cmd/dist: emphasize when all tests are excluded
As observed in https://go.dev/issue/61666#issuecomment-
1739476954,
if a -run flag value matches no tests, dist test output doesn't do much
to help users notice that was what happened. It is valid and sometimes
intended¹ to match no tests, so I want to reserve failed status with
exit code 1 to the actionable outcome where at least 1 test failed.
But it seems reasonable to extend the existing "some were excluded"
mechanism of reporting partial testing to be more helpful.
In non-JSON mode, which is more likely to be used manually by humans,
print a special² last line that will hopefully be easier to notice when
matching no tests wasn't intended. Change nothing for -json mode since
that's likely used by machines and they can make sense of 0 JSON events.
The go test command already has this behavior, so this brings dist test
closer³ to it. (Slightly unfortunate duplicate maintenance for us, and
the need for the rare dist test users to learn its CLI quirks; oh well.)
¹ It might seem counter-intuitive at first: what's the point of calling
dist test and asking it to run no tests? One possible answer is that
it permits writing code capable of running N intended tests, where N
is 0 or higher. That is, it allows for 0 to not be a special case that
the caller would have no choice but handle differently.
² I initially considered making it say something like "N of M tests were
excluded", but decided to leave it alone since the current coordinator
code still has that text hardcoded and I don't want to break it. Hence
the new status that I expect only humans will see. And it seems better
this way anyway.
³ In particular, the "matched no tests" and "no tests to run" phrases
were selected precisely because they're already used in cmd/go output.
Change-Id: I6768d9932587195ae6dbc6e2c4742479e265733b
Reviewed-on: https://go-review.googlesource.com/c/go/+/532115
Reviewed-by: Austin Clements <austin@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>