Merge pull request #1023 from SciML/myb/fix

Fix `connect` with varargs

Author: YingboMa

src/systems/abstractsystem.jl

@@ -715,7 +715,7 @@ end
 
 promote_connect_rule(::Type{T}, ::Type{S}) where {T, S} = Union{}
 promote_connect_rule(::Type{T}, ::Type{T}) where {T} = T
-promote_connect_type(t1::Type, t2::Type, ts::Type...) = promote_connect_rule(promote_connect_rule(t1, t2), ts...)
+promote_connect_type(t1::Type, t2::Type, ts::Type...) = promote_connect_type(promote_connect_rule(t1, t2), ts...)
 @inline function promote_connect_type(::Type{T}, ::Type{S}) where {T,S}
     promote_connect_result(
         T,

test/connectors.jl

@@ -13,9 +13,19 @@ end
     ODESystem(Equation[], t, [x], [p], defaults=Dict(x=>1.0, p=>1.0))
 end
 
-ModelingToolkit.connect(::Type{<:Foo}, sys1, sys2) = [sys1.x ~ sys2.x]
+function ModelingToolkit.connect(::Type{<:Foo}, ss...)
+    n = length(ss)-1
+    eqs = Vector{Equation}(undef, n)
+    for i in 1:n
+        eqs[i] = ss[i].x ~ ss[i+1].x
+    end
+    eqs
+end
+
 @named f1 = Foo()
 @named f2 = Foo()
+@named f3 = Foo()
+@named f4 = Foo()
 @named g = Goo()
 
 @test isequal(connect(f1, f2), [f1.x ~ f2.x])
@@ -24,6 +34,9 @@ ModelingToolkit.connect(::Type{<:Foo}, sys1, sys2) = [sys1.x ~ sys2.x]
 # Note that since there're overloadings, these tests are not re-runable.
 ModelingToolkit.promote_connect_rule(::Type{<:Foo}, ::Type{<:Goo}) = Foo
 @test isequal(connect(f1, g), [f1.x ~ g.x])
+@test isequal(connect(f1, f2, g), [f1.x ~ f2.x; f2.x ~ g.x])
+@test isequal(connect(f1, f2, g, f3), [f1.x ~ f2.x; f2.x ~ g.x; g.x ~ f3.x])
+@test isequal(connect(f1, f2, g, f3, f4), [f1.x ~ f2.x; f2.x ~ g.x; g.x ~ f3.x; f3.x ~ f4.x])
 ModelingToolkit.promote_connect_rule(::Type{<:Goo}, ::Type{<:Foo}) = Foo
 @test isequal(connect(f1, g), [f1.x ~ g.x])
 # test conflict