cmd/go: sort "no test files" test results into normal ordering

The code takes care to print test results during "go test ./..."
in the package order, delaying prints until it's that package's
turn, even when tests run in parallel. For some reason, the
prints about the test not running were not included in that,
making them print out of order. Fix that, printing that result
with the usual result printer.

This is particularly noticeable during all.bash when we start
letting cmd/dist vet packages without tests.

Change-Id: If07f9fe5a6fac2b57b24d599126b451357a164e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/630416
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>

src/cmd/go/internal/test/test.go

@@ -1387,6 +1387,27 @@ func (r *runTestActor) Act(b *work.Builder, ctx context.Context, a *work.Action)
 		return nil
 	}
 
+	// Stream test output (no buffering) when no package has
+	// been given on the command line (implicit current directory)
+	// or when benchmarking or fuzzing.
+	streamOutput := len(pkgArgs) == 0 || testBench != "" || testFuzz != ""
+
+	// If we're only running a single package under test or if parallelism is
+	// set to 1, and if we're displaying all output (testShowPass), we can
+	// hurry the output along, echoing it as soon as it comes in.
+	// We still have to copy to &buf for caching the result. This special
+	// case was introduced in Go 1.5 and is intentionally undocumented:
+	// the exact details of output buffering are up to the go command and
+	// subject to change. It would be nice to remove this special case
+	// entirely, but it is surely very helpful to see progress being made
+	// when tests are run on slow single-CPU ARM systems.
+	//
+	// If we're showing JSON output, then display output as soon as
+	// possible even when multiple tests are being run: the JSON output
+	// events are attributed to specific package tests, so interlacing them
+	// is OK.
+	streamAndCacheOutput := testShowPass() && (len(pkgs) == 1 || cfg.BuildP == 1) || testJSON
+
 	var stdout io.Writer = os.Stdout
 	var err error
 	var json *test2json.Converter
@@ -1399,6 +1420,17 @@ func (r *runTestActor) Act(b *work.Builder, ctx context.Context, a *work.Action)
 		stdout = json
 	}
 
+	var buf bytes.Buffer
+	if streamOutput {
+		// No change to stdout.
+	} else if streamAndCacheOutput {
+		// Write both to stdout and buf, for possible saving
+		// to cache, and for looking for the "no tests to run" message.
+		stdout = io.MultiWriter(stdout, &buf)
+	} else {
+		stdout = &buf
+	}
+
 	// Release next test to start (test2json.NewConverter writes the start event).
 	close(r.next)
 
@@ -1412,6 +1444,9 @@ func (r *runTestActor) Act(b *work.Builder, ctx context.Context, a *work.Action)
 		// Tell the JSON converter that this was a failure, not a passing run.
 		err = errors.New("build failed")
 		base.SetExitStatus(1)
+		if stdout == &buf {
+			a.TestOutput = &buf
+		}
 		return nil
 	}
 
@@ -1452,37 +1487,10 @@ func (r *runTestActor) Act(b *work.Builder, ctx context.Context, a *work.Action)
 		if reportNoTestFiles {
 			fmt.Fprintf(stdout, "?   \t%s\t[no test files]\n", p.ImportPath)
 		}
-		return nil
-	}
-
-	var buf bytes.Buffer
-	if len(pkgArgs) == 0 || testBench != "" || testFuzz != "" {
-		// Stream test output (no buffering) when no package has
-		// been given on the command line (implicit current directory)
-		// or when benchmarking or fuzzing.
-		// No change to stdout.
-	} else {
-		// If we're only running a single package under test or if parallelism is
-		// set to 1, and if we're displaying all output (testShowPass), we can
-		// hurry the output along, echoing it as soon as it comes in.
-		// We still have to copy to &buf for caching the result. This special
-		// case was introduced in Go 1.5 and is intentionally undocumented:
-		// the exact details of output buffering are up to the go command and
-		// subject to change. It would be nice to remove this special case
-		// entirely, but it is surely very helpful to see progress being made
-		// when tests are run on slow single-CPU ARM systems.
-		//
-		// If we're showing JSON output, then display output as soon as
-		// possible even when multiple tests are being run: the JSON output
-		// events are attributed to specific package tests, so interlacing them
-		// is OK.
-		if testShowPass() && (len(pkgs) == 1 || cfg.BuildP == 1) || testJSON {
-			// Write both to stdout and buf, for possible saving
-			// to cache, and for looking for the "no tests to run" message.
-			stdout = io.MultiWriter(stdout, &buf)
-		} else {
-			stdout = &buf
+		if stdout == &buf {
+			a.TestOutput = &buf
 		}
+		return nil
 	}
 
 	if r.c.buf == nil {
@@ -2082,8 +2090,13 @@ func builderCleanTest(b *work.Builder, ctx context.Context, a *work.Action) erro
 
 // builderPrintTest is the action for printing a test result.
 func builderPrintTest(b *work.Builder, ctx context.Context, a *work.Action) error {
-	clean := a.Deps[0]
-	run := clean.Deps[0]
+	run := a.Deps[0]
+	if run.Mode == "test clean" {
+		run = run.Deps[0]
+	}
+	if run.Mode != "test run" {
+		base.Fatalf("internal error: cannot find test run to print")
+	}
 	if run.TestOutput != nil {
 		os.Stdout.Write(run.TestOutput.Bytes())
 		run.TestOutput = nil

src/cmd/go/testdata/script/test_print.txt

@@ -0,0 +1,27 @@
+[short] skip
+
+go test ./...
+stdout 'pkg1(.|\n)*pkg2'
+
+-- go.mod --
+module m
+
+-- pkg1/x_test.go --
+package pkg1
+
+import (
+	"testing"
+	"time"
+)
+
+func Test(t *testing.T) {
+	// This sleep makes it more likely that pkg2 will be ready before pkg1,
+	// which previously would have made this test fail, because pkg2 would
+	// be printed before pkg1.
+	// Now that there is proper ordering, the Sleep should not matter.
+	// In particular, the Sleep does not make the test pass and won't
+	// be a problem on slow builders.
+	time.Sleep(1*time.Second)
+}
+-- pkg2/x.go --
+package pkg2