IndexedDB closure invoked recursively or after being dropped issue

[laruh]

Uncaught Error: closure invoked recursively or after being dropped

This runtime wasm error appears, when in storage implementations for wasm target we build cursor, open it, and iterate items in while loop, using next method of CursorIter

Could be connected to this

[laruh]

Some useful info:

Seems like the problem is that _onsuccess_closure and _onerror_closure closures are invoked after the CursorDriver has been dropped.

The thing is that CursorIter::collect() method uses next, but collect function usage after opening cursor doesnt have runtime errors, while items iteration with next has them.

Also here are functions which are needed to take into account:

• cursor_event_loop
• construct_event_closure

[borngraced]

this bug exist while calling next once like this(explained properly in my pr)

komodo-defi-framework/mm2src/coins/z_coin/storage/blockdb/blockdb_idb_storage.rs

Lines 90 to 98 in 272f46b

	let maybe_height = block_db
	.cursor_builder()
	.only("ticker", &ticker)?
	.bound("height", 0u32, u32::MAX)
	.reverse()
	.open_cursor(BlockDbTable::TICKER_HEIGHT_INDEX)
	.await?
	.next()
	.await?;

I have a fix here..that might close this issue too. can you test on your branch @laruh

[laruh]

@borngraced yeah, seems like the problem occurs when we try to get only first item with next() method. This fix solves runtime error :) Good job!

As you mentioned in PR description

return only the first result we care for and stop CursorDriver next loop immediately and Drop

I see that the problem was here

komodo-defi-framework/mm2src/mm2_db/src/indexed_db/drivers/cursor/cursor.rs

Lines 286 to 287 in 272f46b

	match cursor_action {
	CursorAction::Continue => cursor.continue_().map_to_mm(|e| CursorError::AdvanceError {

In the CursorDriver's next loop, the cursor_action was CursorAction::Continue type. However, due to the absence of the !first_row_only check, the continue_ method from web_sys was called, which attempted to invoke closures after CursorDriver being dropped.
In the get first item case CursorAction::Continue => cursor.continue_() wont be called, so no next items.