Revert "testing: add Output"

This reverts commit 8d189f188e225e4919b34c0c097e75dfda255949.

Reason for revert: failing test

Change-Id: I951087eaef7818697acf87e3206003bcc8a81ee2
Reviewed-on: https://go-review.googlesource.com/c/go/+/672335
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

1 files changed, 64 insertions, 150 deletions

diff --git a/src/testing/testing.go b/src/testing/testing.go
index efbcd59dc0..d50abea32f 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -631,7 +631,6 @@ type common struct {
 	mu          sync.RWMutex         // guards this group of fields
 	output      []byte               // Output generated by test or benchmark.
 	w           io.Writer            // For flushToParent.
-	o           *outputWriter        // Writes output.
 	ran         bool                 // Test or benchmark (or one of its subtests) was executed.
 	failed      bool                 // Test or benchmark has failed.
 	skipped     bool                 // Test or benchmark has been skipped.
@@ -800,6 +799,44 @@ func (c *common) frameSkip(skip int) runtime.Frame {
 	return firstFrame
 }
 
+// decorate prefixes the string with the file and line of the call site
+// and inserts the final newline if needed and indentation spaces for formatting.
+// This function must be called with c.mu held.
+func (c *common) decorate(s string, skip int) string {
+	frame := c.frameSkip(skip)
+	file := frame.File
+	line := frame.Line
+	if file != "" {
+		if *fullPath {
+			// If relative path, truncate file name at last file name separator.
+		} else if index := strings.LastIndexAny(file, `/\`); index >= 0 {
+			file = file[index+1:]
+		}
+	} else {
+		file = "???"
+	}
+	if line == 0 {
+		line = 1
+	}
+	buf := new(strings.Builder)
+	// Every line is indented at least 4 spaces.
+	buf.WriteString("    ")
+	fmt.Fprintf(buf, "%s:%d: ", file, line)
+	lines := strings.Split(s, "\n")
+	if l := len(lines); l > 1 && lines[l-1] == "" {
+		lines = lines[:l-1]
+	}
+	for i, line := range lines {
+		if i > 0 {
+			// Second and subsequent lines are indented an additional 4 spaces.
+			buf.WriteString("\n        ")
+		}
+		buf.WriteString(line)
+	}
+	buf.WriteByte('\n')
+	return buf.String()
+}
+
 // flushToParent writes c.output to the parent after first writing the header
 // with the given format and arguments.
 func (c *common) flushToParent(testName, format string, args ...any) {
@@ -845,8 +882,6 @@ type indenter struct {
 	c *common
 }
 
-const indent = "    "
-
 func (w indenter) Write(b []byte) (n int, err error) {
 	n = len(b)
 	for len(b) > 0 {
@@ -863,6 +898,7 @@ func (w indenter) Write(b []byte) (n int, err error) {
 			w.c.output = append(w.c.output, marker)
 			line = line[1:]
 		}
+		const indent = "    "
 		w.c.output = append(w.c.output, indent...)
 		w.c.output = append(w.c.output, line...)
 		b = b[end:]
@@ -1007,156 +1043,41 @@ func (c *common) FailNow() {
 	runtime.Goexit()
 }
 
-// log generates the output. It is always at the same stack depth. log inserts
-// indentation and the final newline if necessary. It prefixes the string
-// with the file and line of the call site.
+// log generates the output. It's always at the same stack depth.
 func (c *common) log(s string) {
-	s = strings.TrimSuffix(s, "\n")
-
-	// Second and subsequent lines are indented 4 spaces. This is in addition to
-	// the indentation provided by outputWriter.
-	s = strings.ReplaceAll(s, "\n", "\n"+indent)
-	s += "\n"
-
-	n := c.destination()
-	if n == nil {
-		// The test and all its parents are done. The log cannot be output.
-		panic("Log in goroutine after " + c.name + " has completed: " + s)
-	}
-
-	// Prefix with the call site. It is located by skipping 3 functions:
-	// callSite + log + public function
-	s = n.callSite(3) + s
-
-	// Output buffered logs.
-	n.flushPartial()
-
-	n.o.Write([]byte(s))
-}
-
-// destination selects the test to which output should be appended. It returns the
-// test if it is incomplete. Otherwise, it finds its closest incomplete parent.
-func (c *common) destination() *common {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
-	if !c.done {
-		return c
-	}
-	for parent := c.parent; parent != nil; parent = parent.parent {
-		parent.mu.Lock()
-		defer parent.mu.Unlock()
-		if !parent.done {
-			return parent
-		}
-	}
-	return nil
+	c.logDepth(s, 3) // logDepth + log + public function
 }
 
