trixi-framework · DanielDoehring · Nov 4, 2025 · Nov 4, 2025 · Nov 6, 2025 · Nov 6, 2025
diff --git a/NEWS.md b/NEWS.md
@@ -6,6 +6,14 @@ used in the Julia ecosystem. Notable changes will be documented in this file
 for human readability.
 
 
+## Changes when updating to v0.14 from v0.13.x
+
+#### Changed
+
+- A couple `struct`s have been made completely immutable, or only a couple fields thereof.
+Most notably, `save_solution.condition.save_initial_solution` where `save_solution isa SavesolutionCallback` can now longer be directly changed.
+Instead, the `@reset` macro from [Accessors.jl](https://github.com/JuliaObjects/Accessors.jl) is used in the elixirs instead.
+
 ## Changes when updating to v0.13 from v0.12.x
 
 #### Changed

diff --git a/examples/p4est_2d_dgsem/elixir_advection_restart.jl b/examples/p4est_2d_dgsem/elixir_advection_restart.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -26,7 +27,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 integrator = init(ode, CarpenterKennedy2N54(williamson_condition = false);
                   dt = dt, # solve needs some value here but it will be overwritten by the stepsize_callback

diff --git a/examples/p4est_2d_dgsem/elixir_advection_restart_amr.jl b/examples/p4est_2d_dgsem/elixir_advection_restart_amr.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -26,7 +27,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 # Add AMR callback
 amr_controller = ControllerThreeLevel(semi, IndicatorMax(semi, variable = first),

diff --git a/examples/p4est_3d_dgsem/elixir_advection_restart.jl b/examples/p4est_3d_dgsem/elixir_advection_restart.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -24,7 +25,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 integrator = init(ode, CarpenterKennedy2N54(williamson_condition = false);
                   dt = dt, # solve needs some value here but it will be overwritten by the stepsize_callback

diff --git a/examples/structured_2d_dgsem/elixir_advection_restart.jl b/examples/structured_2d_dgsem/elixir_advection_restart.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -25,7 +26,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 integrator = init(ode, CarpenterKennedy2N54(williamson_condition = false);
                   dt = dt, # solve needs some value here but it will be overwritten by the stepsize_callback

diff --git a/examples/structured_3d_dgsem/elixir_advection_restart.jl b/examples/structured_3d_dgsem/elixir_advection_restart.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -24,7 +25,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 integrator = init(ode, CarpenterKennedy2N54(williamson_condition = false);
                   dt = dt, # solve needs some value here but it will be overwritten by the stepsize_callback

diff --git a/examples/t8code_2d_dgsem/elixir_advection_restart.jl b/examples/t8code_2d_dgsem/elixir_advection_restart.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -26,7 +27,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 integrator = init(ode, CarpenterKennedy2N54(williamson_condition = false);
                   dt = dt, # solve needs some value here but it will be overwritten by the stepsize_callback

diff --git a/examples/t8code_2d_dgsem/elixir_advection_restart_amr.jl b/examples/t8code_2d_dgsem/elixir_advection_restart_amr.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -26,7 +27,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 # Add AMR callback
 amr_controller = ControllerThreeLevel(semi, IndicatorMax(semi, variable = first),

diff --git a/examples/t8code_3d_dgsem/elixir_advection_restart.jl b/examples/t8code_3d_dgsem/elixir_advection_restart.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -24,7 +25,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 integrator = init(ode, CarpenterKennedy2N54(williamson_condition = false);
                   dt = dt, # solve needs some value here but it will be overwritten by the stepsize_callback

diff --git a/examples/tree_2d_dgsem/elixir_advection_restart.jl b/examples/tree_2d_dgsem/elixir_advection_restart.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # Define time integration algorithm
@@ -25,7 +26,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 integrator = init(ode, alg;
                   dt = dt, # solve needs some value here but it will be overwritten by the stepsize_callback

