rule: set update flag on Rule.AddArg (bazelbuild#1702)

Otherwise the shortcut logic in Sync() will prevent the change to be
reflected in the syntax tree if no other action sets the updated flag.

rule/rule.go

@@ -997,6 +997,7 @@ func (r *Rule) Args() []bzl.Expr {
 // AddArg adds a positional argument to the rule.
 func (r *Rule) AddArg(value bzl.Expr) {
  r.args = append(r.args, value)
+ r.updated = true
 }
 
 // Insert marks this statement for insertion at the end of the file. Multiple

rule/rule_test.go

@@ -638,3 +638,31 @@ a_rule(
  t.Errorf("got:%s\nwant:%s", got, want)
  }
 }
+
+func TestSimpleArgument(t *testing.T) {
+ f := EmptyFile("foo", "bar")
+
+ r := NewRule("export_files", "")
+ r.AddArg(&bzl.CallExpr{
+ X: &bzl.Ident{Name: "glob"},
+ List: []bzl.Expr{
+ &bzl.ListExpr{
+ List: []bzl.Expr{
+ &bzl.StringExpr{Value: "**"},
+ },
+ },
+ },
+ })
+
+ r.Insert(f)
+ f.Sync()
+
+ got := strings.TrimSpace(string(bzl.FormatWithoutRewriting(f.File)))
+ want := strings.TrimSpace(`
+export_files(glob(["**"]))
+`)
+
+ if got != want {
+ t.Errorf("got:%s\nwant:%s", got, want)
+ }
+}