blockchain: Combine ErrDoubleSpend & ErrMissingTx. #1064
Merged
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This replaces the
ErrDoubleSpend
andErrMissingTx
error codes with a single error code namedErrMissingTxOut
and updates the relevant errors and expected test results accordingly.Once upon a time, the code relied on a transaction index, so it was able to definitively differentiate between a transaction output that legitimately did not exist and one that had already been spent.
However, since the code now uses a pruned utxoset, it is no longer possible to reliably differentiate since once all outputs of a transaction are spent, it is removed from the utxoset completely. Consequently, a missing transaction could be either because the transaction never existed or because it is fully spent.
Also, while here, consistently use the
LookupEntry
function on theUtxoView
instead of directly accessing the internal map as intended.