File output flag for writing built images to a specified file

[marlon-gamez]

This is essentially the same as running skaffold build --quiet > file.out, but doesn't silence the standard output from skaffold.

[codecov]

Codecov Report

Merging #2476 into master will increase coverage by 0.03%.
The diff coverage is 60%.

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/build.go	79.41% <60%> (-9.05%)	⬇️
pkg/skaffold/docker/client.go	71.56% <0%> (+1.96%)	⬆️
pkg/skaffold/jib/jib.go	78.49% <0%> (+2.15%)	⬆️

[tejal29]

This looks good! Few comments

• if you have a --file-output flag on, the build output log lines should go to stdout. Is that happening? ( write tests to confirm that)
• Write tests where
  -- both --quiet and --file-output is present. In this case, either you shd see build output on std out and also in the file or error out saying both are not supported. I feel 1st is better.
  -- both --file-output and -o are present the file has the correct formatted output.
  • also make sure, if the builder prints some output it is written to std out when --file-output is present and no --quiet.

[tejal29]

Can you use ioutil.WriteFile like skaffold fix uses
here https://github.com/GoogleContainerTools/skaffold/blob/master/cmd/skaffold/app/cmd/fix.go#L73
if err := ioutil.WriteFile(configFile, newCfg, 0644); err != nil { }

[tejal29]

ah ok.
Can you create a bytes.buffer and execute the template there

buildOut bytes.Buffer
t.Execute(buildOut, r)

And the if --quiet is present,

out.Write(buildOut)

if "--file-output" is present,

err := ioutil.WriteFile(buildOutputFlag, buildOut, 0644)
if err != nil {
  log.Fatal(err)
}

That ways its cleaner and we do not overwrite out

[priyawadhwa]

looks good to me! could you add a unit test, maybe to TestQuietFlag or write a new one?

[priyawadhwa]

LGTM!

[tejal29]

yay!

[AndiDog]

Do we still need "Used in conjunction with --quiet flag" for -o, --output? I guess from now on that flag even applies without quiet mode?!

[marlon-gamez]

I think that should still be there, but be updated to say "Used in conjunction with --quiet or --file-output", since those are the only two flags whose output it effects.

[timowuttke]

Is there something off with the documentation? It works fine with skaffold build --file-output=blub but the documentation (and skaffold build --help) claims it should be skaffold build --output=blub which doesn't work.

[marlon-gamez]

Is there something off with the documentation? It works fine with skaffold build --file-output=blub but the documentation (and skaffold build --help) claims it should be skaffold build --output=blub which doesn't work.

--output is actually the flag used to format the output of --quiet (and now --file-output as well). The naming is a bit confusing, sorry about that. Running skaffold build --help should show documentation for both --output and --file-output.