add a check that same file is not copied twice #3712
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arcanis
reviewed
Jun 26, 2017
| @@ -163,6 +163,7 @@ async function buildActionsForCopy( | |||
| const {src, dest, type} = data; | |||
| const onFresh = data.onFresh || noop; | |||
| const onDone = data.onDone || noop; | |||
| invariant(!files.has(dest), `The same file ${dest} can't be copied twice in one bulk copy`); | |||
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Is it efficient? It O(N²), right?
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Why would it be?
Set should be implemented by a HashSet and its has operation should be sublinear, O(1) in an ideal situation.
https://jsperf.com/array-indexof-vs-set-has
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Yeah I'm wrong, I thought it was an array (in which case it would be iterating over the array for each element to copy, hence square complexity), but with a set it's all fine 👍
arcanis
approved these changes
Jun 26, 2017
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Summary
If the same file is copied twice during a bulk copy then we have a problem in out recursive logic.
Added an invariant to make sure we don't make extra IO operation.
Test plan
all tests pass