Add heuristics to stats.ino comparison when bigint is not available #694
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mbargiel
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Sorry about the last commit (10b96d3), I pushed too fast - it's unnecessary. I removed it. |
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Checked the coverage loss - it's due to the fact that the code branch where I added the heuristic checks was not covered by tests (of course, since BigInt is supported in the test runs used by the coverage check). |
manidlou
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Jul 26, 2019
lib/util/stat.js
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| throw new Error(errMsg(src, dest, funcName)) | ||
| } | ||
| return checkParentPathsSync(src, srcStat, destParent, funcName) | ||
| } | ||
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| function areApparentlyIdentical (srcStat, destStat) { |
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This is good but the function name is a bit confusing. Will you please rename it to something simpler like just areIdentical?
manidlou
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Jul 27, 2019
mbargiel
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I'm good with merging. |
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The resolution of #657 relies on Node >= 10.5, but actually leaves the issue not fixed on previous versions of Node (in particular, for the OP, who reported the issue on Node 8.11.3). The issue particularly problematic and frequent in automated setups, such as running tests that create files in sequence, where it is likely to happen.
This PR minimizes the frequency of this issue by comparing additional
fs.Statsvalues whenBigintsupport is not available. Note that the check is still heuristic: different stats prove they are different files*, but while same stats do not prove they are the same, we must err on the side of caution and still treat them as the same file.(*) Race condition: comparing file stats before performing a copy or other operation implicitly introduces a race condition. However the existing implementation already suffered from this, so we presume that this PR does not make the condition much worse (with the exception that unlike
inoandvol, a malicious user could in theory manipulate some of the otherstats). In practice, this race condition seems extremely hard to abuse, since it requires using a vulnerable system, and a means to change the file stats between the twostatscalls made bygetStatsandgetStatsSync.