diff --git a/examples/tree_2d_dgsem/elixir_advection_restart_amr.jl b/examples/tree_2d_dgsem/elixir_advection_restart_amr.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # Define time integration algorithm
@@ -24,7 +25,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 # Add AMR callback
 amr_controller = ControllerThreeLevel(semi, IndicatorMax(semi, variable = first),

diff --git a/examples/tree_3d_dgsem/elixir_advection_restart.jl b/examples/tree_3d_dgsem/elixir_advection_restart.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -22,7 +23,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 integrator = init(ode, CarpenterKennedy2N54(williamson_condition = false);
                   dt = dt, # solve needs some value here but it will be overwritten by the stepsize_callback

diff --git a/examples/unstructured_2d_dgsem/elixir_euler_restart.jl b/examples/unstructured_2d_dgsem/elixir_euler_restart.jl
@@ -1,5 +1,6 @@
 using OrdinaryDiffEqLowStorageRK
 using Trixi
+using Accessors: @reset
 
 ###############################################################################
 # create a restart file
@@ -24,7 +25,7 @@ dt = load_dt(restart_filename)
 ode = semidiscretize(semi, tspan, restart_filename)
 
 # Do not overwrite the initial snapshot written by elixir_advection_extended.jl.
-save_solution.condition.save_initial_solution = false
+@reset save_solution.condition.save_initial_solution = false
 
 integrator = init(ode, CarpenterKennedy2N54(williamson_condition = false);
                   dt = dt, # solve needs some value here but it will be overwritten by the stepsize_callback

diff --git a/src/callbacks_stage/entropy_bounded_limiter.jl b/src/callbacks_stage/entropy_bounded_limiter.jl
@@ -5,7 +5,7 @@
 @muladd begin
 #! format: noindent
 
-mutable struct EntropyBoundedLimiter{RealT <: Real}
+struct EntropyBoundedLimiter{RealT <: Real}
     exp_entropy_decrease_max::RealT # < 0
 end
 

diff --git a/src/callbacks_step/alive.jl b/src/callbacks_step/alive.jl
@@ -15,8 +15,8 @@ time steps. If `analysis_interval ≂̸ 0`, the output is omitted every
 """
 mutable struct AliveCallback
     start_time::Float64
-    alive_interval::Int
-    analysis_interval::Int
+    const alive_interval::Int
+    const analysis_interval::Int
 end
 
 function AliveCallback(; analysis_interval = 0,

diff --git a/src/callbacks_step/analysis.jl b/src/callbacks_step/analysis.jl
@@ -49,15 +49,15 @@ mutable struct AnalysisCallback{Analyzer, AnalysisIntegrals, InitialStateIntegra
     start_time_last_analysis::Float64
     ncalls_rhs_last_analysis::Int
     start_gc_time::Float64
-    interval::Int
-    save_analysis::Bool
-    output_directory::String
-    analysis_filename::String
-    analyzer::Analyzer
-    analysis_errors::Vector{Symbol}
-    analysis_integrals::AnalysisIntegrals
+    const interval::Int
+    const save_analysis::Bool
+    const output_directory::String
+    const analysis_filename::String
+    const analyzer::Analyzer
+    const analysis_errors::Vector{Symbol}
+    const analysis_integrals::AnalysisIntegrals
     initial_state_integrals::InitialStateIntegrals
-    cache::Cache
+    const cache::Cache
 end
 
 # TODO: Taal bikeshedding, implement a method with less information and the signature

diff --git a/src/callbacks_step/save_restart.jl b/src/callbacks_step/save_restart.jl
@@ -12,7 +12,7 @@
 
