feat: allow specifying problem_type using system metadata

Author: AayushSabharwal

src/problems/nonlinearproblem.jl

@@ -67,7 +67,8 @@ end
         check_length, check_compatibility, expression, kwargs...)
 
     kwargs = process_kwargs(sys; kwargs...)
-    args = (; f, u0, p, ptype = StandardNonlinearProblem())
+    ptype = getmetadata(sys, ProblemTypeCtx, StandardNonlinearProblem())
+    args = (; f, u0, p, ptype)
 
     return maybe_codegen_scimlproblem(expression, NonlinearProblem{iip}, args; kwargs...)
 end

src/problems/odeproblem.jl

@@ -77,7 +77,8 @@ end
     kwargs = process_kwargs(
         sys; expression, callback, eval_expression, eval_module, kwargs...)
 
-    args = (; f, u0, tspan, p, ptype = StandardODEProblem())
+    ptype = getmetadata(sys, ProblemTypeCtx, StandardODEProblem())
+    args = (; f, u0, tspan, p, ptype)
     maybe_codegen_scimlproblem(expression, ODEProblem{iip}, args; kwargs...)
 end
 

src/systems/system.jl

@@ -807,6 +807,16 @@ function SymbolicUtils.setmetadata(sys::AbstractSystem, k::DataType, v)
     @set sys.metadata = meta
 end
 
+"""
+    $(TYPEDSIGNATURES)
+
+Metadata key for systems containing the `problem_type` to be passed to the problem
+constructor, where applicable. For example, if `getmetadata(sys, ProblemTypeCtx, nothing)`
+is `CustomType()` then `ODEProblem(sys, ...).problem_type` will be `CustomType()` instead
+of `StandardODEProblem`.
+"""
+struct ProblemTypeCtx end
+
 """
     $(TYPEDSIGNATURES)
 """