cmd/test2json: do not emit a final Action if the result is not known

If we are parsing a test output, and the test does not end in the
usual PASS or FAIL line (say, because it panicked), then we need the
exit status of the test binary in order to determine whether the test
passed or failed. If we don't have that status available, we shouldn't
guess arbitrarily — instead, we should omit the final "pass" or "fail"
action entirely.

(In practice, we nearly always DO have the final status, such as when
running 'go test' or 'go tool test2json some.exe'.)

Fixes golang#40132

Change-Id: Iae482577361a6033395fe4a05d746b980e18c3de
Reviewed-on: https://go-review.googlesource.com/c/go/+/248624
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

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

@@ -1098,9 +1098,13 @@ func (c *runCache) builderRunTest(b *work.Builder, ctx context.Context, a *work.
 	}
 
 	var stdout io.Writer = os.Stdout
+	var err error
 	if testJSON {
 		json := test2json.NewConverter(lockedStdout{}, a.Package.ImportPath, test2json.Timestamp)
-		defer json.Close()
+		defer func() {
+			json.Exited(err)
+			json.Close()
+		}()
 		stdout = json
 	}
 
@@ -1204,7 +1208,7 @@ func (c *runCache) builderRunTest(b *work.Builder, ctx context.Context, a *work.
 	}
 
 	t0 := time.Now()
-	err := cmd.Start()
+	err = cmd.Start()
 
 	// This is a last-ditch deadline to detect and
 	// stop wedged test binaries, to keep the builders

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

@@ -0,0 +1,102 @@
+[short] skip
+
+go test -c -o mainpanic.exe ./mainpanic &
+go test -c -o mainexit0.exe ./mainexit0 &
+go test -c -o testpanic.exe ./testpanic &
+go test -c -o testbgpanic.exe ./testbgpanic &
+wait
+
+# Test binaries that panic in TestMain should be marked as failing.
+
+! go test -json ./mainpanic
+stdout '"Action":"fail"'
+! stdout '"Action":"pass"'
+
+! go tool test2json ./mainpanic.exe
+stdout '"Action":"fail"'
+! stdout '"Action":"pass"'
+
+# Test binaries that exit with status 0 should be marked as passing.
+
+go test -json ./mainexit0
+stdout '"Action":"pass"'
+! stdout '"Action":"fail"'
+
+go tool test2json ./mainexit0.exe
+stdout '"Action":"pass"'
+! stdout '"Action":"fail"'
+
+# Test functions that panic should never be marked as passing
+# (https://golang.org/issue/40132).
+
+! go test -json ./testpanic
+stdout '"Action":"fail"'
+! stdout '"Action":"pass"'
+
+! go tool test2json ./testpanic.exe -test.v
+stdout '"Action":"fail"'
+! stdout '"Action":"pass"'
+
+! go tool test2json ./testpanic.exe
+stdout '"Action":"fail"'
+! stdout '"Action":"pass"'
+
+# Tests that panic in a background goroutine should be marked as failing.
+
+! go test -json ./testbgpanic
+stdout '"Action":"fail"'
+! stdout '"Action":"pass"'
+
+! go tool test2json ./testbgpanic.exe -test.v
+stdout '"Action":"fail"'
+! stdout '"Action":"pass"'
+
+! go tool test2json ./testbgpanic.exe
+stdout '"Action":"fail"'
+! stdout '"Action":"pass"'
+
+-- go.mod --
+module m
+go 1.14
+-- mainpanic/mainpanic_test.go --
+package mainpanic_test
+
+import "testing"
+
+func TestMain(m *testing.M) {
+	panic("haha no")
+}
+-- mainexit0/mainexit0_test.go --
+package mainexit0_test
+
+import (
+	"fmt"
+	"os"
+	"testing"
+)
+
+func TestMain(m *testing.M) {
+	fmt.Println("nothing to do")
+	os.Exit(0)
+}
+-- testpanic/testpanic_test.go --
+package testpanic_test
+
+import "testing"
+
+func TestPanic(*testing.T) {
+	panic("haha no")
+}
+-- testbgpanic/testbgpanic_test.go --
+package testbgpanic_test
+
+import "testing"
+
+func TestPanicInBackground(*testing.T) {
+	c := make(chan struct{})
+	go func() {
+		panic("haha no")
+		close(c)
+	}()
+	<-c
+}

src/cmd/internal/test2json/test2json.go

@@ -45,10 +45,10 @@ type textBytes []byte
 
 func (b textBytes) MarshalText() ([]byte, error) { return b, nil }
 
-// A converter holds the state of a test-to-JSON conversion.
+// A Converter holds the state of a test-to-JSON conversion.
 // It implements io.WriteCloser; the caller writes test output in,
 // and the converter writes JSON output to w.
-type converter struct {
+type Converter struct {
 	w        io.Writer  // JSON output stream
 	pkg      string     // package to name in events
 	mode     Mode       // mode bits
@@ -100,9 +100,9 @@ var (
 //
 // The pkg string, if present, specifies the import path to
 // report in the JSON stream.
-func NewConverter(w io.Writer, pkg string, mode Mode) io.WriteCloser {
-	c := new(converter)
-	*c = converter{
+func NewConverter(w io.Writer, pkg string, mode Mode) *Converter {
+	c := new(Converter)
+	*c = Converter{
 		w:     w,
 		pkg:   pkg,
 		mode:  mode,
@@ -122,11 +122,20 @@ func NewConverter(w io.Writer, pkg string, mode Mode) io.WriteCloser {
 }
 
