Allow editor to be saved when in multi-buffer mode

Also, this commit enables the customization of the title in a multi-buffer.
When specified, it will take precedence over a filename (or "untitled").

crates/diagnostics/src/diagnostics.rs

@@ -28,7 +28,7 @@ use std::{
     sync::Arc,
 };
 use util::TryFutureExt;
-use workspace::{ItemNavHistory, Workspace};
+use workspace::{ItemNavHistory, ItemViewHandle as _, Workspace};
 
 action!(Deploy);
 action!(OpenExcerpts);
@@ -573,7 +573,7 @@ impl workspace::ItemView for ProjectDiagnosticsEditor {
     }
 
     fn save(&mut self, cx: &mut ViewContext<Self>) -> Task<Result<()>> {
-        self.excerpts.update(cx, |excerpts, cx| excerpts.save(cx))
+        self.editor.save(cx)
     }
 
     fn can_save_as(&self, _: &AppContext) -> bool {

crates/editor/src/editor.rs

@@ -883,16 +883,7 @@ impl Editor {
     }
 
     pub fn title(&self, cx: &AppContext) -> String {
-        let filename = self
+        self.buffer().read(cx).title(cx)
-            .buffer()
-            .read(cx)
-            .file(cx)
-            .map(|file| file.file_name(cx));
-        if let Some(name) = filename {
-            name.to_string_lossy().into()
-        } else {
-            "untitled".into()
-        }
     }
 
     pub fn snapshot(&mut self, cx: &mut MutableAppContext) -> EditorSnapshot {
@@ -2120,6 +2111,7 @@ impl Editor {
         };
         let action_ix = action_ix.unwrap_or(actions_menu.selected_item);
         let action = actions_menu.actions.get(action_ix)?.clone();
+        let title = action.lsp_action.title.clone();
         let buffer = actions_menu.buffer;
         let replica_id = editor.read(cx).replica_id(cx);
 
@@ -2131,7 +2123,7 @@ impl Editor {
 
             let mut ranges_to_highlight = Vec::new();
             let excerpt_buffer = cx.add_model(|cx| {
-                let mut multibuffer = MultiBuffer::new(replica_id);
+                let mut multibuffer = MultiBuffer::new(replica_id).with_title(title);
                 for (buffer, transaction) in &project_transaction.0 {
                     let snapshot = buffer.read(cx).snapshot();
                     ranges_to_highlight.extend(
@@ -2152,7 +2144,12 @@ impl Editor {
                 let editor = workspace.open_item(MultiBufferItemHandle(excerpt_buffer), cx);
                 if let Some(editor) = editor.act_as::<Self>(cx) {
                     editor.update(cx, |editor, cx| {
-                        editor.highlight_ranges::<Self>(ranges_to_highlight, Color::blue(), cx);
+                        let settings = (editor.build_settings)(cx);
+                        editor.highlight_ranges::<Self>(
+                            ranges_to_highlight,
+                            settings.style.highlighted_line_background,
+                            cx,
+                        );
                     });
                 }
             });

crates/editor/src/items.rs

@@ -218,7 +218,7 @@ impl ItemView for Editor {
     }
 
     fn can_save(&self, cx: &AppContext) -> bool {
-        self.project_path(cx).is_some()
+        !self.buffer().read(cx).is_singleton() || self.project_path(cx).is_some()
     }
 
     fn save(&mut self, cx: &mut ViewContext<Self>) -> Task<Result<()>> {
@@ -235,8 +235,8 @@ impl ItemView for Editor {
         })
     }
 
-    fn can_save_as(&self, _: &AppContext) -> bool {
+    fn can_save_as(&self, cx: &AppContext) -> bool {
-        true
+        self.buffer().read(cx).is_singleton()
     }
 
     fn save_as(

crates/editor/src/multi_buffer.rs

@@ -39,6 +39,7 @@ pub struct MultiBuffer {
     singleton: bool,
     replica_id: ReplicaId,
     history: History,
+    title: Option<String>,
 }
 
 struct History {
@@ -167,9 +168,15 @@ impl MultiBuffer {
                 transaction_depth: 0,
                 group_interval: Duration::from_millis(300),
             },
+            title: Default::default(),
         }
     }
 
+    pub fn with_title(mut self, title: String) -> Self {
+        self.title = Some(title);
+        self
+    }
+
     pub fn singleton(buffer: ModelHandle<Buffer>, cx: &mut ModelContext<Self>) -> Self {
         let mut this = Self::new(buffer.read(cx).replica_id());
         this.singleton = true;
@@ -227,6 +234,10 @@ impl MultiBuffer {
         }
     }
 
+    pub fn is_singleton(&self) -> bool {
+        self.singleton
+    }
+
     pub fn subscribe(&mut self) -> Subscription {
         self.subscriptions.subscribe()
     }
@@ -945,6 +956,16 @@ impl MultiBuffer {
         self.as_singleton()?.read(cx).file()
     }
 
+    pub fn title(&self, cx: &AppContext) -> String {
+        if let Some(title) = self.title.clone() {
+            title
+        } else if let Some(file) = self.file(cx) {
+            file.file_name(cx).to_string_lossy().into()
+        } else {
+            "untitled".into()
+        }
+    }
+
     #[cfg(test)]
     pub fn is_parsing(&self, cx: &AppContext) -> bool {
         self.as_singleton().unwrap().read(cx).is_parsing()