Merge pull request #1081 from SciML/ChrisRackauckas-patch-2

`nothing` is a perfectly valid nonlinear solver algorithm

Author: ChrisRackauckas

src/initialization.jl

@@ -267,9 +267,6 @@ function get_initial_values(prob, valp, f, alg::OverrideInit,
         success = true
     else
         nlsolve_alg = something(nlsolve_alg, alg.nlsolve, Some(nothing))
-        if nlsolve_alg === nothing && state_values(initprob) !== nothing
-            throw(OverrideInitMissingAlgorithm())
-        end
         if alg.abstol !== nothing
             _abstol = alg.abstol
         elseif abstol !== nothing

test/downstream/initialization.jl

@@ -241,9 +241,11 @@ end
     @test SciMLBase.initialization_status(prob) == SciMLBase.FULLY_DETERMINED
     integ = init(prob; initializealg = NoInit())
 
-    @testset "Errors without `nlsolve_alg`" begin
-        @test_throws SciMLBase.OverrideInitMissingAlgorithm SciMLBase.get_initial_values(
-            prob, integ, fn, SciMLBase.OverrideInit(), Val(false))
+    @testset "Works without `nlsolve_alg`" begin
+        abstol = 1e-10
+        reltol = 1e-8
+        SciMLBase.get_initial_values(
+            prob, integ, fn, SciMLBase.OverrideInit(), Val(false); abstol, reltol)
     end
 
     abstol = 1e-10

test/initialization.jl

@@ -162,9 +162,11 @@ end
     @test SciMLBase.initialization_status(prob) == SciMLBase.FULLY_DETERMINED
     integ = init(prob; initializealg = NoInit())
 
-    @testset "Errors without `nlsolve_alg`" begin
-        @test_throws SciMLBase.OverrideInitMissingAlgorithm SciMLBase.get_initial_values(
-            prob, integ, fn, SciMLBase.OverrideInit(), Val(false))
+    @testset "Works without `nlsolve_alg`" begin
+        abstol = 1e-10
+        reltol = 1e-10
+        SciMLBase.get_initial_values(
+            prob, integ, fn, SciMLBase.OverrideInit(), Val(false); abstol, reltol)
     end
 
     abstol = 1e-10