Introduce code generation (#2901)

![CleanShot 2023-08-28 at 12 24
36@2x](https://github.com/zed-industries/zed/assets/482957/f97cb399-1ac2-4fa9-94a7-137d1eec711c)


Release Notes:

- Added a new "Inline Assist" feature that lets you transform a
selection or generate new code at the cursor location by hitting
`ctrl-enter`.

crates/editor/src/editor.rs

@@ -1635,6 +1635,15 @@ impl Editor {
         self.read_only = read_only;
     }
 
+    pub fn set_field_editor_style(
+        &mut self,
+        style: Option<Arc<GetFieldEditorTheme>>,
+        cx: &mut ViewContext<Self>,
+    ) {
+        self.get_field_editor_theme = style;
+        cx.notify();
+    }
+
     pub fn replica_id_map(&self) -> Option<&HashMap<ReplicaId, ReplicaId>> {
         self.replica_id_mapping.as_ref()
     }
@@ -4989,6 +4998,9 @@ impl Editor {
             self.unmark_text(cx);
             self.refresh_copilot_suggestions(true, cx);
             cx.emit(Event::Edited);
+            cx.emit(Event::TransactionUndone {
+                transaction_id: tx_id,
+            });
         }
     }
 
@@ -8428,6 +8440,9 @@ pub enum Event {
         local: bool,
         autoscroll: bool,
     },
+    TransactionUndone {
+        transaction_id: TransactionId,
+    },
     Closed,
 }
 
@@ -8468,7 +8483,7 @@ impl View for Editor {
         "Editor"
     }
 
-    fn focus_in(&mut self, _: AnyViewHandle, cx: &mut ViewContext<Self>) {
+    fn focus_in(&mut self, focused: AnyViewHandle, cx: &mut ViewContext<Self>) {
         if cx.is_self_focused() {
             let focused_event = EditorFocused(cx.handle());
             cx.emit(Event::Focused);
@@ -8476,7 +8491,7 @@ impl View for Editor {
         }
         if let Some(rename) = self.pending_rename.as_ref() {
             cx.focus(&rename.editor);
-        } else {
+        } else if cx.is_self_focused() || !focused.is::<Editor>() {
             if !self.focused {
                 self.blink_manager.update(cx, BlinkManager::enable);
             }

crates/editor/src/multi_buffer.rs

@@ -617,6 +617,42 @@ impl MultiBuffer {
         }
     }
 
+    pub fn merge_transactions(
+        &mut self,
+        transaction: TransactionId,
+        destination: TransactionId,
+        cx: &mut ModelContext<Self>,
+    ) {
+        if let Some(buffer) = self.as_singleton() {
+            buffer.update(cx, |buffer, _| {
+                buffer.merge_transactions(transaction, destination)
+            });
+        } else {
+            if let Some(transaction) = self.history.forget(transaction) {
+                if let Some(destination) = self.history.transaction_mut(destination) {
+                    for (buffer_id, buffer_transaction_id) in transaction.buffer_transactions {
+                        if let Some(destination_buffer_transaction_id) =
+                            destination.buffer_transactions.get(&buffer_id)
+                        {
+                            if let Some(state) = self.buffers.borrow().get(&buffer_id) {
+                                state.buffer.update(cx, |buffer, _| {
+                                    buffer.merge_transactions(
+                                        buffer_transaction_id,
+                                        *destination_buffer_transaction_id,
+                                    )
+                                });
+                            }
+                        } else {
+                            destination
+                                .buffer_transactions
+                                .insert(buffer_id, buffer_transaction_id);
+                        }
+                    }
+                }
+            }
+        }
+    }
+
     pub fn finalize_last_transaction(&mut self, cx: &mut ModelContext<Self>) {
         self.history.finalize_last_transaction();
         for BufferState { buffer, .. } in self.buffers.borrow().values() {
@@ -788,6 +824,20 @@ impl MultiBuffer {
         None
     }
 
+    pub fn undo_transaction(&mut self, transaction_id: TransactionId, cx: &mut ModelContext<Self>) {
+        if let Some(buffer) = self.as_singleton() {
+            buffer.update(cx, |buffer, cx| buffer.undo_transaction(transaction_id, cx));
+        } else if let Some(transaction) = self.history.remove_from_undo(transaction_id) {
+            for (buffer_id, transaction_id) in &transaction.buffer_transactions {
+                if let Some(BufferState { buffer, .. }) = self.buffers.borrow().get(buffer_id) {
+                    buffer.update(cx, |buffer, cx| {
+                        buffer.undo_transaction(*transaction_id, cx)
+                    });
+                }
+            }
+        }
+    }
+
     pub fn stream_excerpts_with_context_lines(
         &mut self,
         buffer: ModelHandle<Buffer>,
@@ -2316,6 +2366,16 @@ impl MultiBufferSnapshot {
         }
     }
 
+    pub fn prev_non_blank_row(&self, mut row: u32) -> Option<u32> {
+        while row > 0 {
+            row -= 1;
+            if !self.is_line_blank(row) {
+                return Some(row);
+            }
+        }
+        None
+    }
+
     pub fn line_len(&self, row: u32) -> u32 {
         if let Some((_, range)) = self.buffer_line_for_row(row) {
             range.end.column - range.start.column
@@ -3347,6 +3407,35 @@ impl History {
         }
     }
 
+    fn forget(&mut self, transaction_id: TransactionId) -> Option<Transaction> {
+        if let Some(ix) = self
+            .undo_stack
+            .iter()
+            .rposition(|transaction| transaction.id == transaction_id)
+        {
+            Some(self.undo_stack.remove(ix))
+        } else if let Some(ix) = self
+            .redo_stack
+            .iter()
+            .rposition(|transaction| transaction.id == transaction_id)
+        {
+            Some(self.redo_stack.remove(ix))
+        } else {
+            None
+        }
+    }
+
+    fn transaction_mut(&mut self, transaction_id: TransactionId) -> Option<&mut Transaction> {
+        self.undo_stack
+            .iter_mut()
+            .find(|transaction| transaction.id == transaction_id)
+            .or_else(|| {
+                self.redo_stack
+                    .iter_mut()
+                    .find(|transaction| transaction.id == transaction_id)
+            })
+    }
+
     fn pop_undo(&mut self) -> Option<&mut Transaction> {
         assert_eq!(self.transaction_depth, 0);
         if let Some(transaction) = self.undo_stack.pop() {
@@ -3367,6 +3456,16 @@ impl History {
         }
     }
 
+    fn remove_from_undo(&mut self, transaction_id: TransactionId) -> Option<&Transaction> {
+        let ix = self
+            .undo_stack
+            .iter()
+            .rposition(|transaction| transaction.id == transaction_id)?;
+        let transaction = self.undo_stack.remove(ix);
+        self.redo_stack.push(transaction);
+        self.redo_stack.last()
+    }
+
     fn group(&mut self) -> Option<TransactionId> {
         let mut count = 0;
         let mut transactions = self.undo_stack.iter();