debugger beta: Autoscroll to recently saved debug scenario when saving a scenario (#31528)

I added a test to this too as one of my first steps of improving
`NewSessionModal`'s test coverage.


Release Notes:

- debugger beta: Select saved debug config when opening debug.json from
`NewSessionModal`

crates/debugger_ui/src/tests/new_session_modal.rs

@@ -1,6 +1,6 @@
 use dap::DapRegistry;
 use gpui::{BackgroundExecutor, TestAppContext, VisualTestContext};
-use project::{FakeFs, Project};
+use project::{FakeFs, Fs, Project};
 use serde_json::json;
 use std::sync::Arc;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -151,6 +151,106 @@ async fn test_debug_session_substitutes_variables_and_relativizes_paths(
     }
 }
 
+#[gpui::test]
+async fn test_save_debug_scenario_to_file(executor: BackgroundExecutor, cx: &mut TestAppContext) {
+    init_test(cx);
+
+    let fs = FakeFs::new(executor.clone());
+    fs.insert_tree(
+        path!("/project"),
+        json!({
+            "main.rs": "fn main() {}"
+        }),
+    )
+    .await;
+
+    let project = Project::test(fs.clone(), [path!("/project").as_ref()], cx).await;
+    let workspace = init_test_workspace(&project, cx).await;
+    let cx = &mut VisualTestContext::from_window(*workspace, cx);
+
+    workspace
+        .update(cx, |workspace, window, cx| {
+            crate::new_session_modal::NewSessionModal::show(workspace, window, cx);
+        })
+        .unwrap();
+
+    cx.run_until_parked();
+
+    let modal = workspace
+        .update(cx, |workspace, _, cx| {
+            workspace.active_modal::<crate::new_session_modal::NewSessionModal>(cx)
+        })
+        .unwrap()
+        .expect("Modal should be active");
+
+    modal.update_in(cx, |modal, window, cx| {
+        modal.set_custom("/project/main", "/project", false, window, cx);
+        modal.save_scenario(window, cx);
+    });
+
+    cx.executor().run_until_parked();
+
+    let debug_json_content = fs
+        .load(path!("/project/.zed/debug.json").as_ref())
+        .await
+        .expect("debug.json should exist");
+
+    let expected_content = vec![
+        "[",
+        "  {",
+        r#"    "adapter": "fake-adapter","#,
+        r#"    "label": "main (fake-adapter)","#,
+        r#"    "request": "launch","#,
+        r#"    "program": "/project/main","#,
+        r#"    "cwd": "/project","#,
+        r#"    "args": [],"#,
+        r#"    "env": {}"#,
+        "  }",
+        "]",
+    ];
+
+    let actual_lines: Vec<&str> = debug_json_content.lines().collect();
+    pretty_assertions::assert_eq!(expected_content, actual_lines);
+
+    modal.update_in(cx, |modal, window, cx| {
+        modal.set_custom("/project/other", "/project", true, window, cx);
+        modal.save_scenario(window, cx);
+    });
+
+    cx.executor().run_until_parked();
+
+    let debug_json_content = fs
+        .load(path!("/project/.zed/debug.json").as_ref())
+        .await
+        .expect("debug.json should exist after second save");
+
+    let expected_content = vec![
+        "[",
+        "  {",
+        r#"    "adapter": "fake-adapter","#,
+        r#"    "label": "main (fake-adapter)","#,
+        r#"    "request": "launch","#,
+        r#"    "program": "/project/main","#,
+        r#"    "cwd": "/project","#,
+        r#"    "args": [],"#,
+        r#"    "env": {}"#,
+        "  },",
+        "  {",
+        r#"    "adapter": "fake-adapter","#,
+        r#"    "label": "other (fake-adapter)","#,
+        r#"    "request": "launch","#,
+        r#"    "program": "/project/other","#,
+        r#"    "cwd": "/project","#,
+        r#"    "args": [],"#,
+        r#"    "env": {}"#,
+        "  }",
+        "]",
+    ];
+
+    let actual_lines: Vec<&str> = debug_json_content.lines().collect();
+    pretty_assertions::assert_eq!(expected_content, actual_lines);
+}
+
 #[gpui::test]
 async fn test_dap_adapter_config_conversion_and_validation(cx: &mut TestAppContext) {
     init_test(cx);