Respect disabled trailing whitespace removal (#58776)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
 - [x] Tests cover the new/changed behavior
 - [x] Performance impact has been considered and is acceptable

  Closes #58686

Release Notes:

- Fixed `.editorconfig` re-enabling trailing whitespace removal when Zed
settings disable it.

---------

Co-authored-by: Martin Ye <martin@zed.dev>

crates/editor/src/editor_tests.rs

@@ -16,6 +16,7 @@ use crate::{
 };
 use buffer_diff::{BufferDiff, DiffHunkSecondaryStatus, DiffHunkStatus, DiffHunkStatusKind};
 use collections::HashMap;
+use fs::Fs as _;
 use futures::{StreamExt, channel::oneshot};
 use gpui::{
     BackgroundExecutor, DismissEvent, Task, TaskExt, TestAppContext, UpdateGlobal,
@@ -17603,6 +17604,75 @@ async fn test_multiple_formatters(cx: &mut TestAppContext) {
     });
 }
 
+#[gpui::test]
+async fn test_markdown_save_respects_disabled_trailing_whitespace_removal(cx: &mut TestAppContext) {
+    init_test(cx, |settings| {
+        settings.defaults.ensure_final_newline_on_save = Some(false);
+        settings.languages.0.insert(
+            "Markdown".into(),
+            LanguageSettingsContent {
+                remove_trailing_whitespace_on_save: Some(false),
+                ..Default::default()
+            },
+        );
+    });
+
+    let fs = FakeFs::new(cx.executor());
+    fs.insert_file(
+        path!("/.editorconfig"),
+        "root = true\n[*]\ntrim_trailing_whitespace = true\n".into(),
+    )
+    .await;
+    fs.insert_file(path!("/README.md"), "".into()).await;
+
+    let project = Project::test(fs.clone(), [path!("/").as_ref()], cx).await;
+    let language_registry = project.read_with(cx, |project, _| project.languages().clone());
+    language_registry.add(markdown_lang());
+
+    let buffer = project
+        .update(cx, |project, cx| {
+            project.open_local_buffer(path!("/README.md"), cx)
+        })
+        .await
+        .unwrap();
+
+    let buffer = cx.new(|cx| MultiBuffer::singleton(buffer, cx));
+    let (editor, cx) = cx.add_window_view(|window, cx| {
+        build_editor_with_project(project.clone(), buffer, window, cx)
+    });
+    editor.update_in(cx, |editor, window, cx| {
+        editor.set_text("line with spaces  \n", window, cx)
+    });
+
+    let save = editor
+        .update_in(cx, |editor, window, cx| {
+            editor.save(
+                SaveOptions {
+                    format: true,
+                    force_format: false,
+                    autosave: false,
+                },
+                project.clone(),
+                window,
+                cx,
+            )
+        })
+        .unwrap();
+    save.await;
+
+    assert_eq!(
+        editor.update(cx, |editor, cx| editor.text(cx)),
+        "line with spaces  \n"
+    );
+    assert_eq!(
+        fs.load(path!("/README.md").as_ref())
+            .await
+            .unwrap()
+            .replace("\r\n", "\n"),
+        "line with spaces  \n"
+    );
+}
+
 #[gpui::test]
 async fn test_organize_imports_manual_trigger(cx: &mut TestAppContext) {
     init_test(cx, |settings| {

crates/language/src/language_settings.rs

@@ -695,9 +695,15 @@ fn merge_with_editorconfig(settings: &mut LanguageSettings, cfg: &EditorconfigPr
         .merge_from_option(preferred_line_length.as_ref());
     settings.tab_size.merge_from_option(tab_size.as_ref());
     settings.hard_tabs.merge_from_option(hard_tabs.as_ref());
-    settings
-        .remove_trailing_whitespace_on_save
-        .merge_from_option(remove_trailing_whitespace_on_save.as_ref());
+    // Avoid re-enabling destructive whitespace trimming when Zed settings have
+    // disabled it, e.g. for Markdown hard breaks.
+    if !matches!(remove_trailing_whitespace_on_save, Some(true))
+        || settings.remove_trailing_whitespace_on_save
+    {
+        settings
+            .remove_trailing_whitespace_on_save
+            .merge_from_option(remove_trailing_whitespace_on_save.as_ref());
+    }
     settings
         .ensure_final_newline_on_save
         .merge_from_option(ensure_final_newline_on_save.as_ref());

