Fix hashicorp#106 composeAzureResourceID doesn't generate consistent …

…results

azurerm/resourceid.go

@@ -3,18 +3,22 @@ package azurerm
 import (
 	"fmt"
 	"net/url"
+	"sort"
 	"strings"
 )
 
 // ResourceID represents a parsed long-form Azure Resource Manager ID
 // with the Subscription ID, Resource Group and the Provider as top-
 // level fields, and other key-value pairs available via a map in the
-// Path field.
+// Path field. When a ResourceID instance is used to compose a resource
+// ID string, the PathOrder must specify the order of the items in Path
+// since map itself can only be iterated in random order.
 type ResourceID struct {
 	SubscriptionID string
 	ResourceGroup  string
 	Provider       string
 	Path           map[string]string
+	PathOrder      map[int]string
 }
 
 // parseAzureResourceID converts a long-form Azure Resource Manager ID
@@ -113,9 +117,21 @@ func composeAzureResourceID(idObj *ResourceID) (id string, err error) {
 			return "", fmt.Errorf("ResourceID.Path should have at least one item when ResourceID.Provider is specified")
 		}
 
+		if len(idObj.PathOrder) != len(idObj.Path) {
+			return "", fmt.Errorf("ResourceID.PathOrder must have the same number of elements as ResourceID.Path")
+		}
+
 		id += fmt.Sprintf("/providers/%s", idObj.Provider)
 
-		for k, v := range idObj.Path {
+		var keys []int
+		for k := range idObj.PathOrder {
+			keys = append(keys, k)
+		}
+		sort.Ints(keys)
+
+		for _, i := range keys {
+			k := idObj.PathOrder[i]
+			v := idObj.Path[k]
 			if k == "" || v == "" {
 				return "", fmt.Errorf("ResourceID.Path cannot contain empty strings")
 			}

azurerm/resourceid_test.go

@@ -160,6 +160,11 @@ func TestComposeAzureResourceID(t *testing.T) {
 					"k2": "v2",
 					"k3": "v3",
 				},
+				PathOrder: map[int]string{
+					0: "k1",
+					1: "k2",
+					2: "k3",
+				},
 			},
 			"/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/testGroup1/providers/foo.bar/k1/v1/k2/v2/k3/v3",
 			false,
@@ -192,6 +197,10 @@ func TestComposeAzureResourceID(t *testing.T) {
 					"k2": "v2",
 					"":   "v1",
 				},
+				PathOrder: map[int]string{
+					0: "k2",
+					1: "",
+				},
 			},
 			"",
 			true,
@@ -206,6 +215,29 @@ func TestComposeAzureResourceID(t *testing.T) {
 					"k1": "v1",
 					"k2": "",
 				},
+				PathOrder: map[int]string{
+					0: "k1",
+					1: "k2",
+				},
+			},
+			"",
+			true,
+		},
+		{
+			// Number of items in Path doesn't match PathOrder
+			&ResourceID{
+				SubscriptionID: "00000000-0000-0000-0000-000000000000",
+				ResourceGroup:  "testGroup1",
+				Provider:       "foo.bar",
+				Path: map[string]string{
+					"k1": "v1",
+					"k2": "",
+				},
+				PathOrder: map[int]string{
+					0: "k1",
+					1: "k2",
+					2: "k3",
+				},
 			},
 			"",
 			true,