Make error norm calculation optional

src/callbacks_step/analysis.jl

@@ -377,8 +377,15 @@ function (analysis_callback::AnalysisCallback)(io, du, u, u_ode, t, semi)
         println()
     end
 
-    # Calculate L2/Linf errors, which are also returned
-    l2_error, linf_error = calc_error_norms(u_ode, t, analyzer, semi, cache_analysis)
+    if :l2_error in analysis_errors || :linf_error in analysis_errors
+        # Calculate L2/Linf errors, which are also returned
+        l2_error, linf_error = calc_error_norms(u_ode, t, analyzer, semi,
+                                                cache_analysis)
+    else
+        # Names `l2_error`, `linf_error` need to be defined
+        l2_error = nothing
+        linf_error = nothing
+    end
 
     if mpi_isroot()
         # L2 error

test/test_tree_1d_advection.jl

@@ -54,6 +54,20 @@ end
     end
 end
 
+@trixi_testset "elixir_advection_basic.jl (No errors)" begin
+    @test_trixi_include(joinpath(EXAMPLES_DIR, "elixir_advection_basic.jl"),
+                        analysis_callback=AnalysisCallback(semi, interval = 42,
+                                                           analysis_errors = Symbol[]))
+    # Ensure that we do not have excessive memory allocations
+    # (e.g., from type instabilities)
+    let
+        t = sol.t[end]
+        u_ode = sol.u[end]
+        du_ode = similar(u_ode)
+        @test (@allocated Trixi.rhs!(du_ode, u_ode, semi, t)) < 1000
+    end
+end
+
 @trixi_testset "elixir_advection_finite_volume.jl" begin
     @test_trixi_include(joinpath(EXAMPLES_DIR, "elixir_advection_finite_volume.jl"),
                         l2=[0.011662300515980219],