ShowHideLabel: Collapse button disappears when initialized expanded with short text

[unlikelyzero]

ShowHideLabel renders a Collapse button that disappears the moment you click it, when it's initialized already-expanded with text that doesn't actually need truncating.

Repro

<ShowHideLabel show={true} maxChars={256}>Short message</ShowHideLabel>

Text is shorter than maxChars, so no truncation is ever needed — but a Collapse button still renders, because needsButton is computed like this:

const [actualText, needsButton] = React.useMemo(() => {
  if (typeof children !== 'string') {
    return ['', false];
  }

  if (expanded) {
    return [children, true];
  }

  return [children.substr(0, maxChars), children.length > maxChars];
}, [children, expanded, maxChars]);

When expanded is true (from show={true}), needsButton is unconditionally true, regardless of whether the text is actually long enough to need a toggle. Clicking the rendered Collapse button flips expanded to false, which recomputes needsButton as children.length > maxChars — false for short text — so the button vanishes entirely rather than toggling back to an Expand button. The control disappears rather than behaving like a toggle.

Fix

needsButton should depend only on whether the text actually exceeds maxChars, independent of expanded:

const isLong = typeof children === 'string' && children.length > maxChars;
const actualText = expanded || !isLong ? children : children.slice(0, maxChars);
return [actualText, isLong];

Where I found this

Ran into this while reviewing #7267, which touches this same component's DOM structure for an aria-attribute fix but doesn't touch this logic.