OpenMS · t0mdavid-m · May 29, 2026 · May 29, 2026
diff --git a/js-component/dist/assets/index-264a76c5.js → js-component/dist/assets/index-3e659711.js b/js-component/dist/assets/index-264a76c5.js → js-component/dist/assets/index-3e659711.js
diff --git a/js-component/dist/index.html b/js-component/dist/index.html
@@ -5,7 +5,7 @@
     <link rel="icon" href="./favicon.ico" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>openms-streamlit-vue-component</title>
-    <script type="module" crossorigin src="./assets/index-264a76c5.js"></script>
+    <script type="module" crossorigin src="./assets/index-3e659711.js"></script>
     <link rel="stylesheet" href="./assets/index-a58b60d0.css">
   </head>
   <body>

diff --git a/src/render/render.py b/src/render/render.py
@@ -24,16 +24,23 @@ def render_component(
     # Get State
     state = state_tracker.getState()
 
+    # Cleared selections now arrive (and are stored) as `None` rather than being
+    # dropped, so the frontend can round-trip a deselect. update/filter logic uses
+    # the "key not in selection_store" convention, so drop None-valued keys for the
+    # data computation while still echoing the full state (incl. nulls) back so the
+    # frontend can clear those fields in every component.
+    active_state = {k: v for k, v in state.items() if v is not None}
+
     # Update data with current session state
-    data = update_data(data, out_components, state, additional_data, tool)
+    data = update_data(data, out_components, active_state, additional_data, tool)
 
     # Filter data based on selection
     data = filter_data(
-        data, out_components, state, additional_data, tool
+        data, out_components, active_state, additional_data, tool
     )
-    
+
     # Hash updated. filtered data
-    data['hash'] = hash_complex(data) 
+    data['hash'] = hash_complex(data)
 
     # Render component
     data['selection_store'] = state

diff --git a/tests/test_selection_clear.py b/tests/test_selection_clear.py
@@ -0,0 +1,74 @@
+"""
+Tests for the selection-clearing round-trip used by the FLASHViewer grid.
+
+Each view (Sequence View, Tag Table, Protein Table, ...) is a separate Streamlit
+component instance with its own frontend store; they share selection state only by
+round-tripping through Python's StateTracker. Clearing a selection (e.g. deselecting
+an amino acid, or switching proteoform) must therefore propagate back to every view.
+
+The frontend sends a cleared field as `null`/`None` (App.vue maps `undefined -> null`
+so the clear survives JSON serialization). These tests pin the two invariants the fix
+relies on:
+
+  1. A cleared field is echoed back as `None` so every component can clear it.
+  2. render_component strips `None`-valued keys for the data computation, preserving
+     update.py's "key not in selection_store" convention.
+
+They also document the original bug: when the cleared key was *dropped* from the
+payload entirely, the merge-only StateTracker kept echoing the stale value.
+"""
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from src.render.StateTracker import StateTracker
+
+
+def _echo_with(tracker, **overrides):
+    """Mimic a component returning the echoed state with `overrides` applied."""
+    state = tracker.getState()  # includes counter + id, like getState() -> frontend
+    state.update(overrides)
+    return state
+
+
+def _active_state(state):
+    """The view render.py passes to update/filter: None == "not selected" == absent."""
+    return {k: v for k, v in state.items() if v is not None}
+
+
+def test_selecting_a_value_round_trips():
+    tracker = StateTracker()
+    tracker.updateState(_echo_with(tracker, AApos=5))
+    assert tracker.getState()["AApos"] == 5
+    assert _active_state(tracker.getState())["AApos"] == 5
+
+
+def test_clearing_a_selection_round_trips_as_none():
+    tracker = StateTracker()
+    tracker.updateState(_echo_with(tracker, AApos=5))
+    assert tracker.getState()["AApos"] == 5
+
+    # Deselect: the frontend sends AApos=None (App.vue maps undefined -> null).
+    tracker.updateState(_echo_with(tracker, AApos=None))
+    echoed = tracker.getState()
+
+    # (1) Echoed back as None so every component clears the field locally.
+    assert echoed["AApos"] is None
+    # (2) The data-computation view treats None as absent (not selected).
+    assert "AApos" not in _active_state(echoed)
+
+
+def test_dropped_key_keeps_stale_value_regression():
+    """Pre-fix behavior: `undefined` was dropped from the payload, so the merge-only
+    StateTracker never learned about the clear and kept echoing the stale value.
+    This is exactly the bug the null-bridge (send None instead of dropping) fixes."""
+    tracker = StateTracker()
+    tracker.updateState(_echo_with(tracker, AApos=5))
+
+    payload = tracker.getState()
+    payload.pop("AApos")  # simulate the JSON-dropped undefined key
+    tracker.updateState(payload)
+
+    assert tracker.getState()["AApos"] == 5  # stale value survives -> the original bug