WIP: fix(add): Ensure comments are preserved

Fixes rust-lang#10849

src/cargo/ops/cargo_add/dependency.rs

@@ -490,17 +490,17 @@ impl Dependency {
         } else if let Some(table) = item.as_table_like_mut() {
             match &self.source {
                 Some(Source::Registry(src)) => {
-                    table.insert("version", toml_edit::value(src.version.as_str()));
+                    overwrite_value(table, "version", src.version.as_str());
 
                     for key in ["path", "git", "branch", "tag", "rev", "workspace"] {
                         table.remove(key);
                     }
                 }
                 Some(Source::Path(src)) => {
                     let relpath = path_field(crate_root, &src.path);
-                    table.insert("path", toml_edit::value(relpath));
+                    overwrite_value(table, "path", relpath);
                     if let Some(r) = src.version.as_deref() {
-                        table.insert("version", toml_edit::value(r));
+                        overwrite_value(table, "version", r);
                     } else {
                         table.remove("version");
                     }
@@ -510,24 +510,24 @@ impl Dependency {
                     }
                 }
                 Some(Source::Git(src)) => {
-                    table.insert("git", toml_edit::value(src.git.as_str()));
+                    overwrite_value(table, "git", src.git.as_str());
                     if let Some(branch) = src.branch.as_deref() {
-                        table.insert("branch", toml_edit::value(branch));
+                        overwrite_value(table, "branch", branch);
                     } else {
                         table.remove("branch");
                     }
                     if let Some(tag) = src.tag.as_deref() {
-                        table.insert("tag", toml_edit::value(tag));
+                        overwrite_value(table, "tag", tag);
                     } else {
                         table.remove("tag");
                     }
                     if let Some(rev) = src.rev.as_deref() {
-                        table.insert("rev", toml_edit::value(rev));
+                        overwrite_value(table, "rev", rev);
                     } else {
                         table.remove("rev");
                     }
                     if let Some(r) = src.version.as_deref() {
-                        table.insert("version", toml_edit::value(r));
+                        overwrite_value(table, "version", r);
                     } else {
                         table.remove("version");
                     }
@@ -537,7 +537,7 @@ impl Dependency {
                     }
                 }
                 Some(Source::Workspace(_)) => {
-                    table.insert("workspace", toml_edit::value(true));
+                    overwrite_value(table, "workspace", true);
                     table.set_dotted(true);
                     key.fmt();
                     for key in [
@@ -559,7 +559,7 @@ impl Dependency {
             }
             if table.contains_key("version") {
                 if let Some(r) = self.registry.as_deref() {
-                    table.insert("registry", toml_edit::value(r));
+                    overwrite_value(table, "registry", r);
                 } else {
                     table.remove("registry");
                 }
@@ -568,11 +568,11 @@ impl Dependency {
             }
 
             if self.rename.is_some() {
-                table.insert("package", toml_edit::value(self.name.as_str()));
+                overwrite_value(table, "package", self.name.as_str());
             }
             match self.default_features {
                 Some(v) => {
-                    table.insert("default-features", toml_edit::value(v));
+                    overwrite_value(table, "default-features", v);
                 }
                 None => {
                     table.remove("default-features");
@@ -590,29 +590,46 @@ impl Dependency {
                     })
                     .unwrap_or_default();
                 features.extend(new_features.iter().map(|s| s.as_str()));
-                let features = toml_edit::value(features.into_iter().collect::<toml_edit::Value>());
+                let features = features.into_iter().collect::<toml_edit::Value>();
                 table.set_dotted(false);
-                table.insert("features", features);
+                overwrite_value(table, "features", features);
             } else {
                 table.remove("features");
             }
             match self.optional {
                 Some(v) => {
                     table.set_dotted(false);
-                    table.insert("optional", toml_edit::value(v));
+                    overwrite_value(table, "optional", v);
                 }
                 None => {
                     table.remove("optional");
                 }
             }
-
-            table.fmt();
         } else {
             unreachable!("Invalid dependency type: {}", item.type_name());
         }
     }
 }
 
+/// Overwrite a value while preserving the original formatting
+fn overwrite_value(
+    table: &mut dyn toml_edit::TableLike,
+    key: &str,
+    value: impl Into<toml_edit::Value>,
+) {
+    let mut value = value.into();
+
+    let existing = table.entry(key).or_insert(toml_edit::Item::None);
+    let existing_decor = existing
+        .as_value()
+        .map(|v| v.decor().clone())
+        .unwrap_or_default();
+
+    *value.decor_mut() = existing_decor;
+
+    *existing = toml_edit::Item::Value(value);
+}
+
 fn invalid_type(dep: &str, key: &str, actual: &str, expected: &str) -> anyhow::Error {
     anyhow::format_err!("Found {actual} for {key} when {expected} was expected for {dep}")
 }

tests/testsuite/cargo_add/mod.rs

@@ -77,6 +77,7 @@ mod overwrite_optional_with_no_optional;
 mod overwrite_path_noop;
 mod overwrite_path_with_version;
 mod overwrite_preserves_inline_table;
+mod overwrite_preserves_std_table;
 mod overwrite_rename_with_no_rename;
 mod overwrite_rename_with_rename;
 mod overwrite_rename_with_rename_noop;

tests/testsuite/cargo_add/overwrite_preserves_std_table/in/Cargo.toml

@@ -0,0 +1,9 @@
+[workspace]
+
+[package]
+name = "cargo-list-test-fixture"
+version = "0.0.0"
+
+[dependencies.your-face]
+version="99999.0.0"  # Hello world
+features=["eyes"]  # Goodbye moon

tests/testsuite/cargo_add/overwrite_preserves_std_table/mod.rs

@@ -0,0 +1,25 @@
+use cargo_test_support::compare::assert_ui;
+use cargo_test_support::prelude::*;
+use cargo_test_support::Project;
+
+use crate::cargo_add::init_registry;
+use cargo_test_support::curr_dir;
+
+#[cargo_test]
+fn overwrite_preserves_std_table() {
+    init_registry();
+    let project = Project::from_template(curr_dir!().join("in"));
+    let project_root = project.root();
+    let cwd = &project_root;
+
+    snapbox::cmd::Command::cargo_ui()
+        .arg("add")
+        .arg_line("your-face --features nose")
+        .current_dir(cwd)
+        .assert()
+        .success()
+        .stdout_matches_path(curr_dir!().join("stdout.log"))
+        .stderr_matches_path(curr_dir!().join("stderr.log"));
+
+    assert_ui().subset_matches(curr_dir!().join("out"), &project_root);
+}

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

@@ -0,0 +1,9 @@
+[workspace]
+
+[package]
+name = "cargo-list-test-fixture"
+version = "0.0.0"
+
+[dependencies.your-face]
+version="99999.0.0"  # Hello world
+features=["eyes", "nose"]  # Goodbye moon

tests/testsuite/cargo_add/overwrite_preserves_std_table/stderr.log

@@ -0,0 +1,7 @@
+    Updating `dummy-registry` index
+      Adding your-face v99999.0.0 to dependencies.
+             Features:
+             + eyes
+             + nose
+             - ears
+             - mouth