proposal: testing: support running subtests of different root tests using 'go test -run'

[dnephin]

The go test -run flag can be used to select multiple root test cases. This example will run the 3 tests which match the regex exactly:

go test -run '^(TestOne|TestTwo|TestThree)$'

As far as I can tell, the logic for handling subtests makes it impossible to do the same with subtest cases. It seems to be possible to run multiple root test cases, with a single subtest case:

go test -run '^TestOne$|^TestTwo$|^TestThree$/^SubTestA$'

But adding anything after the / is assumed to be a sub-sub test, and does not match the same way.

Some other things that I tried, which do not work:

Matches any SubTestA, not just the one from TestThree

^(TestOne|TestTwo|TestThree)$/^SubTestA$

Does not match any subtests

Because of how parenthesis are handled in splitRegex

(^TestOne$|^TestTwo$|^TestThree$/^SubTestA$)

Would it be reasonable to support this with the -run flag? Looking over the matching logic in src/testing it seems like this may not be a small change.

[ianlancetaylor]

CC @mpvl

[dnephin]

I see there was some discussion about this in https://go-review.googlesource.com/c/go/+/19122/. I think the | character is not accounted for (none of the tests include a case with one). I can't see any way to make this work splitting the regex by /.

Maybe the same goal can be accomplished by adding [^/]* before and after any non-anchored / in the regex? I guess that only solves part of it. I'm not sure how to have parent tests match the regex so that all subtests are evaluated.