Replace getSubgraphs() with a getSubgraphsIterator()

[guyca]

getSubgraphsIterator() will allow us to iterate lazily over subgraphs instead of prematurely instantiating all subgraphs.

[andre-krueger]

Will this also allow postponing the creation of a dependency which should be determined at the parent graph side?

As an example: A monorepo with a logger, which is used in multiple libraries and client and these clients need different implementations of that logger.
Basically the providing of a concrete implementation of that logger should happen in this example at the client's graph.

Currently I'm using an abstract graph for this, but then this abstract graph needs to be extended at the library side and there the correct implementation for a client via Obsidian.obtain is chosen. The downside is that this library now has unneeded dependencies which are only needed at the client side.

Beside the abstract graph, the only other solution I know of is using field injection.

I also tried providing a stub definition in the library graph and then overriding this on the client graph, but it seems that the library graph's definition always has precedence.

[guyca]

If I understood your use case correctly, abstract graphs seem like the right approach. But I'm not sure I understand why you need to use Obsidian.obtain to get the correct logger implementation. Using an abstract graph, you should define the correct logger implementation in the parent graph.

Also, thought I'd mention a few more things that might be related

1. The graphs form a DAG – a Directed Acyclic Graph – in which two-way relationships between graphs are not allowed.
2. Dependencies are created on demand when the provider is invoked.
3. If you want to delay the actual require of dependencies you should use inline requires. Something like this:

- import Foo from './foo';

@provides()
foo() {
+  const Foo = require('./foo');
  return new Foo();
}

4. In the future, I'll update the Babel and SWC plugins to automatically inline providers making all providers lazy by default (this will be configurable)

[guyca]

@andre-krueger This feels like a topic for a conversation, if you like you can reach out to me on Discord