move disjunction name to a kwarg

this specifies the name of the binary variable for the disjunction (if 
missing, a name is generated)

Author: hdavid16

examples/ex1.jl

@@ -9,4 +9,4 @@ m = Model()
 @constraint(m, con3, x<=9)
 @constraint(m, con4, 5<=x)
 
-s=@disjunction(m,:y,(con1,con2),con3,con4,reformulation=:BMR)
+@disjunction(m,(con1,con2),con3,con4,reformulation=:CHR,name=:y)

src/disjunction.jl

@@ -1,16 +1,10 @@
-function add_disjunction(m::Model,args...;reformulation=:BMR,M=missing,eps=1e-6)
+function add_disjunction(m::Model,disj...;reformulation=:BMR,M=missing,eps=1e-6,name=missing)
     @assert m isa Model "A valid JuMP Model must be provided."
     @assert reformulation in [:BMR, :CHR] "Invalid reformulation method passed to keyword argument `:reformulation`. Valid options are :BMR (Big-M Reformulation) and :CHR (Convex-Hull Reormulation)."
 
     #create binary indicator variables for each disjunction
-    if args[1] isa Symbol #name for disjunction can be the first argument
-        @assert isnothing(variable_by_name(m,string(args[1]))) "Name for disjunction binary cannot be the same as an existing variable."
-        disj_name = args[1]
-        disj = args[2:end]
-    else #if name is not passed, then generate it
-        disj_name = Symbol("disj",gensym())
-        disj = args
-    end
+    disj_name = ismissing(name) ? Symbol("disj",gensym()) : name
+    @assert isnothing(variable_by_name(m,string(disj_name))) "Name for disjunction binary cannot be the same as an existing variable."
     eval(:(@variable($m, $disj_name[i = 1:length($disj)], Bin)))
     #enforce exclussive OR
     eval(:(@constraint($m,sum($disj_name[i] for i = 1:length($disj)) == 1)))

src/macro.jl

@@ -12,17 +12,13 @@ macro disjunction(args...)
     M = !isempty(M) ? esc(M[1].args[2]) : :(missing)
     eps = filter(i -> i.args[1] == :eps, kw_args)
     eps = !isempty(eps) ? esc(eps[1].args[2]) : :(1e-6)
+    name = filter(i -> i.args[1] == :name, kw_args)
+    name = !isempty(name) ? esc(name[1].args[2]) : :(missing)
 
     #get args
     m = esc(pos_args[1])
-    disj_name = pos_args[2]
-    if disj_name isa QuoteNode
-        disj = [esc(a) for a in pos_args[3:end]]
-    elseif isa(disj_name, Symbol) || Meta.isexpr(disj_name, (:tuple,:vect))
-        disj_name = :(Symbol("disj",gensym()))
-        disj = [esc(a) for a in pos_args[2:end]]
-    end
+    disj = [esc(a) for a in pos_args[2:end]]
 
     #build disjunction
-    :(add_disjunction($m, $disj_name, $(disj...), reformulation = $reformulation, M = $M, eps = $eps))
+    :(add_disjunction($m, $(disj...), reformulation = $reformulation, M = $M, eps = $eps, name = $name))
 end