code review 150980043: cmd/go: always build _test.go files and link into test

cmd/go: always build _test.go files and link into test

go test's handling of _test.go files when the entire
package's set of files has no Test functions has varied
over the past few releases. There are a few interesting
cases (all contain no Test functions):
        (1) x_test.go has syntax errors
        (2) x_test.go has type errors
        (3) x_test.go has runtime errors (say, a func init that panics)

In Go 1.1, tests with (1) or (2) failed; (3) passed.
In Go 1.2, tests with (1) or (2) failed; (3) passed.
In Go 1.3, tests with (1) failed; (2) or (3) passed.
After this CL, tests with (1), (2), or (3) all fail.

This is clearly a corner case, but it seems to me that
the behavior of the test should not change if you
add or remove a line like

        func TestAlwaysPasses(t *testing.T) {}

That implies that the _test.go files must always
be built and always be imported into the test binary.
Doing so means that (1), (2), and (3) must all fail.

Fixes issue 8337.

[rsc, 2014-09-26 19:31:13]

Hello golang-codereviews@googlegroups.com (cc: adg, iant, r),

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

[iant, 2014-09-26 20:20:20]

LGTM

Needs to be mentioned in go1.4.txt.

[rsc, 2014-09-26 21:09:16]

*** Submitted as https://code.google.com/p/go/source/detail?r=c47d4e23f986 ***

cmd/go: always build _test.go files and link into test

go test's handling of _test.go files when the entire
package's set of files has no Test functions has varied
over the past few releases. There are a few interesting
cases (all contain no Test functions):
        (1) x_test.go has syntax errors
        (2) x_test.go has type errors
        (3) x_test.go has runtime errors (say, a func init that panics)

In Go 1.1, tests with (1) or (2) failed; (3) passed.
In Go 1.2, tests with (1) or (2) failed; (3) passed.
In Go 1.3, tests with (1) failed; (2) or (3) passed.
After this CL, tests with (1), (2), or (3) all fail.

This is clearly a corner case, but it seems to me that
the behavior of the test should not change if you
add or remove a line like

        func TestAlwaysPasses(t *testing.T) {}

That implies that the _test.go files must always
be built and always be imported into the test binary.
Doing so means that (1), (2), and (3) must all fail.

Fixes issue 8337.

LGTM=iant
R=golang-codereviews, iant
CC=adg, golang-codereviews, r
https://codereview.appspot.com/150980043