 Save the current numerical solution in a restart file every `interval` time steps.
 """
-mutable struct SaveRestartCallback
+struct SaveRestartCallback
     interval::Int
     save_final_restart::Bool
     output_directory::String

diff --git a/src/callbacks_step/save_solution.jl b/src/callbacks_step/save_solution.jl
@@ -42,7 +42,7 @@ function get_node_variable(::Val{symbol}, u, mesh, equations, dg, cache,
 end
 ```
 """
-mutable struct SaveSolutionCallback{IntervalType, SolutionVariablesType}
+struct SaveSolutionCallback{IntervalType, SolutionVariablesType}
     interval_or_dt::IntervalType
     save_initial_solution::Bool
     save_final_solution::Bool

diff --git a/src/callbacks_step/steady_state.jl b/src/callbacks_step/steady_state.jl
@@ -11,7 +11,7 @@
 Terminates the integration when the [`residual_steady_state(du, equations)`](@ref)
 falls below the threshold specified by `abstol, reltol`.
 """
-mutable struct SteadyStateCallback{RealT <: Real}
+struct SteadyStateCallback{RealT <: Real}
     abstol::RealT
     reltol::RealT
 end

diff --git a/src/callbacks_step/stepsize.jl b/src/callbacks_step/stepsize.jl
@@ -27,7 +27,7 @@ diffusive CFL number, or a function of time `t` returning a `Real` number.
 By default, the timestep will be adjusted at every step.
 For different values of `interval`, the timestep will be adjusted every `interval` steps.
 """
-mutable struct StepsizeCallback{CflAdvectiveType, CflDiffusiveType}
+struct StepsizeCallback{CflAdvectiveType, CflDiffusiveType}
     cfl_advective::CflAdvectiveType
     cfl_diffusive::CflDiffusiveType
     interval::Int

diff --git a/src/callbacks_step/time_series.jl b/src/callbacks_step/time_series.jl
@@ -27,12 +27,12 @@ Currently this callback is only implemented for [`TreeMesh`](@ref) and [`Unstruc
 """
 mutable struct TimeSeriesCallback{RealT <: Real, uEltype <: Real, SolutionVariables,
                                   VariableNames, Cache}
-    interval::Int
-    solution_variables::SolutionVariables
-    variable_names::VariableNames
-    output_directory::String
-    filename::String
-    point_coordinates::Array{RealT, 2}
+    const interval::Int
+    const solution_variables::SolutionVariables
+    const variable_names::VariableNames
+    const output_directory::String
+    const filename::String
+    const point_coordinates::Array{RealT, 2}
     # Point data is stored as a vector of vectors of the solution data type:
     # * the "outer" `Vector` contains one vector for each point at which a time_series is recorded
     # * the "inner" `Vector` contains the actual time series for a single point,
@@ -42,7 +42,7 @@ mutable struct TimeSeriesCallback{RealT <: Real, uEltype <: Real, SolutionVariab
     point_data::Vector{Vector{uEltype}}
     time::Vector{RealT}
     step::Vector{Int}
-    time_series_cache::Cache
+    const time_series_cache::Cache
 end
 
 function Base.show(io::IO, cb::DiscreteCallback{<:Any, <:TimeSeriesCallback})

diff --git a/src/callbacks_step/visualization.jl b/src/callbacks_step/visualization.jl
@@ -5,8 +5,8 @@
 @muladd begin
 #! format: noindent
 
-mutable struct VisualizationCallback{PlotDataCreator, SolutionVariables, VariableNames,
-                                     PlotCreator}
+struct VisualizationCallback{PlotDataCreator, SolutionVariables, VariableNames,
+                             PlotCreator}
     plot_data_creator::PlotDataCreator
     interval::Int
     solution_variables::SolutionVariables

diff --git a/src/equations/ideal_glm_mhd_multiion_2d.jl b/src/equations/ideal_glm_mhd_multiion_2d.jl
@@ -82,9 +82,9 @@ References:
     In case of more than one ion species, the multi-ion GLM-MHD equations should ALWAYS be used
