code review 10264045: cmd/go: write coverage to file, add percentage statistic

cmd/go: write coverage to file, add percentage statistic
Move the data dumper to the testing package, where it has access
to file I/O.
Print a percentage value at the end of the run.

[r, 2013-06-13 21:08:19]

Hello rsc (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go

[adg, 2013-06-18 03:46:07]

https://codereview.appspot.com/10264045/diff/15001/src/pkg/testing/cover.go
File src/pkg/testing/cover.go (right):

https://codereview.appspot.com/10264045/diff/15001/src/pkg/testing/cover.go#n...
src/pkg/testing/cover.go:48: defer f.Close()
should check the error return value of f.Close when writing

https://codereview.appspot.com/10264045/diff/15001/src/pkg/testing/cover.go#n...
src/pkg/testing/cover.go:76: panic(err)
panic? why not print "testing: err" and os.Exit(2) as with the Create above?

[r, 2013-06-18 16:05:20]

Hello rsc@golang.org, adg@golang.org (cc: golang-dev@googlegroups.com),

Please take another look.

[r, 2013-06-18 20:57:35]

Hello rsc@golang.org, adg@golang.org (cc: golang-dev@googlegroups.com),

Please take another look.

[rsc, 2013-06-18 21:05:08]

LGTM

https://codereview.appspot.com/10264045/diff/28001/src/cmd/go/test.go
File src/cmd/go/test.go (right):

https://codereview.appspot.com/10264045/diff/28001/src/cmd/go/test.go#newcode...
src/cmd/go/test.go:1012: testing.CoverRegister(coverCounters, coverBlocks)
s/CoverRegister/RegisterCover/
to match various other registrations in the standard library.

https://codereview.appspot.com/10264045/diff/31001/src/cmd/go/test.go
File src/cmd/go/test.go (right):

https://codereview.appspot.com/10264045/diff/31001/src/cmd/go/test.go#newcode127
src/cmd/go/test.go:127: -cover set,count,atomic
Not for this CL, but ...

I think this should probably be covermode, which like coverprofile would be a
parameter that can be omitted.
The -cover flag should be a boolean that enables coverage at all, using the
covermode and coverprofile settings.

Then 

go test -cover regexp

does something useful.

https://codereview.appspot.com/10264045/diff/31001/src/cmd/go/test.go#newcode136
src/cmd/go/test.go:136: Sets -v.
TODO: This will change.

https://codereview.appspot.com/10264045/diff/31001/src/cmd/go/testflag.go
File src/cmd/go/testflag.go (right):

https://codereview.appspot.com/10264045/diff/31001/src/cmd/go/testflag.go#new...
src/cmd/go/testflag.go:188: // Guarantee we see the coverage statistics. Doesn't
turn -v on generally; tricky. TODO?
Fine for now.

I suspect that the thing to do is to parse the (collected but suppressed) output
to find the coverage information and show it in the table. Where go test std
currently says:

ok  	compress/bzip2	0.086s
ok  	compress/flate	0.957s
ok  	compress/gzip	0.029s
ok  	compress/lzw	0.136s
ok  	compress/zlib	1.411s
ok  	container/heap	0.025s

'go test -cover std' might say:

ok  	compress/bzip2	0.086s  93% coverage
ok  	compress/flate	0.957s  95% coverage
ok  	compress/gzip	0.029s  80% coverage
ok  	compress/lzw	0.136s  20% coverage
ok  	compress/zlib	1.411s  45% coverage
ok  	container/heap	0.025s  100% coverage

[r, 2013-06-18 21:18:29]

*** Submitted as https://code.google.com/p/go/source/detail?r=8e10088eb699 ***

cmd/go: write coverage to file, add percentage statistic
Move the data dumper to the testing package, where it has access
to file I/O.
Print a percentage value at the end of the run.

R=rsc, adg
CC=golang-dev
https://codereview.appspot.com/10264045

https://codereview.appspot.com/10264045/diff/15001/src/pkg/testing/cover.go
File src/pkg/testing/cover.go (right):

https://codereview.appspot.com/10264045/diff/15001/src/pkg/testing/cover.go#n...
src/pkg/testing/cover.go:48: defer f.Close()
On 2013/06/18 03:46:07, adg wrote:
> should check the error return value of f.Close when writing

meh. and do what? stupid idea, but the orthodoxy.

https://codereview.appspot.com/10264045/diff/15001/src/pkg/testing/cover.go#n...
src/pkg/testing/cover.go:76: panic(err)
On 2013/06/18 03:46:07, adg wrote:
> panic? why not print "testing: err" and os.Exit(2) as with the Create above?

Done.