fix(add): Reduce the chance of breaking the user's formatting

src/cargo/util/toml_mut/manifest.rs

@@ -496,6 +496,11 @@ fn fix_feature_activations(
     for idx in remove_list.iter().rev() {
         feature_values.remove(*idx);
     }
+    if !remove_list.is_empty() {
+        // HACK: Instead of cleaning up the users formatting from having removed a feature, we just
+        // re-format the whole feature list
+        feature_values.fmt();
+    }
 
     if status == DependencyStatus::Required {
         for value in feature_values.iter_mut() {
@@ -516,8 +521,6 @@ fn fix_feature_activations(
             }
         }
     }
-
-    feature_values.fmt();
 }
 
 pub fn str_or_1_len_table(item: &toml_edit::Item) -> bool {

tests/testsuite/cargo_add/preserve_features_table/out/Cargo.toml

@@ -9,7 +9,12 @@ edition = "2021"
 your-face = { version = "99999.0.0" }
 
 [features]
-default = ["a", "b", "c"]
+default = [
-a = ["your-face/nose"]
+  "a",
+  "b",
+  "c",
+]
+a = ["your-face/nose",  # but not the mouth and nose
+]
 b = []
 c = []