Allow creating entries when nothing is selected in the project panel (#29336)

Closes https://github.com/zed-industries/zed/issues/29249

Release Notes:

- Allowed creating entries when nothing is selected in the project panel

crates/project_panel/src/project_panel.rs

@@ -1389,11 +1389,29 @@ impl ProjectPanel {
     }
 
     fn add_entry(&mut self, is_dir: bool, window: &mut Window, cx: &mut Context<Self>) {
-        if let Some(SelectedEntry {
+        let Some((worktree_id, entry_id)) = self
+            .selection
+            .map(|entry| (entry.worktree_id, entry.entry_id))
+            .or_else(|| {
+                let entry_id = self.last_worktree_root_id?;
+                let worktree_id = self
+                    .project
+                    .read(cx)
+                    .worktree_for_entry(entry_id, cx)?
+                    .read(cx)
+                    .id();
+
+                self.selection = Some(SelectedEntry {
                     worktree_id,
                     entry_id,
-        }) = self.selection
-        {
+                });
+
+                Some((worktree_id, entry_id))
+            })
+        else {
+            return;
+        };
+
         let directory_id;
         let new_entry_id = self.resolve_entry(entry_id);
         if let Some((worktree, expanded_dir_ids)) = self
@@ -1427,6 +1445,7 @@ impl ProjectPanel {
         } else {
             return;
         };
+
         self.marked_entries.clear();
         self.edit_state = Some(EditState {
             worktree_id,
@@ -1446,7 +1465,6 @@ impl ProjectPanel {
         self.autoscroll(cx);
         cx.notify();
     }
-    }
 
     fn unflatten_entry_id(&self, leaf_entry_id: ProjectEntryId) -> ProjectEntryId {
         if let Some(ancestors) = self.ancestors.get(&leaf_entry_id) {

crates/project_panel/src/project_panel_tests.rs

@@ -4948,6 +4948,71 @@ async fn test_collapse_all_for_entry(cx: &mut gpui::TestAppContext) {
     }
 }
 
+#[gpui::test]
+async fn test_create_entries_without_selection(cx: &mut gpui::TestAppContext) {
+    init_test(cx);
+
+    let fs = FakeFs::new(cx.executor().clone());
+    fs.insert_tree(
+        path!("/root"),
+        json!({
+            "dir1": {
+                "file1.txt": "",
+            },
+        }),
+    )
+    .await;
+
+    let project = Project::test(fs.clone(), [path!("/root").as_ref()], cx).await;
+    let workspace = cx.add_window(|window, cx| Workspace::test_new(project.clone(), window, cx));
+    let cx = &mut VisualTestContext::from_window(*workspace, cx);
+
+    let panel = workspace
+        .update(cx, |workspace, window, cx| {
+            let panel = ProjectPanel::new(workspace, window, cx);
+            workspace.add_panel(panel.clone(), window, cx);
+            panel
+        })
+        .unwrap();
+
+    #[rustfmt::skip]
+    assert_eq!(
+        visible_entries_as_strings(&panel, 0..20, cx),
+        &[
+            separator!("v root"),
+            separator!("    > dir1"),
+        ],
+        "Initial state with nothing selected"
+    );
+
+    panel.update_in(cx, |panel, window, cx| {
+        panel.new_file(&NewFile, window, cx);
+    });
+    panel.update_in(cx, |panel, window, cx| {
+        assert!(panel.filename_editor.read(cx).is_focused(window));
+    });
+    panel
+        .update_in(cx, |panel, window, cx| {
+            panel.filename_editor.update(cx, |editor, cx| {
+                editor.set_text("hello_from_no_selections", window, cx)
+            });
+            panel.confirm_edit(window, cx).unwrap()
+        })
+        .await
+        .unwrap();
+
+    #[rustfmt::skip]
+    assert_eq!(
+        visible_entries_as_strings(&panel, 0..20, cx),
+        &[
+            separator!("v root"),
+            separator!("    > dir1"),
+            separator!("      hello_from_no_selections  <== selected  <== marked"),
+        ],
+        "A new file is created under the root directory"
+    );
+}
+
 fn select_path(panel: &Entity<ProjectPanel>, path: impl AsRef<Path>, cx: &mut VisualTestContext) {
     let path = path.as_ref();
     panel.update(cx, |panel, cx| {