 // Write writes the test input to the converter.
-func (c *converter) Write(b []byte) (int, error) {
+func (c *Converter) Write(b []byte) (int, error) {
 	c.input.write(b)
 	return len(b), nil
 }
 
+// Exited marks the test process as having exited with the given error.
+func (c *Converter) Exited(err error) {
+	if err == nil {
+		c.result = "pass"
+	} else {
+		c.result = "fail"
+	}
+}
+
 var (
 	// printed by test on successful run.
 	bigPass = []byte("PASS\n")
@@ -160,7 +169,7 @@ var (
 // handleInputLine handles a single whole test output line.
 // It must write the line to c.output but may choose to do so
 // before or after emitting other events.
-func (c *converter) handleInputLine(line []byte) {
+func (c *Converter) handleInputLine(line []byte) {
 	// Final PASS or FAIL.
 	if bytes.Equal(line, bigPass) || bytes.Equal(line, bigFail) || bytes.HasPrefix(line, bigFailErrorPrefix) {
 		c.flushReport(0)
@@ -286,7 +295,7 @@ func (c *converter) handleInputLine(line []byte) {
 }
 
 // flushReport flushes all pending PASS/FAIL reports at levels >= depth.
-func (c *converter) flushReport(depth int) {
+func (c *Converter) flushReport(depth int) {
 	c.testName = ""
 	for len(c.report) > depth {
 		e := c.report[len(c.report)-1]
@@ -298,23 +307,22 @@ func (c *converter) flushReport(depth int) {
 // Close marks the end of the go test output.
 // It flushes any pending input and then output (only partial lines at this point)
 // and then emits the final overall package-level pass/fail event.
-func (c *converter) Close() error {
+func (c *Converter) Close() error {
 	c.input.flush()
 	c.output.flush()
-	e := &event{Action: "pass"}
 	if c.result != "" {
-		e.Action = c.result
-	}
-	if c.mode&Timestamp != 0 {
-		dt := time.Since(c.start).Round(1 * time.Millisecond).Seconds()
-		e.Elapsed = &dt
+		e := &event{Action: c.result}
+		if c.mode&Timestamp != 0 {
+			dt := time.Since(c.start).Round(1 * time.Millisecond).Seconds()
+			e.Elapsed = &dt
+		}
+		c.writeEvent(e)
 	}
-	c.writeEvent(e)
 	return nil
 }
 
 // writeOutputEvent writes a single output event with the given bytes.
-func (c *converter) writeOutputEvent(out []byte) {
+func (c *Converter) writeOutputEvent(out []byte) {
 	c.writeEvent(&event{
 		Action: "output",
 		Output: (*textBytes)(&out),
@@ -323,7 +331,7 @@ func (c *converter) writeOutputEvent(out []byte) {
 
 // writeEvent writes a single event.
 // It adds the package, time (if requested), and test name (if needed).
-func (c *converter) writeEvent(e *event) {
+func (c *Converter) writeEvent(e *event) {
 	e.Package = c.pkg
 	if c.mode&Timestamp != 0 {
 		t := time.Now()

src/cmd/internal/test2json/testdata/benchshort.json

@@ -4,4 +4,3 @@
 {"Action":"output","Output":"# but to avoid questions of timing, we just use a file with no \\n at all.\n"}
 {"Action":"output","Output":"BenchmarkFoo   \t"}
 {"Action":"output","Output":"10000 early EOF"}
-{"Action":"pass"}

src/cmd/internal/test2json/testdata/empty.json

@@ -1 +0,0 @@
-{"Action":"pass"}

src/cmd/test2json/main.go

@@ -118,12 +118,16 @@ func main() {
 		w := &countWriter{0, c}
 		cmd.Stdout = w
 		cmd.Stderr = w
-		if err := cmd.Run(); err != nil {
+		err := cmd.Run()
+		if err != nil {
 			if w.n > 0 {
 				// Assume command printed why it failed.
 			} else {
 				fmt.Fprintf(c, "test2json: %v\n", err)
 			}
+		}
+		c.Exited(err)
+		if err != nil {
 			c.Close()
 			os.Exit(1)
 		}