Symbolic defaults for sub-components and base system kwargs + set base sys kwargs as component's kwargs

[ven-k]

1. Kwargs of sub-components and base systems (in extend) can now have symbolic defaults. This allows scenarios like:

@mtkmodel A begin
    @parameters begin
            a1 = 1
    end
    @components begin
           bb = B(; b1 = a1)
    end
end

Earlier, this would be A(; a1 = nothing, B.b1 = a1), where b1 would have default value set as a1 arguement.
Now, it is A(; a1 = nothing, B.b1 = nothing) and internally, default value of b1 is set to parameter a1.

2. While extending components, the kwargs of base system are promoted as kwargs of the main sys.

@mtkmodel D begin
     @extend e1, e2 = ee = E(; ek)
end

Earlier D would have a kwarg ee__ek (as if ee was a subcomponent). Now D will have ek as the kwarg. This avoids having to access partial components of a model to set parameters.

The model-parsing tests are updated to cover both the above changes.

[ai-maintainer]

AI-Maintainer Review for PR - Symbolic defaults for sub-components and base system kwargs + set base sys kwargs as component's kwargs

Title and Description 👍

The Title and Description are clear and concise

The title and description of the pull request are clear and concise. They effectively communicate the purpose of the changes, which is to introduce symbolic defaults for sub-components and base system kwargs, and to set base sys kwargs as component's kwargs. The description provides examples and explains how the new functionality works.

Scope of Changes 👍

The changes are narrowly focused

The changes appear to be narrowly focused on addressing specific issues related to the handling of kwargs in sub-components and base systems. The author is not trying to resolve multiple issues simultaneously but rather introducing new functionality and improving the behavior of the code in a targeted manner.

Documentation and Comments 👍

All new functions and methods have appropriate docstrings

All newly added functions, classes, or methods have docstrings describing their behavior, arguments, and return values. There are no functions, classes, or methods in the provided diff that need docstrings.

Testing 👎

Testing details are missing

The description does not mention how the author tested the changes. It would be helpful for the author to include information about the testing approach and any specific test cases used to verify the changes.

Suggested Changes

• Please provide details on how the changes were tested. This could include the specific test cases used to verify the changes and any testing frameworks used.

Reviewed with AI Maintainer

[ven-k]

• Tests involving MSL, fail due to the second change (Both integration test and few units tests: linearize.jl and input_output_handling.jl)
• refactor: kwargs of base system are now kwargs of main component ModelingToolkitStandardLibrary.jl#209 updates it accordingly.

[ven-k]

The Ai4EComponentLib, StructuralIdentifiability integration test failures are unrelated to the changes introduced here.

MTK test failure and MSL integration test failure is fixed by SciML/ModelingToolkitStandardLibrary.jl#209. However that needs this to be merged and released.

This is ready for review @YingboMa @ChrisRackauckas.

[baggepinnen]

In your first example, could the default value for b1 be an expression (not just a parameter), like

B(; b1 = a1^2)

?

Thanks for this PR, I have been missing this feature :)

[ven-k]

Expressions without conditional part work. (I'm working on the latter in a follow up PR)

So B(; b1 = a1^2) gives:

julia> @named aa = A(; a1 = 1)
Model aa with 0 equations
States (0):
Parameters (2):
  a1 [defaults to 1]
  bb₊b1 [defaults to a1^2]

julia> getdefault(aa.bb.b1)
a1^2

Something like B(; b1 = true ? a1 : 1) doesn't work yet.

[ven-k]

Additional to above changes, a new @structural_parameters is added to @mtkmodel. This allows arguments that aren't either parameters or variables, aka boolean flags, functions etc...

@mtkmodel A begin
    @structural_parameters begin
         a = 1
         b
    end
    @parameters begin
        c = 0
    end
end

A's arg list will be: A(; name, a = 1, b, c = nothing).

@YingboMa I've updated the tests to include this and rebased on current master. So this PR is ready for review.

[ven-k]

• And note that any test involving MSL fail for now and will need refactor: kwargs of base system are now kwargs of main component ModelingToolkitStandardLibrary.jl#209 (which updates MSL with the changes introduced by this PR)

[ven-k]

The branch is rebased wrt to master.

And note that any test involving MSL fail for now and will need

*To test locally use url = "https://github.com/ven-k/ModelingToolkitStandardLibrary.jl", rev = "vkb/extend-kwargs"