TypeScript declarations should generate `MainModule` type name based on user inputs

[jnickg]

Currently, users generating TypeScript declarations as part of compilation always get a file where the wasm module's main type is named MainModule. One consequence of this is that users generating packages directly from the TSD and wasm/js output wind up with name collisions, if they import multiple modules into another project. Working around this is not difficult (shown below) but it does betray the fact that, at the time of writing, wasm module type names are hard-coded to be MainModule.

import { MainModule as MyModule1 } from "my-package-1"; // Must use "as" to prevent name collision
import { MainModule as MyModule2 } from "my-package-2";

Further, users can specify names using -s EXPORT_NAME=MyModule (though this isn't always 1:1 with what we'd want to call the module's type), so having an output type name of MainModule can be confusing to users.

Per a conversation in #21460, and #20296, align TSD generation with EXPORT_NAME or a new setting e.g. MODULE_NAME, so that users can set this name automatically.

[sbc100]

Since this type is already encapsulated within the module perhaps its OK for the names to collide?

FWIW I reallly don't like MainModule as a name, but that is a different issue.

Presumably it might even be useful to have them all called the same thing if you are working with multiple modules.

If we do decide that unique names within the module are a good idea how about using the -o filename as the default?

e.g. ./emcc -o foo.js would default to EXPORT_NAME or foo?

Also, is this issue a duplicate of #20952?

[skywalker212]

Can I work on this issue?

[brendandahl]

Sure, though I think this is less of an issue now. With modularize enabled, the export will be a default so the name doesn't really matter e.g. export default function MainModuleFactory .

[skywalker212]

Thanks, I want to start contributing to emscripten, so I will use this as a starting point!

[skywalker212]

Sure, though I think this is less of an issue now. With modularize enabled, the export will be a default so the name doesn't really matter e.g. export default function MainModuleFactory .

I understand what you meant now, I was thinking EXPORT_NAME is used in the name of the interface of the module instead of the name of the factory function that creates the module. As you mentioned, in this case there is no point in changing the export name.