Allow dynamic changes to `st.pydeck_chart` parameters when `key` is provided by lukasmasuch · Pull Request #13703 · streamlit/streamlit

lukasmasuch · 2026-01-27T02:20:41Z

Describe your changes

This PR enables st.pydeck_chart to preserve selection state when map data or parameters change, when a user provides a key parameter. Selection state now persists across data updates, similar to st.vega_lite_chart.

Backend Change: Set key_as_main_identity={"selection_mode"} so the element ID depends only on the selection mode, not the spec.

Frontend Changes:

Add selection sanitization to remove orphaned indices when data shrinks or layers are removed
Improve the anyLayersHaveSelection check to validate indices before applying dimming
Add proper React key in ElementNodeRenderer matching ArrowVegaLiteChart pattern

Testing Plan

Tested locally that TypeScript compiles without errors
Manual testing recommended: verify selection persists when data updates with key="my_map"
Verify backward compatibility: selection resets without a key or when selection_mode changes
Edge case: verify no visual glitches when data shrinks (orphaned indices are sanitized)

Contribution License Agreement

By submitting this pull request you agree that all contributions to this project are made under the Apache 2.0 license.

…meter When a user provides a `key` parameter to st.pydeck_chart with selections enabled, the element ID now remains stable across data/spec changes, allowing selection state to persist similar to st.vega_lite_chart. Changes: - Backend: Set key_as_main_identity={"selection_mode"} to use only the selection mode for ID computation when key is provided - Frontend: Add selection sanitization useEffect to remove orphaned indices when data shrinks or layers are removed - Frontend: Improve anyLayersHaveSelection check to validate indices before applying dimming, preventing visual glitches - Frontend: Add proper React key in ElementNodeRenderer matching ArrowVegaLiteChart pattern Co-Authored-By: Claude <[email protected]>

snyk-io · 2026-01-27T02:20:50Z

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github-actions · 2026-01-27T02:20:56Z

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Copilot

Pull request overview

This PR implements selection state preservation for st.pydeck_chart when users provide a key parameter, matching the established pattern used by st.vega_lite_chart and st.dataframe. The implementation allows map selections to persist across data updates without forcing a full reset.

Changes:

Backend: Modified element ID computation to use key_as_main_identity={"selection_mode"}, making element identity stable when a key is provided
Frontend: Added selection sanitization logic to remove orphaned indices when data shrinks or layers are removed
Frontend: Enhanced the anyLayersHaveSelection validation to prevent visual glitches with stale selections
Frontend: Added React key pattern in ElementNodeRenderer consistent with ArrowVegaLiteChart

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
`lib/streamlit/elements/deck_gl_json_chart.py`	Changed `key_as_main_identity` from `False` to `{"selection_mode"}` to preserve element ID across spec changes when a key is provided
`frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx`	Added sanitization useEffect to clean orphaned selections and improved selection validation logic
`frontend/lib/src/components/core/Block/ElementNodeRenderer.tsx`	Added conditional React key based on element ID, matching the ArrowVegaLiteChart pattern
`dynamic-pydeck-chart-opus.md`	Documentation file providing implementation analysis and context (not production code)
`dynamic-pydeck-chart-codex.md`	Documentation file with technical deep-dive (not production code)

frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx

lib/streamlit/elements/deck_gl_json_chart.py

cursor

Cursor Bugbot has reviewed your changes and found 3 potential issues.

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dynamic-pydeck-chart-codex.md

frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx

- Add Python unit tests for element ID stability with key - Add E2E test for selection preservation when data updates - Add selection sanitization effect for orphaned indices - Add smarter dimming check to validate indices before applying - Remove planning documents Co-Authored-By: Claude <[email protected]>

lib/tests/streamlit/elements/pydeck_test.py

- Fix non-array layer data handling: preserve selections for layers with URL strings, GeoJSON objects, or undefined data instead of clearing them - Extract duplicated layer data lengths logic into getLayerDataLengths helper - Remove data.selection from useEffect dependency array to avoid unnecessary re-executions (only sanitize when spec changes) - Fix unit tests to properly verify element ID stability with same key using mock to bypass duplicate key restriction Co-Authored-By: Claude <[email protected]>

github-actions · 2026-01-27T12:37:52Z

📈 Frontend coverage change detected

The frontend unit test (vitest) coverage has increased by 0.1300%

Current PR: 86.4000% (13626 lines, 1853 missed)
Latest develop: 86.2700% (13562 lines, 1862 missed)

🎉 Great job on improving test coverage!

