Use public APIs for FunctionMap keyword validation

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

Author: ChrisRackauckas

lib/OrdinaryDiffEqFunctionMap/src/algorithms.jl

@@ -17,16 +17,15 @@ FunctionMap{scale_by_time}() where {scale_by_time} = FunctionMap{scale_by_time,
     trivial_limiter!
 )
 function FunctionMap(; scale_by_time = false, step_limiter = trivial_limiter!, kwargs...)
-    kwargs_nt = values(kwargs)
     old_kw = Symbol("step_limiter!")
-    if haskey(kwargs_nt, old_kw)
+    if haskey(kwargs, old_kw)
         if step_limiter === trivial_limiter!
-            step_limiter = get(kwargs_nt, old_kw, trivial_limiter!)
+            step_limiter = get(kwargs, old_kw, trivial_limiter!)
         end
     end
-    extra_kwargs = Base.structdiff(kwargs_nt, NamedTuple{(old_kw,)})
-    if !isempty(extra_kwargs)
-        throw(ArgumentError("Unsupported keyword argument(s): $(keys(extra_kwargs))"))
+    unsupported_kwargs = filter(!=(old_kw), keys(kwargs))
+    if !isempty(unsupported_kwargs)
+        throw(ArgumentError("Unsupported keyword argument(s): $(unsupported_kwargs)"))
     end
 
     return FunctionMap{scale_by_time, typeof(step_limiter)}(step_limiter)

lib/OrdinaryDiffEqFunctionMap/test/discrete_algorithm_test.jl

@@ -63,3 +63,17 @@ end
 
     @test sol3.u == [[0, 0], [1, 1], [2, 3], [3, 6], [4, 10], [5, 15]]
 end
+
+@testset "FunctionMap keyword validation" begin
+    current_limiter!(u, integrator, p, t) = nothing
+    legacy_limiter!(u, integrator, p, t) = nothing
+
+    @test FunctionMap(step_limiter = current_limiter!).step_limiter! === current_limiter!
+    @test FunctionMap(; step_limiter! = legacy_limiter!).step_limiter! === legacy_limiter!
+    @test_throws ArgumentError("Unsupported keyword argument(s): (:unsupported,)") FunctionMap(
+        unsupported = true
+    )
+    @test_throws ArgumentError(
+        "Unsupported keyword argument(s): (:unsupported, :also_unsupported)"
+    ) FunctionMap(unsupported = true, also_unsupported = true)
+end