Grouped changes to improve the overall readability and maintainability of the test.
A lot more can be done, but this is a good first step.
1) Use for-loops instead of duplicating lines to perform the same checks for each
node.
2) The {'txid': x, 'vout': y} dict is repeated everywhere in the test, both as
input to gettxspendingprevout and as part of its result when an output has no
known spender, making the test tedious to read and maintain.
This introduces a prevout(txid, vout) query helper and an unspent_out(txid, vout)
result helper to reduce the repetition. These two helpers are intentionally kept
separate to make it immediately clear whether a dict is an input to
gettxspendingprevout or an assertion on its result.
3) The same repetition problem mentioned above applies to other gettxspendingprevout
possible results:
Spent outputs returns {'txid': x, 'vout': y, 'spendingtxid': z} and
Spent outputs when requesting spending tx returns {'txid': x, 'vout': y,
'spendingtxid': z, 'blockhash': w, 'spendingtx': v}
To fix it, this introduces:
- spent_out(txid, vout, spending_tx_id): for outputs with a known spender
- spent_out_in_block(txid, vout, spending_tx_id, blockhash, spending_tx): for
outputs spent in a confirmed block, when full tx data is requested
4) Rename overloaded confirmed_utxo variable (used in three different tests) to more
descriptive names: root_utxo, reorg_replace_utxo, reorg_cancel_utxo to clarify
their roles in each of the tests.
We sync txospenderindex after we've checked the mempool for spending transaction, and only if search is not limited to the mempool and no
spending transactions have been found for some of the provided outpoints.
This should minimize the chance of having a block containing a spending transaction that is no longer in the mempool but has not been indexed yet.
Adds an outpoint -> txid index, which can be used to find which transactions spent a given output.
We use a composite key with 2 parts (suggested by @romanz): hash(spent outpoint) and tx position, with an empty value.
To find the spending tx for a given outpoint, we do a prefix search (prefix being the hash of the provided outpoint), and for all keys that match this prefix
we load the tx at the position specified in the key and return it, along with the block hash, if does spend the provided outpoint.
To handle reorgs we just erase the keys computed from the removed block.
This index is extremely useful for Lightning and more generally for layer-2 protocols that rely on chains of unpublished transactions.
If enabled, this index will be used by `gettxspendingprevout` when it does not find a spending transaction in the mempool.