📊 View detailed coverage comparison

github-actions · 2026-01-27T12:40:14Z

Summary

This PR makes st.pydeck_chart selection state stable across spec changes when a key is provided, adds frontend sanitization to drop orphaned selection indices, and aligns DeckGL rendering with widget-style React keys. It also adds a dynamic data e2e scenario and Python unit tests for element ID stability.

Code Quality

The new selection sanitization is cleanly encapsulated, but it only updates client-side state. Because updates are marked fromUi: false, the backend selection can remain stale on the rerun that introduces a data shrink or layer removal, which can diverge from what the UI displays and what app code sees.

  useEffect(() => {
    if (!isSelectionModeActivated || !parsedPydeckJson.layers) {
      return
    }
    // ...
    if (changed) {
      setSelection({
        fromUi: false,
        value: { selection: { indices: newIndices, objects: newObjects } },
      })
    }
    // ...
  }, [parsedPydeckJson, isSelectionModeActivated, setSelection])

            pydeck_proto.id = compute_and_register_element_id(
                "deck_gl_json_chart",
                user_key=key,
                # When a key is provided, only selection_mode affects the element ID.
                # This allows selection state to persist across data/spec changes.
                # Note: This can lead to orphaned selections if data length shrinks,
                # but the frontend handles this by sanitizing invalid indices.
                key_as_main_identity={"selection_mode"},

Test Coverage

The new e2e test verifies selection persistence on data updates, but it does not cover the orphaned-index cases the sanitization logic targets (data shrink or layer removal), and it lacks a “must NOT happen” assertion per the e2e guidelines.

@pytest.mark.only_browser("chromium")
@pytest.mark.flaky(reruns=4)
def test_pydeck_chart_selection_preserved_when_data_updates(app: Page):
    """
    Test that selection state is preserved when data updates and a key is provided.
    This tests the key_as_main_identity={"selection_mode"} behavior.
    """
    _select_chart_type(app, "dynamic")
    wait_for_chart(app)
    # ...
    # Selection should still be preserved because key is provided
    expect_prefixed_markdown(app, markdown_prefix, FIRST_POINT_SELECTION)
    expect_prefixed_markdown(app, markdown_prefix_session_state, FIRST_POINT_SELECTION)

Backwards Compatibility

Behavior changes are gated behind providing key and enabling selections; the non-keyed path continues to reset selection on spec changes. No protobuf changes are introduced.

Security & Risk

No security issues identified. The main risk is stale selection indices when data shrinks, which can lead to UI/backend divergence or out-of-range indexing in app code on the rerun that introduces the data change.

Recommendations

Add a test case that shrinks data or removes a layer to exercise the sanitization logic and include a “must NOT happen” assertion (e.g., no dimming or no stale selection after update).
Consider syncing the sanitized selection back to the backend or documenting that selection objects may be stale after data updates, especially when data shrinks.
Align the new Python tests with the unit test guide by adding type annotations and avoiding direct MagicMock/patch imports if feasible.

Verdict

APPROVED: Changes are solid and behavior is well-motivated; only follow-up coverage/consistency improvements are recommended.

This is an automated AI review using gpt-5.2-codex-high. Please verify the feedback and use your judgment.

Add comprehensive tests for: - Clear selection button rendering in DeckGlJsonChart - Selection sanitization in useDeckGl hook (layer removal, data shrinking, URL data preservation) - PydeckSelectionSerde serialization/deserialization - parse_selection_mode function validation - Callback handling with on_select parameter Co-Authored-By: Claude <[email protected]>

Co-Authored-By: Claude (claude-opus-4-5) <[email protected]>

frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx

The hasUnknownLayerId flag was incorrectly preserving orphaned selections when any layer lacked an ID. Now only preserve when ALL layers lack IDs (layerData is empty), allowing proper cleanup of non-existent layer selections in mixed scenarios. Co-Authored-By: Claude (claude-opus-4-5) <[email protected]>

sfc-gh-lwilby · 2026-01-29T14:33:35Z

frontend/lib/src/components/elements/DeckGlJsonChart/DeckGlJsonChart.test.tsx

    }
  )

+  it("should render clear selection button when there is an active selection and not disabled", async () => {


Is this test related, or is it just opportunistically adding more test coverage?

