A way to make dependency requirements a bit more visible

[smoogipoo]

Some drawables require so many dependencies that it can be difficult to track what environment the object needs. One such example is https://github.com/ppy/osu/blob/master/osu.Game/Overlays/Chat/DrawableChatUsername.cs

C# still lacks the ability to merge XMLDocs (dotnet/roslyn#60730), so we can't simply specify the required dependencies in our generated partial classes. It seems to be random as to which definition it uses.

This post serves as a place to track and discuss, and includes my investigations into alternatives.

1. Factory methods

A .Factory() method on drawable objects with a single method containing the dependencies:

Try it out: https://github.com/smoogipoo/osu-framework/tree/sgen-di-create-method

2. Constructor cloning

Every constructor of the drawable object is cloned, and parameters are added for the dependencies:

Try it out: https://github.com/smoogipoo/osu-framework/tree/sgen-di-ctor-params

Unfortunately, this seems to behave badly with Go to Declaration or Usages. There's a slim chance this is happening because one of the types is unresolved:

3. Constructor cloning + dependency list

Constructors are weird because optional params must be placed at the end of them.

The order in (2) above is { origRequired, depsRequired, origOptional, depsOptional }, but this may not always be intuitive when there are both optional dependencies and optional arguments, which isn't illustrated by the example.

A dependency list is a single object that coalesces all of these parameters, and itself can be made optional and placed at the very end of the constructor. E.g.:

Try it out: https://github.com/smoogipoo/osu-framework/tree/sgen-di-ctor-dependencylist

This also suffers from intellisense woes as in (2).

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Note: The above examples may/will not compile. They're concepts.