cmd/cover: should support -coverprofile unifying tests from multiple packages

[wadey]

What steps will reproduce the problem?
If possible, include a link to a program on play.golang.org.
1. run `go test -coverprofile=coverage.out ./...`

What is the expected output?

coverage.out contains coverage all of the specified packages

What do you see instead?

`cannot use test profile flag with multiple packages`

Which compiler are you using (5g, 6g, 8g, gccgo)?

6g

Which operating system are you using?

OS X 10.9

Which version are you using?  (run 'go version')

go version go1.2 darwin/amd64

Please provide any additional information below.

If I manually construct a coverage.out file from multiple packages, it seems to work
fine:

1. go test -coverprofile a.part ./a
2. go test -coverprofile b.part ./b
3. echo "mode: set" >coverage.out
4. grep -h -v "mode: set" *.part >>coverage.out
5. go tool cover -html=coverage.out

Why can't `go test -coverprofile` do this automatically?

[minux]

Comment 1:

Labels changed: added release-go1.3maybe, repo-tools.

Status changed to Accepted.

[rsc]

Comment 3:

Labels changed: added release-none, removed release-go1.3maybe.

Comment 4:

With the 1.3 release, any idea when this will be fixed?

[gopherbot]

Comment 5 by phuna24:

I'm also facing same problem today with 1.3.1. Is there plan for fixing this soon?

[gopherbot]

Comment 6 by hwang.dev:

It is not an urgent issue. The workaround is simple, please check the shell script:
https://gist.github.com/hailiang/0f22736320abe6be71ce

[gopherbot]

Comment 7 by phuna24:

Hi,
Thanks for the link. Very helpful.

[gopherbot]

Comment 8:

CL https://golang.org/cl/159910044 mentions this issue.

[dlsniper]

Can this be included in 1.5. I don't see any technical reason for it to not be. Thank you.

[minux]

As long as someone wants to work on this issue to solve it properly..... The mentioned CL is not the way to go (overwriting the cover profiles instead of combining them).