Personally, I containerize the weird build tools I can't fully trust (vendor toolchains etc) and have wrapper scripts (written in bash) in PATH. The IDE is none the wiser that those are containerized.
It's possible to have multiple packages in a permanent custom profile, if that's what you mean (that's kinda the manifest stuff at the end of the article). Those can be started all in the same container. For example, yes, you can have a profile which contains java-eclipse-jdt-core, gcc-toolchain and gfortran-toolchain for your specific project. This does not change your specific project's package.
If you are asking whether java-eclipse-jdt-core, gcc-toolchain and gfortran-toolchain would be referred to in your guix.scm, I wouldn't do that. But in your profile? yes.
>Would one need to install the IDE as a dependency of a project?
Why that? The IDE, like a text editor, is a developer tool and doesn't end up with the project artifacts that you are building. So it's not any kind of dependency of the project.
For example when you build Java projects using Eclipse, your projects are actually built using gradle and then openjdk. So gradle is a native-input, openjdk is a build system input and Eclipse is NO dependency of your project's guix package.
Your developer profile, however, can contain multiple packages (in the container). That's not what's built when you build just the package using "guix build -f guix.scm", though (those builds are isolated).
Think of a profile as something like as set of packages and also environment variables that you can refer to as a whole (containerize etc) using a new fixed name.
Or think of companies where you have different hats on. Depending on the hat, you would have a profile--so the developer hat doesn't actually have the tools to delete production :)
Most other distributions have just one global profile, not even per user. In guix, you have a default profile ".guix-profile" per user, and you can make any number of extra ones (no sudo needed).
>when you have multiple projects with different dependencies open at the same time?
Hmm, I think I can see what you are getting at. I don't know whether there are IDE plugins that are guix-aware. Would be easy to do though (it would just use a custom build step as the only build step - "guix build -f guix.scm" . This automatically makes a container with your package, its build system and your package's dependencies in it and builds that (if dependency is not built yet, makes a container with that package and its dependencies in it and builds that, and so on, recursively). The IDE would then pick up the output of "guix build" which is the path to the result (somewhere in /gnu/store/...)).
The path names used inside and outside the container are the same, and the dependencies are kept around for a while, so the IDE will have a good time referring to those for headers etc when debugging or doing autocomplete.