Add outputWriter as a common field

Author: suntala

src/testing/benchmark.go

@@ -675,6 +675,7 @@ func (s *benchState) processBench(b *B) {
 					benchFunc: b.benchFunc,
 					benchTime: b.benchTime,
 				}
+				b.o = &outputWriter{&b.common, nil}
 				b.run1()
 			}
 			r := b.doBench()
@@ -751,6 +752,7 @@ func (b *B) Run(name string, f func(b *B)) bool {
 		benchTime:  b.benchTime,
 		bstate:     b.bstate,
 	}
+	sub.o = &outputWriter{&sub.common, nil}
 	if partial {
 		// Partial name match, like -bench=X/Y matching BenchmarkX.
 		// Only process sub-benchmarks, if any.
@@ -927,6 +929,7 @@ func Benchmark(f func(b *B)) BenchmarkResult {
 		benchFunc: f,
 		benchTime: benchTime,
 	}
+	b.o = &outputWriter{&b.common, nil}
 	if b.run1() {
 		b.run()
 	}

src/testing/fuzz.go

@@ -320,6 +320,7 @@ func (f *F) Fuzz(ff any) {
 			t.parent.w = captureOut
 		}
 		t.w = indenter{&t.common}
+		t.o = &outputWriter{&t.common, nil}
 		if t.chatty != nil {
 			t.chatty.Updatef(t.name, "=== RUN   %s\n", t.name)
 		}
@@ -529,6 +530,7 @@ func runFuzzTests(deps testDeps, fuzzTests []InternalFuzzTarget, deadline time.T
 					fstate: fstate,
 				}
 				f.w = indenter{&f.common}
+				f.o = &outputWriter{&f.common, nil}
 				if f.chatty != nil {
 					f.chatty.Updatef(f.name, "=== RUN   %s\n", f.name)
 				}

src/testing/testing.go

@@ -626,6 +626,7 @@ 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           io.Writer            // 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.
@@ -1007,17 +1008,18 @@ func (c *common) FailNow() {
 // indentation and the final newline if necessary. It prefixes the string
 // with the file and line of the call site.
 func (c *common) log(s string) {
-	if l := len(s); l > 0 && (string(s[l-1]) != "\n") {
-		s += "\n"
+	if l := len(s); l > 0 && (string(s[l-1]) == "\n") {
+		s = s[:l-1]
 	}
 	// Second and subsequent lines are indented 4 spaces. This is in addition to
 	// the indentation provided by outputWriter.
 	s = strings.Replace(s, "\n", "\n    ", -1)
+	s += "\n"
 
 	// Prefix with the call site. It is located by skipping 3 functions:
 	// callSite + log + public function
 	s = c.callSite(3) + s
-	c.newOutputWriter().Write([]byte(s))
+	c.o.Write([]byte(s))
 }
 
 // callSite retrieves and formats the file and line of the call site.
@@ -1881,6 +1883,7 @@ func (t *T) Run(name string, f func(t *T)) bool {
 		tstate: t.tstate,
 	}
 	t.w = indenter{&t.common}
+	t.o = &outputWriter{&t.common, nil}
 
 	if t.chatty != nil {
 		t.chatty.Updatef(t.name, "=== RUN   %s\n", t.name)