely need these plugins. In
        // some cases you'll need additional configuration -
        // consult the documentation for details:
        // https://github.com/rollup/plugins/tree/master/packages/commonjs
        resolve({
            browser: true,
            dedupe: ['svelte']
        }),
        commonjs(),
        json(),

        // In dev mode, call `npm run start` once
        // the bundle has been generated
        !production && serve(),

        // Watch the `public` directory and refresh the
        // browser on changes when not in production
        !production && livereload('public'),

        // If we're building for production (npm run build
        // instead of npm run dev), minify
        production && terser()
    ],
    watch: {
        clearScreen: false
    }
};

From here I am calling the 3rd Party SDK in /Services/FluxProvider.js like this...

• Note : I also tried this in the script tag of App.js... same results when calling one of the SDK methods

 export let name;

  import FluxSdk from "@fluxprotocol/amm-sdk";

  async function main() {
    const sdk = new FluxSdk();
    await sdk.connect();

    console.log("Connected and ready to go!");
  }

  main();

After doing this, I get the following error...

(!) Plugin node-resolve: preferring built-in module 'util' over local alternative at 'C:\Users\Ethan\node_modules\util\util.js', pass 'preferBuiltins: false' to disable this behavior or 'preferBuiltins: true' to disable this warning [!] (plugin commonjs) SyntaxError: Deleting local variable in strict mode (8:8) in C:\Users\Ethan\Desktop\AMM-test\node_modules\u3\lib\cache.js

I have done the following...

1. Had the SDK developer ( not the NEAR API developer, but the SDK that implements the NEAR Api) take a look. He couldn't find the cause.
2. I attempted to rebuild the web app in Svelte-webpack, but that just gave other issues like cannot find 'fs'

I am not sure why this is happening and after asking a few people, they aren't sure either.

IMPORTANT NOTE: This SDK works perfectly fine in my create-react-app project, but not in svelte webpack or svelte rollup.

Any idea's / suggestions welcome.

Answer 1

I tried the same thing with a webpack template

npx degit sveltejs/template-webpack svelte-app

it didn't blare with these errors, I suspect rollup isn't friendly with the fluxsdk packaged with webpack.

With the webpack template, there are no errors and svelte seems to compile just fine.

IMPORTANT NOTE: This SDK works perfectly fine in my create-react-app project, but not in svelte webpack or svelte rollup.

CRA uses webpack too.