Top level await with SWC

[timneutkens]

Before the launch of SWC by default we opted out the test for top level await as it is still quite experimental. We have to revisit top level await support, e.g. check how it's handled with Babel currently, to make sure it works with SWC.

[ctjlewis]

This is an incredibly important language feature and IMO it has been a mistake to deprioritize it in general and leave it as an experimental opt-in.

Top-level await is one of the only hangups that prevent valid JS programs from being executed inside Next, the others being:

• Next server context isolation (feat(server): isolate component modules #29565)
• Experimental ESM externals

This is currently causing issues trying to import perfectly valid modules that contain top-level await statements, even with the flag enabled (as you mentioned, it's not well-tested).

[djvex]

Yeah I am new to developing with next.js and running into this issue as well.

I'm new to next.js and the JavaScript ecosystem in general.

In my node_modules\next\dist\build\webpack\loaders\next-swc-loader.js file I tried adding exports.experiements.futureDefaults = true. Is even getting my app to compile even possible or am I just stuck waiting for you guys to make an update at this point?

`"use strict";
Object.defineProperty(exports, "__esModule", {
    value: true
});
exports.pitch = pitch;
exports.default = swcLoader;
exports.raw = void 0;
exports.experiments.futureDefaults = true; // I think I need this?
var _swc = require("../../swc");
var _options = require("../../swc/options");
var _path = require("path");
async function loaderTransform(parentTrace, source, inputSourceMap) {
    // Make the loader async
    const filename = this.resourcePath;
    let loaderOptions = this.getOptions() || {

[gabrieli]

Is there any workaround for using top level await with swc until the feature is supported?
Thanks!

[eric-burel]

This seems to prevent Apollo Server setup or at least to make it harder, the open PR to update to Apollo 3 also use a top level await: #30082

[trevex]

I just ran into this issue and worked around it by using babel instead.

Just create a .babelrc, also see docs and babel will be used instead.

[TommySorensen]

There is a topLevelAwait setting in the SWC documentation, does this mean that it's supported in SWC and therefore nextjs? https://swc.rs/docs/configuration/compilation