fix errors.NewAggregate nil pointer panic

Change-Id: I82b376898f9170d237a3bd1a1ac898cc6c636d12

pkg/util/errors/errors.go

@@ -31,11 +31,23 @@ type Aggregate interface {
 // NewAggregate converts a slice of errors into an Aggregate interface, which
 // is itself an implementation of the error interface.  If the slice is empty,
 // this returns nil.
+// It will check if any of the element of input error list is nil, to avoid
+// nil pointer panic when call Error().
 func NewAggregate(errlist []error) Aggregate {
 	if len(errlist) == 0 {
 		return nil
 	}
-	return aggregate(errlist)
+	// In case of input error list contains nil
+	var errs []error
+	for _, e := range errlist {
+		if e != nil {
+			errs = append(errs, e)
+		}
+	}
+	if len(errs) == 0 {
+		return nil
+	}
+	return aggregate(errs)
 }
 
 // This helper implements the error and Errors interfaces.  Keeping it private

pkg/util/errors/errors_test.go

@@ -50,6 +50,46 @@ func TestEmptyAggregate(t *testing.T) {
 	}
 }
 
+func TestAggregateWithNil(t *testing.T) {
+	var slice []error
+	slice = []error{nil}
+	var agg Aggregate
+	var err error
+
+	agg = NewAggregate(slice)
+	if agg != nil {
+		t.Errorf("expected nil, got %#v", agg)
+	}
+	err = NewAggregate(slice)
+	if err != nil {
+		t.Errorf("expected nil, got %#v", err)
+	}
+
+	// Append a non-nil error
+	slice = append(slice, fmt.Errorf("err"))
+	agg = NewAggregate(slice)
+	if agg == nil {
+		t.Errorf("expected non-nil")
+	}
+	if s := agg.Error(); s != "err" {
+		t.Errorf("expected 'err', got %q", s)
+	}
+	if s := agg.Errors(); len(s) != 1 {
+		t.Errorf("expected one-element slice, got %#v", s)
+	}
+	if s := agg.Errors()[0].Error(); s != "err" {
+		t.Errorf("expected 'err', got %q", s)
+	}
+
+	err = agg.(error)
+	if err == nil {
+		t.Errorf("expected non-nil")
+	}
+	if s := err.Error(); s != "err" {
+		t.Errorf("expected 'err', got %q", s)
+	}
+}
+
 func TestSingularAggregate(t *testing.T) {
 	var slice []error = []error{fmt.Errorf("err")}
 	var agg Aggregate