Expose pendingRequests

[KaelWD]

Feature Use Case

I'm writing a plugin that needs to make modifications to a file based on other files in the project. In vite I'm using the transform hook with server._pendingRequests to check if I'm the only module left, but there's nothing like this exposed in rollup.

Feature Proposal

Something similar to vite: https://github.com/vitejs/vite/blob/b625a2cf3730fda94d934b23bcec0c859bfa0b24/packages/vite/src/node/server/transformRequest.ts#L49-L52

ModuleLoader:

+    public pendingRequests = new Map()
     async fetchModule({ id, meta, moduleSideEffects, syntheticNamedExports }, importer, isEntry) {
...
         this.graph.watchFiles[id] = true;
-        await this.addModuleSource(id, importer, module);
+        const promise = this.addModuleSource(id, importer, module)
+        this.pendingRequests.set(id, promise.then(() => module))
+        await promise;
+        this.pendingRequests.delete(id)
         const resolveStaticDependencyPromises = this.getResolveStaticDependencyPromises(module)

PluginContext:

    const context = {
+       pendingRequests: graph.moduleLoader.pendingRequests,
        addWatchFile(id) {

[lukastaegert]

While you do not have this exact API, you can already do something similar with a combination of this.load and this.getModuleIds.

The id of a module is added to this.getModuleIds() before its load hook is even run, so all "pending" modules can be found here. When you have the id, you can await this.load(id) to wait until it is loaded and get its module info.

[KaelWD]

That seems to work, thanks! I did still need a timeout too though because this.load(id) sometimes resolves instantly but module.code is still null, so I'd end up in an infinite loop.

[lukastaegert]

sometimes resolves instantly but module.code is still null

That should not happen, would be interested if you could reproduce it.

[KaelWD]

Sure: https://github.com/KaelWD/rollup-load-null

[lukastaegert]

Thanks so much, there was actually a bug in the logic. Fix at #4296. Now it should be reliable.