fix: mo.status.progress_bar correctly handles range step

marimo/_plugins/stateless/status/_progress.py

@@ -389,7 +389,6 @@ def __init__(
         self.completion_subtitle = completion_subtitle
         self.remove_on_exit = remove_on_exit
         self.disabled = disabled
-        self.step: int = 1
         self.collection = collection
         self._is_async = isinstance(collection, AsyncIterable)
 
@@ -404,9 +403,6 @@ def __init__(
                         "A `total` must be provided."
                     )
 
-            if isinstance(collection, range):
-                self.step = cast(range, collection).step
-
         elif total is None:
             raise ValueError(
                 "`total` is required when using as a context manager"
@@ -438,7 +434,7 @@ def __iter__(self) -> Iterator[S]:
             for item in cast(Iterable[S], self.collection):
                 yield item
                 if not self.disabled:
-                    self.progress.update(increment=self.step)
+                    self.progress.update(increment=1)
         finally:
             self._finish()
 
@@ -458,7 +454,7 @@ async def __aiter__(self) -> AsyncIterator[S]:
             async for item in cast(AsyncIterable[S], self.collection):
                 yield item
                 if not self.disabled:
-                    self.progress.update(increment=self.step)
+                    self.progress.update(increment=1)
         finally:
             self._finish()
 

tests/_plugins/stateless/status/test_progress.py

@@ -9,6 +9,7 @@
 
 from marimo._plugins.stateless.status._progress import (
     _Progress,
+    ProgressBar,
     progress_bar,
     spinner,
 )
@@ -247,3 +248,89 @@ async def test_progress_async_for_loop_without_collection_error():
     ):
         async for _ in progress_bar(total=1):
             pass
+
+
+# Bug fix: mo.status.progress_bar should use the step property of 'range'
+# https://github.com/marimo-team/marimo/issues/9575
+
+
+@patch("marimo._runtime.output._output.flush")
+@patch("marimo._runtime.output._output.append")
+def test_progress_bar_range_with_step(mock_append, mock_flush):
+    """progress_bar with range(0, 10, 2) should yield 5 items and increment by 1."""
+    del mock_flush
+
+    captured = [None]
+
+    def capture_progress(obj):
+        if isinstance(obj, ProgressBar):
+            captured[0] = obj
+
+    mock_append.side_effect = capture_progress
+
+    result = list(progress_bar(range(0, 10, 2)))
+    assert result == [0, 2, 4, 6, 8]
+    assert captured[0] is not None
+    # Each iteration should increment by 1, not by the range step
+    assert captured[0].current == 5
+
+
+@patch("marimo._runtime.output._output.flush")
+@patch("marimo._runtime.output._output.append")
+def test_progress_bar_range_no_step(mock_append, mock_flush):
+    """progress_bar with range(10) should still work correctly."""
+    del mock_flush
+
+    captured = [None]
+
+    def capture_progress(obj):
+        if isinstance(obj, ProgressBar):
+            captured[0] = obj
+
+    mock_append.side_effect = capture_progress
+
+    result = list(progress_bar(range(10)))
+    assert result == [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+    assert captured[0] is not None
+    assert captured[0].current == 10
+
+
+@patch("marimo._runtime.output._output.flush")
+@patch("marimo._runtime.output._output.append")
+def test_progress_bar_range_custom_step(mock_append, mock_flush):
+    """progress_bar with range(5, 20, 3) should yield 5 items."""
+    del mock_flush
+
+    captured = [None]
+
+    def capture_progress(obj):
+        if isinstance(obj, ProgressBar):
+            captured[0] = obj
+
+    mock_append.side_effect = capture_progress
+
+    result = list(progress_bar(range(5, 20, 3)))
+    assert result == [5, 8, 11, 14, 17]
+    assert captured[0] is not None
+    assert captured[0].current == 5
+
+
+@patch("marimo._runtime.output._output.flush")
+@patch("marimo._runtime.output._output.append")
+def test_progress_bar_range_negative_step(mock_append, mock_flush):
+    """progress_bar with range(10, 0, -2) should yield 5 items."""
+    del mock_flush
+
+    captured = [None]
+
+    def capture_progress(obj):
+        if isinstance(obj, ProgressBar):
+            captured[0] = obj
+
+    mock_append.side_effect = capture_progress
+
+    result = list(progress_bar(range(10, 0, -2)))
+    assert result == [10, 8, 6, 4, 2]
+    assert captured[0] is not None
+    assert captured[0].current == 5
+