From 87948b68fc742d5fbea3856c1f75ae2e99dd13aa Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Fri, 16 Jan 2015 09:32:15 -0800
Subject: [PATCH] helper/schema: use interface for equality check

/cc @svanharmelen
---
 helper/schema/equal.go         |  6 ++++++
 helper/schema/resource_data.go | 10 +++++-----
 helper/schema/set.go           | 10 ++++++++++
 3 files changed, 21 insertions(+), 5 deletions(-)
 create mode 100644 helper/schema/equal.go

diff --git a/helper/schema/equal.go b/helper/schema/equal.go
new file mode 100644
index 000000000..d5e20e038
--- /dev/null
+++ b/helper/schema/equal.go
@@ -0,0 +1,6 @@
+package schema
+
+// Equal is an interface that checks for deep equality between two objects.
+type Equal interface {
+	Equal(interface{}) bool
+}
diff --git a/helper/schema/resource_data.go b/helper/schema/resource_data.go
index 35107f3a4..924b9a877 100644
--- a/helper/schema/resource_data.go
+++ b/helper/schema/resource_data.go
@@ -106,11 +106,11 @@ func (d *ResourceData) getRaw(key string, level getSource) getResult {
 func (d *ResourceData) HasChange(key string) bool {
 	o, n := d.GetChange(key)
 
-	// There is a special case needed for *schema.Set's as they contain
-	// a function and reflect.DeepEqual will only say two functions are
-	// equal when they are both nil (which in this case they are not).
-	if reflect.TypeOf(o).String() == "*schema.Set" {
-		return !reflect.DeepEqual(o.(*Set).m, n.(*Set).m)
+	// If the type implements the Equal interface, then call that
+	// instead of just doing a reflect.DeepEqual. An example where this is
+	// needed is *Set
+	if eq, ok := o.(Equal); ok {
+		return !eq.Equal(n)
 	}
 
 	return !reflect.DeepEqual(o, n)
diff --git a/helper/schema/set.go b/helper/schema/set.go
index 78c68bdb7..965ad6f8b 100644
--- a/helper/schema/set.go
+++ b/helper/schema/set.go
@@ -2,6 +2,7 @@ package schema
 
 import (
 	"fmt"
+	"reflect"
 	"sort"
 	"sync"
 )
@@ -101,6 +102,15 @@ func (s *Set) Union(other *Set) *Set {
 	return result
 }
 
+func (s *Set) Equal(raw interface{}) bool {
+	other, ok := raw.(*Set)
+	if !ok {
+		return false
+	}
+
+	return reflect.DeepEqual(s.m, other.m)
+}
+
 func (s *Set) GoString() string {
 	return fmt.Sprintf("*Set(%#v)", s.m)
 }