-// callSite retrieves and formats the file and line of the call site.
-func (c *common) callSite(skip int) string {
+// logDepth generates the output at an arbitrary stack depth.
+func (c *common) logDepth(s string, depth int) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
-
-	frame := c.frameSkip(skip)
-	file := frame.File
-	line := frame.Line
-	if file != "" {
-		if *fullPath {
-			// If relative path, truncate file name at last file name separator.
-		} else {
-			file = filepath.Base(file)
+	if c.done {
+		// This test has already finished. Try and log this message
+		// with our parent. If we don't have a parent, panic.
+		for parent := c.parent; parent != nil; parent = parent.parent {
+			parent.mu.Lock()
+			defer parent.mu.Unlock()
+			if !parent.done {
+				parent.output = append(parent.output, parent.decorate(s, depth+1)...)
+				return
+			}
 		}
+		panic("Log in goroutine after " + c.name + " has completed: " + s)
 	} else {
-		file = "???"
-	}
-	if line == 0 {
-		line = 1
-	}
-
-	return fmt.Sprintf("%s:%d: ", file, line)
-}
-
-// flushPartial checks the buffer for partial logs and outputs them.
-func (c *common) flushPartial() {
-	partial := func() bool {
-		c.mu.Lock()
-		defer c.mu.Unlock()
-		return (c.o != nil) && (len(c.o.partial) > 0)
-	}
-
-	if partial() {
-		c.o.Write([]byte("\n"))
-	}
-}
-
-// Output returns a Writer that writes to the same test output stream as TB.Log.
-// The output is indented like TB.Log lines, but Output does not
-// add source locations or newlines. The output is internally line
-// buffered, and a call to TB.Log or the end of the test will implicitly
-// flush the buffer, followed by a newline. After a test function and all its
-// parents return, neither Output nor the Write method may be called.
-func (c *common) Output() io.Writer {
-	c.checkFuzzFn("Output")
-	n := c.destination()
-	if n == nil {
-		panic("Output called after " + c.name + " has completed")
-	}
-	return n.o
-}
-
-// setOutputWriter initializes an outputWriter and sets it as a common field.
-func (c *common) setOutputWriter() {
-	c.o = &outputWriter{c: c}
-}
-
-// outputWriter buffers, formats and writes log messages.
-type outputWriter struct {
-	c       *common
-	partial []byte // incomplete ('\n'-free) suffix of last Write
-}
-
-// Write writes a log message to the test's output stream, properly formatted and
-// indented. It may not be called after a test function and all its parents return.
-func (o *outputWriter) Write(p []byte) (int, error) {
-	if o.c.destination() == nil {
-		panic("Write called after " + o.c.name + " has completed")
-	}
-
-	o.c.mu.Lock()
-	defer o.c.mu.Unlock()
-
-	// The last element is a partial line.
-	lines := bytes.SplitAfter(p, []byte("\n"))
-	last := len(lines) - 1 // Inv: 0 <= last
-	for i, line := range lines[:last] {
-		// Emit partial line from previous call.
-		if i == 0 && len(o.partial) > 0 {
-			line = slices.Concat(o.partial, line)
-			o.partial = o.partial[:0]
-		}
-		o.writeLine(line)
-	}
-	// Save partial line for next call.
-	o.partial = append(o.partial, lines[last]...)
-
-	return len(p), nil
-}
+		if c.chatty != nil {
+			if c.bench {
+				// Benchmarks don't print === CONT, so we should skip the test
+				// printer and just print straight to stdout.
+				fmt.Print(c.decorate(s, depth+1))
+			} else {
+				c.chatty.Printf(c.name, "%s", c.decorate(s, depth+1))
+			}
 
-// writeLine generates the output for a given line.
-func (o *outputWriter) writeLine(b []byte) {
-	if !o.c.done && (o.c.chatty != nil) {
-		if o.c.bench {
-			// Benchmarks don't print === CONT, so we should skip the test
-			// printer and just print straight to stdout.
-			fmt.Printf("%s%s", indent, b)
-		} else {
-			o.c.chatty.Printf(o.c.name, "%s%s", indent, b)
+			return
 		}
-		return
+		c.output = append(c.output, c.decorate(s, depth+1)...)
 	}
-	o.c.output = append(o.c.output, indent...)
-	o.c.output = append(o.c.output, b...)
 }
 
 // Log formats its arguments using default formatting, analogous to [fmt.Println],
@@ -1818,8 +1739,6 @@ func tRunner(t *T, fn func(t *T)) {
 				root.duration += highPrecisionTimeSince(root.start)
 				d := root.duration
 				root.mu.Unlock()
-				// Output buffered logs.
-				root.flushPartial()
 				root.flushToParent(root.name, "--- FAIL: %s (%s)\n", root.name, fmtDuration(d))
 				if r := root.parent.runCleanup(recoverAndReturnPanic); r != nil {
 					fmt.Fprintf(root.parent.w, "cleanup panicked with %v", r)
@@ -1867,10 +1786,6 @@ func tRunner(t *T, fn func(t *T)) {
 			// test. See comment in Run method.
 			t.tstate.release()
 		}
-		// Output buffered logs.
-		for root := &t.common; root.parent != nil; root = root.parent {
-			root.flushPartial()
-		}
 		t.report() // Report after all subtests have finished.
 
 		// Do not lock t.done to allow race detector to detect race in case
@@ -1936,7 +1851,6 @@ func (t *T) Run(name string, f func(t *T)) bool {
 		tstate: t.tstate,
 	}
 	t.w = indenter{&t.common}
-	t.setOutputWriter()
 
 	if t.chatty != nil {
 		t.chatty.Updatef(t.name, "=== RUN   %s\n", t.name)