cmd/go: test mixes stderr and stdout #25241
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agnivade
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agnivade
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NeedsInvestigation
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This is horrible and next to unusable. Users should be able to opt-in to getting this output, not forced in. |
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I'm sorry your benchmarks print so much to standard error. I'm sorry we didn't get to it in Go 1.11. |
bcmills
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#24929 may also affect this behavior. |
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I have just come across this issue, when trying to redirect stderr independently from stdout from a test only to discover this isn't possible. A quick investigation identified that this is happening in parent process for the test during go/src/cmd/go/internal/test/test.go Line 1636 in 81c66e7 It's not clear to me why stderr can't be handled separately, I suspect there might be something that requires the combined output? |
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We've had this behavior for a while, and now I wonder if there are some users who are expecting it and would be surprised if we separated them out. |
This reasoning can be used to justify status quo anywhere that undocumented behavior exists. 🤷 |
That's fair. I would like to hear from users who would like to see this change to see if there's enough demand to try and see if we can change the output behavior. My guess is that the change was originally made to make the test outputs easier to cache. There's just one cached output file currently rather a stdout output and a stderr output, or a stdout section and stderr section in a single file |
The mixing of stdout/stderr seems a bit wrong from a Unix philosophy perspective. But I no longer work on CockroachDB (or really write Go at all), so it doesn't especially bother me any longer. I imagine @andreimatei is in a similar boat. |
7badae8 appears to have made
go testmix stderr and stdout from tests, which has made go 1.10 a regression for CockroachDB's benchmarks.This issue is related to #18010 :
Not only is the benchmark output not swallowed, but stderr and stdout are now mixed, so, if our binary produces logs (on stderr, as ours does), it's now impossible to see the benchmark results or use tools like
benchstat.In particular, I believe
benchstatfails to work because the mixing of stderr and stdout doesn't even use line buffering - so the benchmark measurements lines are mixed with log lines andbenchstatcan't recognize them any more.I generally concur with the folks on #18010 arguing that the swallowing/not swallowing of output is inconsistent (and there's no control over it as far as I can tell). Additionally, now the mixing of stdout and stderr is really a problem. The argument for not doing anything about
go test -benchnot swallowing output was that "we should at least preserve existing behavior as much as possible", but it would appear that existing behavior was changed in a quite significant way by this mixing. So I would kindly ask for the swallowing decision to be re-evaluated.What version of Go are you using (
go version)?go version go1.10 darwin/amd64
Does this issue reproduce with the latest release?
Yes
What operating system and processor architecture are you using (
go env)?OS X/ amd64
cc @benesch
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