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fix(renderer): clear paths for null children - #4052
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T4rk1n
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Fix is right, and nothing blocks merge. null (and "" / 0) is an explicit value that replaces the subtree, so the old paths have to be cleared. Only undefined means the prop wasn't returned. The test reproduces #4033 and checks both halves of it (callbacks stop after unmount, remount works).
The [] branch just above (if (!frontObj) return;, around line 291) has the same falsy check. A callback that sets options=None on a Checklist whose options[].label holds components with callbacks would leave those labels registered. Could you switch it to === undefined too? I'm fine with that being a follow-up.
| appliedProps | ||
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| if (!children) { | ||
| if (children === undefined) { |
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This also fixes children="" and children=0, which had the same stale-paths bug. Can you add a renderer test or a second case in the integration test so nobody puts back a !children check later?
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| def test_callback_returning_none_removes_child_paths_and_can_remount(dash_duo): |
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Can you follow the test_cbXXnnn_ naming used in the rest of this folder? Or move it into test_layout_paths_with_callbacks.py as the next cblp test, so it doesn't sit alone in a new file.
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| dash_duo.find_element("#toggle").click() | ||
| dash_duo.wait_for_element("#view-child") | ||
| until(lambda: "view-child" in dash_duo.redux_state_paths["strs"], timeout=3) |
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After the remount, can you also wait for the tick text in #view-child (dash_duo.wait_for_contains_text)? Having the path back doesn't show that update_view is wired to the new child again, and that's the visible symptom in the issue.
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Hi, I pushed the requested regression coverage for children values None, empty string, and zero in commit b099837; the integration cases pass locally. GitHub marked the Dash Testing and Performance Benchmarks runs as action_required without starting jobs. Could someone with admin access approve these workflow runs so CI can execute? Thanks! |
Fixes #4033.
Dash serializes a callback returning
Noneforchildrenas an explicitnullvalue. The renderer treated all falsy child values as if the callback had omitted the property, so it skipped path recomputation. Removed descendants stayed in the Redux path table, allowing their callbacks to keep firing and preventing a clean remount. The renderer now skips recomputation only when the output property is absent (undefined).Contributor Checklist
childrenvalues, includingnull.Validation
python -m pytest tests/integration/callbacks/test_children_none.py --headless -xvs— passed; the same test failed on the unmodified base when the removed child remained in the path table.python -m pytest tests/integration/callbacks/test_layout_paths_with_callbacks.py tests/integration/callbacks/test_wildcards.py -k 'cblp001 or cbwc003 or cbwc011 or cbwc014' --headless -xvs— 4 passed.npm testindash/dash-renderer— 123 passed.npm run private::lint.renderer— successful. ESLint reported three warnings in untouched files.git diff --check— passed.