webpack.config.js is not updated

When upgrading from beta2 to SNAPSHOT, you would expect #5456 to be fixed and the built artifact to be named something else than index.js. This is not the case, it is still index.js. Only if you for some reason happen to delete the autogenerated webpack.config.js, then the artifact is renamed.

As a user, I would expect the autogenerated config to be updated by a new autogenerated config, whenever it changes.

[Legioth]

I’ll elaborate the practicalities of my vision from #5464 since it’s slightly vaguely.

My core idea is that the generated file could have the same contents as today, and then by default the user-owned file would look something like this:

/* A comment that describes the purpose of this structure */
const flowDefaults = require('./some/location/generated-webpack.config.js');
module.exports = flowDefaults;

The magic comes from how the user can modify flowDefaults before exporting anything. Some examples. Please note the explicit checks to verify that the original structure is as expected. This is something that we cannot force users to do, but we can show good example in any documentation that we write.

const flowDefaults = require('./some/location/generated-webpack.config.js');

// Add a custom plugin
flowDefaults.plugins.push(new MyPlugin());

// Update the rules to also transpile `.mjs` files
if (!flowDefaults.module.rules[0].test) {
  throw "Unexpected structure in generated webpack config";
}
flowDefaults.module.rules[0].test = /\.m?js$/

// Include a custom JS in the entry point in addition to generated-flow-imports.js
if (typeof flowDefaults.entry.index != "string") {
  throw "Unexpected structure in generated webpack config";
}
flowDefaults.entry.index = [flowDefaults.entry.index, "myCustomFile.js"];

module.exports = flowDefaults;

[t-gergely]

if (typeof flowDefaults.entry.index != “string”) { throw “Unexpected structure in generated webpack config”; }

I tried that based on the current webpack.config.js and it DOES throw. Then what? I hacked it to

if (typeof flowDefaults.entry.bundle != "string") {
  throw "Unexpected structure in generated webpack config";
}
flowDefaults.entry.bundle = [flowDefaults.entry.bundle, require('path').resolve(__dirname, 'myCustomFile.js')];

but that template should be fixed.