handle keyword arguments

src/Chain.jl

@@ -10,19 +10,25 @@ insert_first_arg(symbol::Symbol, firstarg) = Expr(:call, symbol, firstarg)
 insert_first_arg(any, firstarg) = error("Can't insert an argument to $any. Needs to be a Symbol or a call expression")
 
 function insert_first_arg(e::Expr, firstarg)
+    head = e.head
+    args = e.args
 
     # f(a, b) --> f(firstarg, a, b)
-    if e.head == :call && length(e.args) > 1
-        Expr(e.head, e.args[1], firstarg, e.args[2:end]...)
+    if head == :call && length(args) > 1
+        if length(args) ≥ 2 && Meta.isexpr(args[2], :parameters)
+            Expr(head, args[1:2]..., firstarg, args[3:end]...)
+        else
+            Expr(head, args[1], firstarg, args[2:end]...)
+        end
 
     # @. somesymbol --> somesymbol.(firstarg)
-    elseif e.head == :macrocall && length(e.args) == 3 && e.args[1] == Symbol("@__dot__") &&
-            e.args[2] isa LineNumberNode && e.args[3] isa Symbol
-        Expr(:., e.args[3], Expr(:tuple, firstarg))
+    elseif head == :macrocall && length(args) == 3 && args[1] == Symbol("@__dot__") &&
+            args[2] isa LineNumberNode && args[3] isa Symbol
+        Expr(:., args[3], Expr(:tuple, firstarg))
 
     # @macro(a, b) --> @macro(firstarg, a, b)
-    elseif e.head == :macrocall && e.args[1] isa Symbol && e.args[2] isa LineNumberNode
-        Expr(e.head, e.args[1], e.args[2], firstarg, e.args[3:end]...)
+    elseif head == :macrocall && args[1] isa Symbol && args[2] isa LineNumberNode
+        Expr(head, args[1], args[2], firstarg, args[3:end]...)
 
     else
         error("Can't prepend first arg to expression $e that isn't a call.")
@@ -45,7 +51,7 @@ function rewrite(expr, replacement)
         replacement = gensym()
         new_expr = Expr(Symbol("="), replacement, new_expr)
     end
-    
+
     (new_expr, replacement)
 end
 

test/runtests.jl

@@ -133,7 +133,7 @@ macro broadcastminus(exp1, exp2)
 end
 
 @testset "splicing into macro calls" begin
-    
+
     x = 1
     y = @chain x begin
         @sin
@@ -208,4 +208,16 @@ end
             sum(_)
         end
     end)
-end
+end
+
+@testset "handling keyword argments" begin
+    f(a; kwarg) = (a, kwarg)
+    @test (:a, :kwarg) == @chain begin
+        :a
+        f(kwarg = :kwarg)
+    end
+    @test (:a, :kwarg) == @chain begin
+        :a
+        f(; kwarg = :kwarg)
+    end
+end