Support slices in SetArg()

gomock/call.go

@@ -118,7 +118,8 @@ func (c *Call) Times(n int) *Call {
 }
 
 // SetArg declares an action that will set the nth argument's value,
-// indirected through a pointer.
+// indirected through a pointer. Or, in the case of a slice, SetArg
+// will copy value's elements into the nth argument.
 func (c *Call) SetArg(n int, value interface{}) *Call {
 	if c.setArgs == nil {
 		c.setArgs = make(map[int]reflect.Value)
@@ -142,8 +143,10 @@ func (c *Call) SetArg(n int, value interface{}) *Call {
 		}
 	case reflect.Interface:
 		// nothing to do
+	case reflect.Slice:
+		// nothing to do
 	default:
-		c.t.Fatalf("SetArg(%d, ...) referring to argument of non-pointer non-interface type %v [%s]",
+		c.t.Fatalf("SetArg(%d, ...) referring to argument of non-pointer non-interface non-slice type %v",
 			n, at, c.origin)
 	}
 	c.setArgs[n] = reflect.ValueOf(value)
@@ -243,7 +246,12 @@ func (c *Call) call(args []interface{}) (rets []interface{}, action func()) {
 		action = func() { c.doFunc.Call(doArgs) }
 	}
 	for n, v := range c.setArgs {
-		reflect.ValueOf(args[n]).Elem().Set(v)
+		switch reflect.TypeOf(args[n]).Kind() {
+		case reflect.Slice:
+			setSlice(args[n], v)
+		default:
+			reflect.ValueOf(args[n]).Elem().Set(v)
+		}
 	}
 
 	rets = c.rets
@@ -265,3 +273,10 @@ func InOrder(calls ...*Call) {
 		calls[i].After(calls[i-1])
 	}
 }
+
+func setSlice(arg interface{}, v reflect.Value) {
+	va := reflect.ValueOf(arg)
+	for i := 0; i < v.Len(); i++ {
+		va.Index(i).Set(v.Index(i))
+	}
+}

gomock/call_test.go

@@ -1,6 +1,9 @@
 package gomock
 
-import "testing"
+import (
+	"reflect"
+	"testing"
+)
 
 type mockTestReporter struct {
 	errorCalls int
@@ -45,3 +48,32 @@ func TestCall_After(t *testing.T) {
 		}
 	})
 }
+
+func TestCall_SetArg(t *testing.T) {
+	t.Run("SetArgSlice", func(t *testing.T) {
+		c := &Call{
+			methodType: reflect.TypeOf(func([]byte) {}),
+		}
+		c.SetArg(0, []byte{1, 2, 3})
+
+		in := []byte{4, 5, 6}
+		c.call([]interface{}{in})
+
+		if in[0] != 1 || in[1] != 2 || in[2] != 3 {
+			t.Error("Expected SetArg() to modify input slice argument")
+		}
+	})
+
+	t.Run("SetArgPointer", func(t *testing.T) {
+		c := &Call{
+			methodType: reflect.TypeOf(func(*int) {}),
+		}
+		c.SetArg(0, 42)
+
+		in := 43
+		c.call([]interface{}{&in})
+		if in != 42 {
+			t.Error("Expected SetArg() to modify value pointed to by argument")
+		}
+	})
+}