chore: improve printing of uninitialized variables

Author: DhairyaLGandhi

src/problems/initializationproblem.jl

@@ -84,7 +84,7 @@ All other keyword arguments are forwarded to the wrapped nonlinear problem const
     # TODO: throw on uninitialized arrays
     filter!(x -> !(x isa Symbolics.Arr), uninit)
     if time_dependent_init && !isempty(uninit)
-        allow_incomplete || throw(IncompleteInitializationError(uninit))
+        allow_incomplete || throw(IncompleteInitializationError(uninit, sys))
         # for incomplete initialization, we will add the missing variables as parameters.
         # they will be updated by `update_initializeprob!` and `initializeprobmap` will
         # use them to construct the new `u0`.
@@ -146,9 +146,10 @@ const INCOMPLETE_INITIALIZATION_MESSAGE = """
 
 struct IncompleteInitializationError <: Exception
     uninit::Any
+    sys::Any
 end
 
 function Base.showerror(io::IO, e::IncompleteInitializationError)
     println(io, INCOMPLETE_INITIALIZATION_MESSAGE)
-    println(io, e.uninit)
+    println(io, underscore_to_D(e.uninit, e.sys))
 end

src/utils.jl

@@ -1079,3 +1079,23 @@ function Base.showerror(io::IO, ::NotPossibleError)
     This should not be possible. Please open an issue in ModelingToolkit.jl with an MWE.
     """)
 end
+
+"""
+    $(TYPEDSIGNATURES)
+
+Given a vector of variables in the system, return the corresponding `Differential` form of variable if possible.
+Else returns the variable as-is.
+"""
+function underscore_to_D(v::AbstractVector, sys)
+    maps = get_schedule(sys).dummy_sub
+    inv_maps = Dict{valtype(maps), Vector{Base.keytype(maps)}}()
+
+    for (k, v) in maps
+        push!(get!(() -> valtype(inv_maps)[], inv_maps, v), k)
+    end
+    map(Base.Fix2(underscore_to_D, inv_maps), v)
+end
+
+function underscore_to_D(v, inv_map)
+    only(get(inv_map, v, [v]))
+end