inventory/docs/fix-multi-select.md

Solution: Keeping Dropdowns Open During Multiple Selections

The Problem

When implementing a multi-select dropdown in React, a common issue occurs:

1. You select an item in the dropdown
2. The onChange handler is called, updating the data
3. This triggers a re-render of the parent component (in this case, the entire table)
4. During the re-render, the dropdown is unmounted and remounted
5. This causes the dropdown to close before you can make multiple selections

The Solution: Deferred State Updates

The key insight is to separate local state management from parent state updates:

// Step 1: Add local state to track selections 
const [internalValue, setInternalValue] = useState<string[]>(value)

// Step 2: Handle popover open state changes
const handleOpenChange = useCallback((newOpen: boolean) => {
  if (open && !newOpen) {
    // Only update parent state when dropdown closes
    if (JSON.stringify(internalValue) !== JSON.stringify(value)) {
      onChange(internalValue);
    }
  }
  
  setOpen(newOpen);
  
  if (newOpen) {
    // Sync internal state with external state when opening
    setInternalValue(value);
  }
}, [open, internalValue, value, onChange]);

// Step 3: Toggle selection only updates internal state
const toggleSelection = useCallback((selectedValue: string) => {
  setInternalValue(prev => {
    if (prev.includes(selectedValue)) {
      return prev.filter(v => v !== selectedValue);
    } else {
      return [...prev, selectedValue];
    }
  });
}, []);

Why This Works

1. No parent re-renders during selection: Since we're only updating local state, the parent component doesn't re-render during selection.
2. Consistent UI: The dropdown shows accurate selected states using the internal value.
3. Data integrity: The final selections are properly synchronized back to the parent when done.
4. Resilient to external changes: Initial state is synchronized when opening the dropdown.

Implementation Steps

1. Create a local state variable to track selections inside the component
2. Only make selections against this local state while the dropdown is open
3. Defer updating the parent until the dropdown is explicitly closed
4. When opening, synchronize the internal state with the external value

Benefits

This pattern:

• Avoids re-render cycles that would unmount the dropdown
• Maintains UI consistency during multi-selection
• Simplifies the component's interaction with parent components
• Works with existing component lifecycles rather than fighting against them

This solution is much simpler than trying to prevent event propagation or manipulating DOM events, and addresses the root cause of the issue: premature re-rendering.