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Fix unsafe type assertions in nestLists using discriminated union narrowing #141

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Fix unsafe type assertions in nestLists using discriminated union narrowing #141

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Copilot Dec 9, 2025
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Fix unsafe type assertions in nestLists.ts
Copilot Dec 9, 2025
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15 changes: 7 additions & 8 deletions src/nestLists.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -89,17 +89,18 @@ export function nestLists<T extends TypedObject = PortableTextBlock | TypedObjec
if ((block.level || 1) > currentList.level) {
const newList = listFromBlock(block, i, mode)

if (mode === 'html') {
if (currentList.mode === 'html' && newList.mode === 'html') {
// Because HTML is kinda weird, nested lists needs to be nested within list items.
// So while you would think that we could populate the parent list with a new sub-list,
// we actually have to target the last list element (child) of the parent.
// However, at this point we need to be very careful - simply pushing to the list of children
// will mutate the input, and we don't want to blindly clone the entire tree.

// Clone the last child while adding our new list as the last child of it
const lastListItem = currentList.children[
currentList.children.length - 1
] as ToolkitPortableTextListItem
const lastListItem = currentList.children[currentList.children.length - 1]
if (!lastListItem) {
continue
}

const newLastChild: ToolkitPortableTextListItem = {
...lastListItem,
Expand All @@ -108,10 +109,8 @@ export function nestLists<T extends TypedObject = PortableTextBlock | TypedObjec

// Swap the last child
currentList.children[currentList.children.length - 1] = newLastChild
} else {
;(currentList as ToolkitPortableTextDirectList).children.push(
newList as ToolkitPortableTextDirectList,
)
} else if (currentList.mode === 'direct' && newList.mode === 'direct') {
currentList.children.push(newList)
}

// Set the newly created, deeper list as the current
Expand Down