crates/project/tests/integration/project_tests.rs

@@ -254,7 +254,10 @@ async fn test_editorconfig_support(cx: &mut gpui::TestAppContext) {
             max_line_length = 120
         [*.js]
             tab_width = 10
+            trim_trailing_whitespace = false
             max_line_length = off
+        [*.json]
+            trim_trailing_whitespace = true
         "#,
         ".zed": {
             "settings.json": r#"{
@@ -264,6 +267,17 @@ async fn test_editorconfig_support(cx: &mut gpui::TestAppContext) {
                 "remove_trailing_whitespace_on_save": false,
                 "preferred_line_length": 64,
                 "soft_wrap": "editor_width",
+                "languages": {
+                    "JavaScript": {
+                        "remove_trailing_whitespace_on_save": true,
+                    },
+                    "JSON": {
+                        "remove_trailing_whitespace_on_save": true,
+                    },
+                    "Markdown": {
+                        "remove_trailing_whitespace_on_save": true,
+                    },
+                },
             }"#,
         },
         "a.rs": "fn a() {\n    A\n}",
@@ -293,6 +307,7 @@ async fn test_editorconfig_support(cx: &mut gpui::TestAppContext) {
             "e.rs": "fn e() {\n    E\n}",
         },
         "README.json": "tabs are better\n",
+        "README.md": "spaces are meaningful  \n",
     }));
 
     let path = dir.path();
@@ -303,6 +318,7 @@ async fn test_editorconfig_support(cx: &mut gpui::TestAppContext) {
     let language_registry = project.read_with(cx, |project, _| project.languages().clone());
     language_registry.add(js_lang());
     language_registry.add(json_lang());
+    language_registry.add(markdown_lang());
     language_registry.add(rust_lang());
 
     let worktree = project.update(cx, |project, cx| project.worktrees(cx).next().unwrap());
@@ -325,11 +341,14 @@ async fn test_editorconfig_support(cx: &mut gpui::TestAppContext) {
     let settings_d = settings_for("d/d.rs", cx).await;
     let settings_e = settings_for("e/e.rs", cx).await;
     let settings_readme = settings_for("README.json", cx).await;
+    let settings_markdown = settings_for("README.md", cx).await;
     // .editorconfig overrides .zed/settings
     assert_eq!(Some(settings_a.tab_size), NonZeroU32::new(3));
     assert_eq!(settings_a.hard_tabs, true);
     assert_eq!(settings_a.ensure_final_newline_on_save, true);
-    assert_eq!(settings_a.remove_trailing_whitespace_on_save, true);
+    // .editorconfig can disable trailing whitespace removal, but should not
+    // re-enable it when Zed settings have disabled it.
+    assert_eq!(settings_a.remove_trailing_whitespace_on_save, false);
     assert_eq!(settings_a.line_ending, LineEndingSetting::EnforceLf);
     assert_eq!(settings_a.preferred_line_length, 120);
 
@@ -348,6 +367,9 @@ async fn test_editorconfig_support(cx: &mut gpui::TestAppContext) {
 
     // "indent_size" is not set, so "tab_width" is used
     assert_eq!(Some(settings_c.tab_size), NonZeroU32::new(10));
+    assert_eq!(settings_c.remove_trailing_whitespace_on_save, false);
+    assert_eq!(settings_readme.remove_trailing_whitespace_on_save, true);
+    assert_eq!(settings_markdown.remove_trailing_whitespace_on_save, true);
 
     // When max_line_length is "off", default to .zed/settings.json
     assert_eq!(settings_b.preferred_line_length, 64);