     with [`source_terms_lorentz`](@ref).
 """
-mutable struct IdealGlmMhdMultiIonEquations2D{NVARS, NCOMP, RealT <: Real,
-                                              ElectronPressure, ElectronTemperature} <:
-               AbstractIdealGlmMhdMultiIonEquations{2, NVARS, NCOMP}
+struct IdealGlmMhdMultiIonEquations2D{NVARS, NCOMP, RealT <: Real,
+                                      ElectronPressure, ElectronTemperature} <:
+       AbstractIdealGlmMhdMultiIonEquations{2, NVARS, NCOMP}
     gammas::SVector{NCOMP, RealT} # Heat capacity ratios
     charge_to_mass::SVector{NCOMP, RealT} # Charge to mass ratios
     gas_constants::SVector{NCOMP, RealT} # Specific gas constants

diff --git a/src/equations/ideal_glm_mhd_multiion_3d.jl b/src/equations/ideal_glm_mhd_multiion_3d.jl
@@ -38,9 +38,9 @@ References:
     In case of more than one ion species, the multi-ion GLM-MHD equations should ALWAYS be used
     with [`source_terms_lorentz`](@ref).
 """
-mutable struct IdealGlmMhdMultiIonEquations3D{NVARS, NCOMP, RealT <: Real,
-                                              ElectronPressure} <:
-               AbstractIdealGlmMhdMultiIonEquations{3, NVARS, NCOMP}
+struct IdealGlmMhdMultiIonEquations3D{NVARS, NCOMP, RealT <: Real,
+                                      ElectronPressure} <:
+       AbstractIdealGlmMhdMultiIonEquations{3, NVARS, NCOMP}
     gammas::SVector{NCOMP, RealT} # Heat capacity ratios
     charge_to_mass::SVector{NCOMP, RealT} # Charge to mass ratios
     electron_pressure::ElectronPressure # Function to compute the electron pressure

diff --git a/src/meshes/dgmulti_meshes.jl b/src/meshes/dgmulti_meshes.jl
@@ -13,9 +13,9 @@ dispatchable type. This is intended to store geometric data and connectivities f
 mesh (Cartesian, affine, curved, structured/unstructured).
 """
 mutable struct DGMultiMesh{NDIMS, MeshType, MeshDataT <: MeshData{NDIMS}, BoundaryFaceT}
-    md::MeshDataT
+    const md::MeshDataT
 
-    boundary_faces::BoundaryFaceT
+    const boundary_faces::BoundaryFaceT
 
     current_filename :: String
     unsaved_changes  :: Bool

diff --git a/src/meshes/p4est_mesh.jl b/src/meshes/p4est_mesh.jl
@@ -24,17 +24,17 @@ mesh for a two-dimensional surface or shell in three-dimensional space.
 mutable struct P4estMesh{NDIMS, NDIMS_AMBIENT, RealT <: Real, IsParallel, P, Ghost,
                          NDIMSP2, NNODES} <:
                AbstractMesh{NDIMS}
-    p4est       :: P # Either PointerWrapper{p4est_t} or PointerWrapper{p8est_t}
-    is_parallel :: IsParallel
-    ghost       :: Ghost # Either PointerWrapper{p4est_ghost_t} or PointerWrapper{p8est_ghost_t}
+    const p4est::P # Either PointerWrapper{p4est_t} or PointerWrapper{p8est_t}
+    const is_parallel::IsParallel
+    ghost::Ghost # Either PointerWrapper{p4est_ghost_t} or PointerWrapper{p8est_ghost_t}
     # Coordinates at the nodes specified by the tensor product of `nodes` (NDIMS times).
     # This specifies the geometry interpolation for each tree.
-    tree_node_coordinates::Array{RealT, NDIMSP2} # [dimension, i, j, k, tree]
-    nodes::SVector{NNODES, RealT}
-    boundary_names::Array{Symbol, 2}      # [face direction, tree]
+    const tree_node_coordinates::Array{RealT, NDIMSP2} # [dimension, i, j, k, tree]
+    const nodes::SVector{NNODES, RealT}
+    boundary_names::Array{Symbol, 2} # [face direction, tree]
     current_filename::String
     unsaved_changes::Bool
-    p4est_partition_allow_for_coarsening::Bool
+    const p4est_partition_allow_for_coarsening::Bool
 
     function P4estMesh{NDIMS}(p4est, tree_node_coordinates, nodes, boundary_names,
                               current_filename, unsaved_changes,