From c1dbc71f8b41b62ebf160e40a774edb892080cf8 Mon Sep 17 00:00:00 2001
From: Leon Mika <lmika314@gmail.com>
Date: Sun, 29 Jul 2018 19:46:04 +1000
Subject: [PATCH] Added pointer dereferencing for field extraction

---
 eval_test.go | 33 +++++++++++++++++++++++++++++++++
 utils.go     |  5 +++++
 2 files changed, 38 insertions(+)

diff --git a/eval_test.go b/eval_test.go
index 00684e6cc..68c67f6fc 100644
--- a/eval_test.go
+++ b/eval_test.go
@@ -129,6 +129,11 @@ var evalTests = []evalTest{
 		struct{ Foo struct{ Bar bool } }{Foo: struct{ Bar bool }{Bar: true}},
 		true,
 	},
+	{
+		`Foo.Bar`,
+		&struct{ Foo *struct{ Bar bool } }{Foo: &struct{ Bar bool }{Bar: true}},
+		true,
+	},
 	{
 		"foo[2]",
 		map[string]interface{}{"foo": []rune{'a', 'b', 'c'}},
@@ -162,6 +167,29 @@ var evalTests = []evalTest{
 		}{1, 1},
 		true,
 	},
+	{
+		`[true][A]`,
+		&struct{ A int }{0},
+		true,
+	},
+	{
+		`A-1`,
+		&struct{ A int }{1},
+		float64(0),
+	},
+	{
+		`A == 0`,
+		&struct{ A uint8 }{0},
+		true,
+	},
+	{
+		`A == B`,
+		&struct {
+			A uint8
+			B float64
+		}{1, 1},
+		true,
+	},
 	{
 		`5 in 0..9`,
 		nil,
@@ -187,6 +215,11 @@ var evalTests = []evalTest{
 		map[string]interface{}{"foo": map[string]interface{}{"bar": map[string]interface{}{"baz": true}}},
 		true,
 	},
+	{
+		"foo.Bar['baz']",
+		map[string]interface{}{"foo": &struct{ Bar map[string]interface{}}{Bar: map[string]interface{}{"baz": true}}},
+		true,
+	},
 	{
 		`60 & 13`,
 		nil,
diff --git a/utils.go b/utils.go
index 2ae27bce3..64966bb5e 100644
--- a/utils.go
+++ b/utils.go
@@ -90,6 +90,11 @@ func extract(from interface{}, it interface{}) (interface{}, error) {
 			if value.IsValid() && value.CanInterface() {
 				return value.Interface(), nil
 			}
+		case reflect.Ptr:
+			derefValue := reflect.ValueOf(from).Elem()
+			if derefValue.IsValid() && derefValue.CanInterface() {
+				return extract(derefValue.Interface(), it)
+			}
 		}
 	}
 	return nil, fmt.Errorf("can't get %q from %T", it, from)