It's partly related to the selection state itself, which we are touching in this PR, but I also requested Claude to add some more tests around the selection logic (which was previously a but undercovered)

sfc-gh-lwilby · 2026-01-29T14:50:22Z

frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx

+      parsedPydeckJson.layers
+    )
+
+    // Filter out orphaned selections


Maybe make this into a separate function for readability/testing?

Sounds good, extracted it!

sfc-gh-lwilby · 2026-01-29T14:53:28Z

frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx

+        continue
+      }
+
+      const objects = data.selection.objects[layerId] || []


Also this block could be a small function.

Updated as well 👍

sfc-gh-lwilby · 2026-01-29T14:58:57Z

frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx

+      const { layerData } = getLayerDataInfo(jsonCopy.layers)
+
+      // Only consider a selection valid if the layer exists and has at least one
+      // index within the current data length. This prevents dimming when selection


I'm not very familiar with this element, is dimming referring to changing the node's appearance to unselected?

Yes, when a selection is active, unselected points are dimmed by reducing their opacity to 40%, making selected points stand out. I've updated the comment to clarify this behavior.

sfc-gh-lwilby · 2026-01-29T15:00:27Z

lib/tests/streamlit/elements/pydeck_test.py

+
+
+class PydeckSelectionSerdeTest(DeltaGeneratorTestCase):
+    """Test PydeckSelectionSerde serialization and deserialization."""


Are these opportunistic test coverage? Or related to the changes?

Yep, see the other comment

sfc-gh-lwilby · 2026-01-29T15:10:41Z

lib/tests/streamlit/elements/pydeck_test.py

+        assert "Selection mode must be a single value" in str(e.value)
+
+
+class PydeckCallbackTest(DeltaGeneratorTestCase):


I guess this one also, is opportunistic added coverage for callbacks and not directly related?

Indirectly related since it covers the selection logic itself. So a bit more opportunistic to fill in missing coverage for selection logic on pydeck_chart.

Extract selection sanitization logic into reusable helper functions for better readability and testability: - sanitizeSelection(): main orchestration function - filterValidIndicesForLayer(): index validation for array data Also clarify "dimming" comment to explain it reduces opacity to 40%. Co-Authored-By: Claude (claude-opus-4-5) <[email protected]>

Copilot AI review requested due to automatic review settings January 27, 2026 02:20

Copilot started reviewing on behalf of lukasmasuch January 27, 2026 02:21 View session

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frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx Outdated Show resolved Hide resolved

frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx Outdated Show resolved Hide resolved

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lib/tests/streamlit/elements/pydeck_test.py Show resolved Hide resolved

lukasmasuch added change:feature PR contains new feature or enhancement implementation impact:users PR changes affect end users security-assessment-completed labels Jan 27, 2026

lukasmasuch changed the title ~~Support selection state preservation in st.pydeck_chart with key~~ Allow dynamic changes to st.pydeck_chart parameters when key is provided Jan 27, 2026

lukasmasuch and others added 4 commits January 27, 2026 14:30

Refine DeckGL selection sanitization

0909826

Tidy DeckGL id checks and hook docs

fec5947

Add useEffect import for DeckGL hook

521689d

Co-Authored-By: Claude (claude-opus-4-5) <[email protected]>

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frontend/lib/src/components/elements/DeckGlJsonChart/useDeckGl.tsx Outdated Show resolved Hide resolved

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lukasmasuch and others added 2 commits January 29, 2026 21:45

Merge branch 'develop' into lukasmasuch/pydeck-key-selection

0309721

sfc-gh-lwilby approved these changes Jan 29, 2026

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lukasmasuch merged commit 6f66a1c into develop Jan 29, 2026
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lukasmasuch deleted the lukasmasuch/pydeck-key-selection branch January 29, 2026 22:18



		class PydeckSelectionSerdeTest(DeltaGeneratorTestCase):
		"""Test PydeckSelectionSerde serialization and deserialization."""

		assert "Selection mode must be a single value" in str(e.value)


		class PydeckCallbackTest(DeltaGeneratorTestCase):

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lukasmasuch commented Jan 27, 2026

Describe your changes

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