fix: guard logger carriage return on empty buffer

app/logger.py

@@ -60,7 +60,7 @@ class LogInterceptor(io.TextIOWrapper):
 
             # Simple handling for cr to overwrite the last output if it isnt a full line
             # else logs just get full of progress messages
-            if isinstance(data, str) and data.startswith("\r") and not logs[-1]["m"].endswith("\n"):
+            if isinstance(data, str) and data.startswith("\r") and logs and not logs[-1]["m"].endswith("\n"):
                 logs.pop()
             logs.append(entry)
         super().write(data)

tests-unit/app_test/logger_test.py

@@ -0,0 +1,30 @@
+from collections import deque
+import io
+
+import app.logger
+from app.logger import LogInterceptor
+
+
+def make_interceptor():
+    stream = io.TextIOWrapper(io.BytesIO(), encoding="utf-8", line_buffering=True)
+    return LogInterceptor(stream), stream
+
+
+def test_carriage_return_write_with_empty_log_buffer(monkeypatch):
+    monkeypatch.setattr(app.logger, "logs", deque(maxlen=10))
+    interceptor, _stream = make_interceptor()
+
+    interceptor.write("\rprogress")
+
+    assert len(app.logger.logs) == 1
+    assert app.logger.logs[-1]["m"] == "\rprogress"
+
+
+def test_carriage_return_replaces_incomplete_log_entry(monkeypatch):
+    monkeypatch.setattr(app.logger, "logs", deque(maxlen=10))
+    interceptor, _stream = make_interceptor()
+
+    interceptor.write("progress 1")
+    interceptor.write("\rprogress 2")
+
+    assert [entry["m"] for entry in app.logger.logs] == ["\rprogress 2"]