lint: standardize formatting of let-else-return statements (#2297)

`cargo fmt` doesn't handle let-else statements, so let's try to keep a
consistent style using a lint

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)

<!-- This line will get updated when the PR build summary job finishes.
-->
PR Build Summary: https://build.rerun.io/pr/2297

<!-- pr-link-docs:start -->
Docs preview: https://rerun.io/preview/c04c9b2/docs
<!-- pr-link-docs:end -->

crates/re_data_ui/src/image.rs

@@ -359,7 +359,7 @@ pub fn show_zoomed_image_region_area_outline(
 ) {
     use egui::{pos2, remap, Rect};
 
-    let Some([height, width, _]) = tensor.image_height_width_channels() else {return;};
+    let Some([height, width, _]) = tensor.image_height_width_channels() else { return; };
 
     let width = width as f32;
     let height = height as f32;

crates/re_viewer/src/app.rs

@@ -434,11 +434,11 @@ impl App {
     }
 
     fn run_time_control_command(&mut self, command: TimeControlCommand) {
-        let Some(rec_id) = &self.state.selected_rec_id else {return;};
-        let Some(rec_cfg) = self.state.recording_configs.get_mut(rec_id) else {return;};
+        let Some(rec_id) = &self.state.selected_rec_id else { return; };
+        let Some(rec_cfg) = self.state.recording_configs.get_mut(rec_id) else { return; };
         let time_ctrl = &mut rec_cfg.time_ctrl;
 
-        let Some(log_db) = self.log_dbs.get(rec_id) else { return };
+        let Some(log_db) = self.log_dbs.get(rec_id) else { return; };
         let times_per_timeline = log_db.times_per_timeline();
 
         match command {

rerun_py/src/python_bridge.rs

@@ -1171,7 +1171,7 @@ fn add_space_view(
     entity_paths: Vec<&str>,
     blueprint: Option<&PyRecordingStream>,
 ) {
-    let Some(blueprint) = get_blueprint_recording(blueprint) else { return };
+    let Some(blueprint) = get_blueprint_recording(blueprint) else { return; };
 
     let mut space_view = SpaceViewBlueprint::new(
         "Spatial".into(),
@@ -1213,7 +1213,7 @@ fn add_space_view(
 
 #[pyfunction]
 fn set_auto_space_views(enabled: bool, blueprint: Option<&PyRecordingStream>) {
-    let Some(blueprint) = get_blueprint_recording(blueprint) else { return };
+    let Some(blueprint) = get_blueprint_recording(blueprint) else { return; };
 
     // TODO(jleibs) timeless? Something else?
     let timepoint = time(true, &blueprint);

scripts/lint.py

@@ -20,6 +20,7 @@
 error_map_err_name = re.compile(r"map_err\(\|(\w+)\|")
 wasm_caps = re.compile(r"\bWASM\b")
 nb_prefix = re.compile(r"nb_")
+else_return = re.compile(r"else\s*{\s*return;?\s*};")
 
 
 def lint_line(line: str) -> Optional[str]:
@@ -63,6 +64,13 @@ def lint_line(line: str) -> Optional[str]:
         if name in ("e", "error"):
             return "Errors should be called 'err', '_err' or '_'"
 
+    m = re.search(else_return, line)
+    if m:
+        match = m.group(0)
+        if match != "else { return; };":
+            # Because cargo fmt doesn't handle let-else
+            return f"Use 'else {{ return; }};' instead of '{match}'"
+
     if wasm_caps.search(line):
         return "WASM should be written 'Wasm'"
 
@@ -94,6 +102,7 @@ def test_lint_line() -> None:
         "Wasm",
         "num_instances",
         "instances_count",
+        "let Some(foo) = bar else { return; };",
     ]
 
     should_error = [
@@ -112,6 +121,9 @@ def test_lint_line() -> None:
         "We use WASM in Rerun",
         "nb_instances",
         "inner_nb_instances",
+        "let Some(foo) = bar else {return;};",
+        "let Some(foo) = bar else {return};",
+        "let Some(foo) = bar else { return };",
     ]
 
     for line in should_pass: