Writing to stdout without a newline causes `go_test` output errors

[bryceitoc9]

What version of rules_go are you using?

v.0.39.1

What version of gazelle are you using?

v.0.30.0

What version of Bazel are you using?

5.4.0

Does this issue reproduce with the latest releases of all the above?

Unsure re: Bazel version, yes re: rules/Gazelle

What operating system and processor architecture are you using?

MacOS v13.3.1, m1

Any other potentially useful information about your toolchain?

N/A

What did you do?

Function tested with a go_test test outputs text to stdout via fmt.Printf without a newline. In the below example, Invalid data found for filename: path/to/test/file.go, skipping is outputted via fmt.Printf.

This was discovered while troubleshooting a flaky test: this was a parallel execution, and we were able to replicate with 100% accuracy by adding a fmt.Print statement to the test function itself.

What did you expect to see?

Tests successfully passing, with a clean test.xml output file.

What did you see instead?

test.log seems fine, but test.xml outputs errors. Test execution exits with a status code of 0.

test.log:

exec ${PAGER:-/usr/bin/less} "$0" || exit 1
Executing tests from //path/to/project:go_default_test
-----------------------------------------------------------------------------
=== RUN   TestOutputMetrics
=== PAUSE TestOutputMetrics
=== CONT  TestOutputMetrics
=== RUN   TestOutputMetrics/Successful_Test
=== PAUSE TestOutputMetrics/Successful_Test
=== RUN   TestOutputMetrics/Missing_Name
=== PAUSE TestOutputMetrics/Missing_Name
=== RUN   TestOutputMetrics/Missing_IntVal
=== PAUSE TestOutputMetrics/Missing_IntVal
=== RUN   TestOutputMetrics/Bad_Int_Val
=== PAUSE TestOutputMetrics/Bad_Int_Val
=== CONT  TestOutputMetrics/Successful_Test
=== CONT  TestOutputMetrics/Missing_Name
=== CONT  TestOutputMetrics/Missing_IntVal
=== CONT  TestOutputMetrics/Bad_Int_Val
Invalid data found for filename: path/to/test/file.go, skipping--- PASS: TestOutputMetrics (0.00s)
    --- PASS: TestOutputMetrics/Successful_Test (0.00s)
    --- PASS: TestOutputMetrics/Missing_Name (0.00s)
    --- PASS: TestOutputMetrics/Bad_Int_Val (0.00s)
    --- PASS: TestOutputMetrics/Missing_IntVal (0.00s)
PASS

test.xml:

<testsuites>
	<testsuite errors="5" failures="0" skipped="0" tests="5" time="0.005" name="github.com/org/repo/path/to/project">
		<testcase classname="project" name="TestOutputMetrics" time="">
			<error message="No pass/skip/fail event found for test" type="">=== RUN   TestOutputMetrics&#xA;=== PAUSE TestOutputMetrics&#xA;=== CONT  TestOutputMetrics&#xA;</error>
		</testcase>
		<testcase classname="project" name="TestOutputMetrics/Bad_Int_Val" time="">
			<error message="No pass/skip/fail event found for test" type="">=== RUN   TestOutputMetrics/Bad_Int_Val&#xA;=== PAUSE TestOutputMetrics/Bad_Int_Val&#xA;=== CONT  TestOutputMetrics/Bad_Int_Val&#xA;Invalid data found for filename: path/to/test/file.go, skipping--- PASS: TestOutputMetrics (0.00s)&#xA;    --- PASS: TestOutputMetrics/Successful_Test (0.00s)&#xA;    --- PASS: TestOutputMetrics/Missing_Name (0.00s)&#xA;    --- PASS: TestOutputMetrics/Bad_Int_Val (0.00s)&#xA;    --- PASS: TestOutputMetrics/Missing_IntVal (0.00s)&#xA;</error>
		</testcase>
		<testcase classname="project" name="TestOutputMetrics/Missing_IntVal" time="">
			<error message="No pass/skip/fail event found for test" type="">=== RUN   TestOutputMetrics/Missing_IntVal&#xA;=== PAUSE TestOutputMetrics/Missing_IntVal&#xA;=== CONT  TestOutputMetrics/Missing_IntVal&#xA;</error>
		</testcase>
		<testcase classname="project" name="TestOutputMetrics/Missing_Name" time="">
			<error message="No pass/skip/fail event found for test" type="">=== RUN   TestOutputMetrics/Missing_Name&#xA;=== PAUSE TestOutputMetrics/Missing_Name&#xA;=== CONT  TestOutputMetrics/Missing_Name&#xA;</error>
		</testcase>
		<testcase classname="project" name="TestOutputMetrics/Successful_Test" time="">
			<error message="No pass/skip/fail event found for test" type="">=== RUN   TestOutputMetrics/Successful_Test&#xA;=== PAUSE TestOutputMetrics/Successful_Test&#xA;=== CONT  TestOutputMetrics/Successful_Test&#xA;</error>
		</testcase>
	</testsuite>
</testsuites>

[fmeum]

This may be fixed by updating our copy of test2json.go to https://github.com/golang/go/commit/1c72ee7f13831b215b8744f6b35bc4fd53aba5e2#diff-aba3251fae880161e12c38219025123ca9af7607a42f87c7234cb201c770fa04, which was made in response to https://github.com/golang/go/issues/26325.

@bryceitoc9 Would you be interested in turning that into a PR? I could support you along the way.

[tingilee]

We also ran into this issue, created https://github.com/bazelbuild/rules_go/pull/3662 to hopefully address it as suggested.

[tingilee]

I just patched this in our repo and noticed that it didn't solve the parsing issue into test.xml. This issue will need to be reopened.