add failing test for set elements with custom diff

Adding a DiffSuppressFunc for set elements can cause them to be missed
in the set diff entirely.

builtin/providers/test/provider.go

@@ -30,6 +30,7 @@ func Provider() terraform.ResourceProvider {
 			"test_resource_deprecated":       testResourceDeprecated(),
 			"test_resource_defaults":         testResourceDefaults(),
 			"test_resource_list":             testResourceList(),
+			"test_resource_list_set":         testResourceListSet(),
 			"test_resource_map":              testResourceMap(),
 			"test_resource_computed_set":     testResourceComputedSet(),
 		},

builtin/providers/test/resource_list_set.go

@@ -0,0 +1,73 @@
+package test
+
+import (
+	"fmt"
+	"math/rand"
+
+	"github.com/hashicorp/terraform/helper/schema"
+)
+
+func testResourceListSet() *schema.Resource {
+	return &schema.Resource{
+		Create: testResourceListSetCreate,
+		Read:   testResourceListSetRead,
+		Delete: testResourceListSetDelete,
+		Update: testResourceListSetUpdate,
+
+		Importer: &schema.ResourceImporter{
+			State: schema.ImportStatePassthrough,
+		},
+
+		Schema: map[string]*schema.Schema{
+			"list": {
+				Type:     schema.TypeList,
+				Optional: true,
+				MaxItems: 1,
+				Elem: &schema.Resource{
+					Schema: map[string]*schema.Schema{
+						"set": {
+							Type:     schema.TypeSet,
+							Optional: true,
+							Elem: &schema.Resource{
+								Schema: map[string]*schema.Schema{
+									"elem": {
+										Type:     schema.TypeString,
+										Optional: true,
+										DiffSuppressFunc: func(_, o, n string, _ *schema.ResourceData) bool {
+											return o == n
+										},
+									},
+								},
+							},
+							Set: func(v interface{}) int {
+								raw := v.(map[string]interface{})
+								if el, ok := raw["elem"]; ok {
+									return schema.HashString(el)
+								}
+								return 42
+							},
+						},
+					},
+				},
+			},
+		},
+	}
+}
+
+func testResourceListSetCreate(d *schema.ResourceData, meta interface{}) error {
+	d.SetId(fmt.Sprintf("%x", rand.Int63()))
+	return testResourceListSetRead(d, meta)
+}
+
+func testResourceListSetUpdate(d *schema.ResourceData, meta interface{}) error {
+	return testResourceListSetRead(d, meta)
+}
+
+func testResourceListSetRead(d *schema.ResourceData, meta interface{}) error {
+	return nil
+}
+
+func testResourceListSetDelete(d *schema.ResourceData, meta interface{}) error {
+	d.SetId("")
+	return nil
+}

builtin/providers/test/resource_list_set_test.go

@@ -0,0 +1,55 @@
+package test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/hashicorp/terraform/helper/resource"
+)
+
+func TestResourceListSet_basic(t *testing.T) {
+	resource.UnitTest(t, resource.TestCase{
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckResourceDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: strings.TrimSpace(`
+resource "test_resource_list_set" "foo" {
+  list {
+    set {
+      elem = "A"
+    }
+    set {
+      elem = "B"
+    }
+  }
+}
+				`),
+				Check: resource.ComposeTestCheckFunc(
+					resource.TestCheckResourceAttr("test_resource_list_set.foo", "list.0.set.1255198513.elem", "B"),
+					resource.TestCheckResourceAttr("test_resource_list_set.foo", "list.0.set.3554254475.elem", "A"),
+					resource.TestCheckResourceAttr("test_resource_list_set.foo", "list.0.set.#", "2"),
+				),
+			},
+			resource.TestStep{
+				Config: strings.TrimSpace(`
+resource "test_resource_list_set" "foo" {
+  list {
+    set {
+      elem = "B"
+    }
+    set {
+      elem = "C"
+    }
+  }
+}
+				`),
+				Check: resource.ComposeTestCheckFunc(
+					resource.TestCheckResourceAttr("test_resource_list_set.foo", "list.0.set.1255198513.elem", "B"),
+					resource.TestCheckResourceAttr("test_resource_list_set.foo", "list.0.set.1037565863.elem", "C"),
+					resource.TestCheckResourceAttr("test_resource_list_set.foo", "list.0.set.#", "2"),
+				),
+			},
+		},
+	})
+}