Fix: msgraph_resource fails to update resources when external changes are detected

CHANGELOG.md

@@ -14,6 +14,7 @@ DEPENDENCIES:
 - Updated `github.com/Azure/azure-sdk-for-go/sdk/azcore` from v1.16.0 to v1.19.1
 
 BUG FIXES:
+- Fixed an issue where `msgraph_resource` failed to update resources when external changes are detected, specifically when clearing array fields ([#58](https://github.com/microsoft/terraform-provider-msgraph/issues/58))
 - Fixed an issue where `msgraph_resource` failed to track state for `$ref` resources (relationships), causing drift detection failures ([#68](https://github.com/microsoft/terraform-provider-msgraph/issues/68))
 - Fixed an issue where `@odata.type` property was missing in PATCH requests for resources that require it (e.g. Named Locations) ([#59](https://github.com/microsoft/terraform-provider-msgraph/issues/59))
 

internal/services/msgraph_resource.go

@@ -342,7 +342,7 @@ func (r *MSGraphResource) Update(ctx context.Context, req resource.UpdateRequest
 		patchBody := utils.DiffObject(previousBody, requestBody, diffOption)
 
 		// If there's something to update, send PATCH
-		if !utils.IsEmptyObject(patchBody) {
+		if patchBody != nil {
 			_, err := r.client.Update(ctx, fmt.Sprintf("%s/%s", model.Url.ValueString(), model.Id.ValueString()), model.ApiVersion.ValueString(), patchBody, options)
 			if err != nil {
 				resp.Diagnostics.AddError("Failed to create resource", err.Error())

internal/services/msgraph_resource_test.go

@@ -278,6 +278,29 @@ func TestAcc_ResourceImport_InvalidIDFormat(t *testing.T) {
 	})
 }
 
+func TestAcc_ResourceApplicationRemovesPasswordCredentials(t *testing.T) {
+	data := acceptance.BuildTestData(t, "msgraph_resource", "test")
+
+	r := MSGraphTestResource{}
+
+	data.ResourceTest(t, r, []resource.TestStep{
+		{
+			Config: r.applicationWithPasswordCredentials(true),
+			Check: resource.ComposeTestCheckFunc(
+				check.That(data.ResourceName).Exists(r),
+				check.That(data.ResourceName).Key("id").IsUUID(),
+			),
+		},
+		{
+			Config: r.applicationWithPasswordCredentials(false),
+			Check: resource.ComposeTestCheckFunc(
+				check.That(data.ResourceName).Exists(r),
+				check.That(data.ResourceName).Key("id").IsUUID(),
+			),
+		},
+	})
+}
+
 func (r MSGraphTestResource) Exists(ctx context.Context, client *clients.Client, state *terraform.InstanceState) (*bool, error) {
 	apiVersion := state.Attributes["api_version"]
 	url := state.Attributes["url"]
@@ -601,3 +624,26 @@ resource "msgraph_resource" "test" {
 }
 `, displayName)
 }
+
+func (r MSGraphTestResource) applicationWithPasswordCredentials(enabled bool) string {
+	passwordCredential := ""
+	if enabled {
+		passwordCredential = `
+	  {
+		displayName = "first credential"
+	  }`
+	}
+
+	return fmt.Sprintf(`
+resource "msgraph_resource" "test" {
+  url = "applications"
+
+  body = {
+    displayName = "My Application"
+    passwordCredentials = [
+      %s
+    ]
+  }
+}
+`, passwordCredential)
+}

internal/utils/json.go

@@ -221,7 +221,7 @@ func DiffObject(old interface{}, new interface{}, option UpdateJsonOption) inter
 			// include keys present in new
 			for key, newVal := range newMap {
 				if oldVal, ok := oldValue[key]; ok {
-					if d := DiffObject(oldVal, newVal, option); !IsEmptyObject(d) {
+					if d := DiffObject(oldVal, newVal, option); d != nil {
 						res[key] = d
 					}
 				} else {
@@ -269,17 +269,3 @@ func DiffObject(old interface{}, new interface{}, option UpdateJsonOption) inter
 	// primitives or differing types -> return new
 	return new
 }
-
-// IsEmptyObject returns true if the input should be considered an empty patch
-func IsEmptyObject(v interface{}) bool {
-	if v == nil {
-		return true
-	}
-	switch t := v.(type) {
-	case map[string]interface{}:
-		return len(t) == 0
-	case []interface{}:
-		return len(t) == 0
-	}
-	return false
-}

internal/utils/json_test.go

@@ -295,6 +295,20 @@ func TestDiffObject(t *testing.T) {
 				"name": "changed",
 			},
 		},
+		{
+			name: "array changed to empty -> empty array returned (issue #58)",
+			old:  []interface{}{1, 2, 3},
+			newV: []interface{}{},
+			opt:  UpdateJsonOption{},
+			want: []interface{}{},
+		},
+		{
+			name: "nested array changed to empty -> parent map with empty array returned (issue #58)",
+			old:  map[string]interface{}{"a": []interface{}{1}},
+			newV: map[string]interface{}{"a": []interface{}{}},
+			opt:  UpdateJsonOption{},
+			want: map[string]interface{}{"a": []interface{}{}},
+		},
 	}
 	for _, tc := range testcases {
 		t.Run(tc.name, func(t *testing.T) {
@@ -305,24 +319,3 @@ func TestDiffObject(t *testing.T) {
 		})
 	}
 }
-
-func TestIsEmptyObject(t *testing.T) {
-	testcases := []struct {
-		name string
-		v    interface{}
-		want bool
-	}{
-		{name: "nil", v: nil, want: true},
-		{name: "empty map", v: map[string]interface{}{}, want: true},
-		{name: "empty slice", v: []interface{}{}, want: true},
-		{name: "scalar", v: "x", want: false},
-	}
-	for _, tc := range testcases {
-		t.Run(tc.name, func(t *testing.T) {
-			got := IsEmptyObject(tc.v)
-			if got != tc.want {
-				t.Fatalf("IsEmptyObject() = %v, want %v (input=%#v)", got, tc.want, tc.v)
-			}
-		})
-	}
-}