fix for issue traefik#1634 -- for passing a closure to exported Go fu…

…nction

interp/interp_issue_1634_test.go

@@ -0,0 +1,58 @@
+package interp
+
+import (
+ "bytes"
+ "io"
+ "os"
+ "reflect"
+ "testing"
+)
+
+func TestExportClosureArg(t *testing.T) {
+ outExp := []byte("0\n1\n2\n")
+ // catch stdout
+ backupStdout := os.Stdout
+ defer func() {
+ os.Stdout = backupStdout
+ }()
+ r, w, _ := os.Pipe()
+ os.Stdout = w
+
+ i := New(Options{})
+ i.Use(Exports{
+ "tmp/tmp": map[string]reflect.Value{
+ "Func": reflect.ValueOf(func(s *[]func(), f func()) { *s = append(*s, f) }),
+ },
+ })
+ i.ImportUsed()
+
+ _, err := i.Eval(`
+func main() {
+ fs := []func(){}
+ 
+ for i := 0; i < 3; i++ {
+ i := i
+ tmp.Func(&fs, func() { println(i) })
+ }
+ for _, f := range fs {
+ f()
+ }
+}
+`)
+ if err != nil {
+ t.Error(err)
+ }
+
+ // read stdout
+ if err = w.Close(); err != nil {
+ t.Fatal(err)
+ }
+ outInterp, err := io.ReadAll(r)
+ if err != nil {
+ t.Fatal(err)
+ }
+ if !bytes.Equal(outInterp, outExp) {
+ t.Errorf("\nGot: %q,\n want: %q", string(outInterp), string(outExp))
+ }
+
+}

interp/run.go

@@ -987,7 +987,23 @@ func genFunctionWrapper(n *node) func(*frame) reflect.Value {
  }
  funcType := n.typ.TypeOf()
 
+ value := genValue(n)
+ isDefer := false
+ if n.anc != nil && n.anc.anc != nil && n.anc.anc.kind == deferStmt {
+ isDefer = true
+ }
+
  return func(f *frame) reflect.Value {
+ v := value(f)
+ if !isDefer && v.Kind() == reflect.Func {
+ // per #1634, if v is already a func, then don't re-wrap! critically, the original wrapping
+ // clones the frame, whereas the one here (below) does _not_ clone the frame, so it doesn't
+ // generate the proper closure capture effects!
+ // this path is the same as genValueAsFunctionWrapper which is the path taken above if
+ // the value has an associated node, which happens when you do f := func() ..
+ return v
+ }
+
  return reflect.MakeFunc(funcType, func(in []reflect.Value) []reflect.Value {
  // Allocate and init local frame. All values to be settable and addressable.
  fr := newFrame(f, len(def.types), f.runid())