Attempt to assign a language when a new buffer is saved

zed/src/editor.rs

@@ -4,6 +4,7 @@ mod element;
 pub mod movement;
 
 use crate::{
+    language::Language,
     settings::Settings,
     theme::Theme,
     time::ReplicaId,
@@ -449,6 +450,10 @@ impl Editor {
         }
     }
 
+    pub fn language<'a>(&self, cx: &'a AppContext) -> Option<&'a Arc<Language>> {
+        self.buffer.read(cx).language()
+    }
+
     pub fn set_placeholder_text(
         &mut self,
         placeholder_text: impl Into<Arc<str>>,

zed/src/editor/buffer.rs

@@ -714,9 +714,16 @@ impl Buffer {
         path: impl Into<Arc<Path>>,
         cx: &mut ModelContext<Self>,
     ) -> Task<Result<()>> {
+        let path = path.into();
         let handle = cx.handle();
         let text = self.visible_text.clone();
         let version = self.version.clone();
+
+        if let Some(language) = worktree.read(cx).languages().select_language(&path).cloned() {
+            self.language = Some(language);
+            self.reparse(cx);    
+        }
+
         let save_as = worktree.update(cx, |worktree, cx| {
             worktree
                 .as_local_mut()
@@ -871,7 +878,11 @@ impl Buffer {
                     cx.spawn(move |this, mut cx| async move {
                         let new_tree = parse_task.await;
                         this.update(&mut cx, move |this, cx| {
-                            let parse_again = this.version > parsed_version;
+                            let language_changed =
+                                this.language.as_ref().map_or(true, |curr_language| {
+                                    !Arc::ptr_eq(curr_language, &language)
+                                });
+                            let parse_again = this.version > parsed_version || language_changed;
                             *this.syntax_tree.lock() = Some(SyntaxTree {
                                 tree: new_tree,
                                 dirty: false,

zed/src/worktree.rs

@@ -268,6 +268,13 @@ impl Worktree {
         }
     }
 
+    pub fn languages(&self) -> &Arc<LanguageRegistry> {
+        match self {
+            Worktree::Local(worktree) => &worktree.languages,
+            Worktree::Remote(worktree) => &worktree.languages,
+        }
+    }
+
     pub fn snapshot(&self) -> Snapshot {
         match self {
             Worktree::Local(worktree) => worktree.snapshot(),