testing: harmonize handling of prefix-matched benchmarks

If you have BenchmarkX1 with sub-benchmark Y
and you have BenchmarkX2 with no sub-benchmarks,
then

	go test -bench=X/Y

runs BenchmarkX1 once with b.N=1 (to find out about Y)
and then not again, because it has sub-benchmarks,
but arguably also because we're interested in Y.

In contrast, it runs BenchmarkX2 in full, even though clearly
that is not relevant to the match X/Y. We do have to run X2
once with b.N=1 to probe for having X2/Y, but we should not
run it with larger b.N.

Fixes #20589.

Change-Id: Ib86907e844f34dcaac6cd05757f57db1019201d0
Reviewed-on: https://go-review.googlesource.com/46031
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>

8 files changed, 142 insertions, 43 deletions

diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index a59da8bc90..e7fc5fc103 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -4194,3 +4194,61 @@ func main() {}`)
 		tg.setenv("GOARM", "7")
 	}))
 }
+
+func TestTestRegexps(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.setenv("GOPATH", filepath.Join(tg.pwd(), "testdata"))
+	tg.run("test", "-cpu=1", "-run=X/Y", "-bench=X/Y", "-count=2", "-v", "testregexp")
+	var lines []string
+	for _, line := range strings.SplitAfter(tg.getStdout(), "\n") {
+		if strings.Contains(line, "=== RUN") || strings.Contains(line, "--- BENCH") || strings.Contains(line, "LOG") {
+			lines = append(lines, line)
+		}
+	}
+
+	// Important parts:
+	//	TestX is run, twice
+	//	TestX/Y is run, twice
+	//	TestXX is run, twice
+	//	TestZ is not run
+	//	BenchmarkX is run but only with N=1, once
+	//	BenchmarkXX is run but only with N=1, once
+	//	BenchmarkX/Y is run in full, twice
+	want := `=== RUN   TestX
+=== RUN   TestX/Y
+	x_test.go:6: LOG: X running
+    	x_test.go:8: LOG: Y running
+=== RUN   TestXX
+	z_test.go:10: LOG: XX running
+=== RUN   TestX
+=== RUN   TestX/Y
+	x_test.go:6: LOG: X running
+    	x_test.go:8: LOG: Y running
+=== RUN   TestXX
+	z_test.go:10: LOG: XX running
+--- BENCH: BenchmarkX/Y
+	x_test.go:15: LOG: Y running N=1
+	x_test.go:15: LOG: Y running N=100
+	x_test.go:15: LOG: Y running N=10000
+	x_test.go:15: LOG: Y running N=1000000
+	x_test.go:15: LOG: Y running N=100000000
+	x_test.go:15: LOG: Y running N=2000000000
+--- BENCH: BenchmarkX/Y
+	x_test.go:15: LOG: Y running N=1
+	x_test.go:15: LOG: Y running N=100
+	x_test.go:15: LOG: Y running N=10000
+	x_test.go:15: LOG: Y running N=1000000
+	x_test.go:15: LOG: Y running N=100000000
+	x_test.go:15: LOG: Y running N=2000000000
+--- BENCH: BenchmarkX
+	x_test.go:13: LOG: X running N=1
+--- BENCH: BenchmarkXX
+	z_test.go:18: LOG: XX running N=1
+`
+
+	have := strings.Join(lines, "")
+	if have != want {
+		t.Errorf("reduced output:<<<\n%s>>> want:<<<\n%s>>>", have, want)
+	}
+}
diff --git a/src/cmd/go/testdata/src/testregexp/x_test.go b/src/cmd/go/testdata/src/testregexp/x_test.go
new file mode 100644
index 0000000000..7573e79e16
--- /dev/null
+++ b/src/cmd/go/testdata/src/testregexp/x_test.go
@@ -0,0 +1,17 @@
+package x
+
+import "testing"
+
+func TestX(t *testing.T) {
+	t.Logf("LOG: X running")
+	t.Run("Y", func(t *testing.T) {
+		t.Logf("LOG: Y running")
+	})
+}
+
+func BenchmarkX(b *testing.B) {
+	b.Logf("LOG: X running N=%d", b.N)
+	b.Run("Y", func(b *testing.B) {
+		b.Logf("LOG: Y running N=%d", b.N)
+	})
+}
diff --git a/src/cmd/go/testdata/src/testregexp/z_test.go b/src/cmd/go/testdata/src/testregexp/z_test.go
new file mode 100644
index 0000000000..4fd1979154
--- /dev/null
+++ b/src/cmd/go/testdata/src/testregexp/z_test.go
@@ -0,0 +1,19 @@
+package x
+
+import "testing"
+
+func TestZ(t *testing.T) {
+	t.Logf("LOG: Z running")
+}
+
+func TestXX(t *testing.T) {
+	t.Logf("LOG: XX running")
+}
+
+func BenchmarkZ(b *testing.B) {
+	b.Logf("LOG: Z running N=%d", b.N)
+}
+
+func BenchmarkXX(b *testing.B) {
+	b.Logf("LOG: XX running N=%d", b.N)
+}
diff --git a/src/testing/benchmark.go b/src/testing/benchmark.go
index 18a46d93bf..8b7f5cebaf 100644
--- a/src/testing/benchmark.go
+++ b/src/testing/benchmark.go
@@ -405,7 +405,7 @@ func runBenchmarks(importPath string, matchString func(pat, str string) (bool, e
 	}
 	var bs []InternalBenchmark
 	for _, Benchmark := range benchmarks {
-		if _, matched := ctx.match.fullName(nil, Benchmark.Name); matched {
+		if _, matched, _ := ctx.match.fullName(nil, Benchmark.Name); matched {
 			bs = append(bs, Benchmark)
 			benchName := benchmarkName(Benchmark.Name, maxprocs)
 			if l := len(benchName) + ctx.extLen + 1; l > ctx.maxLen {
@@ -492,9 +492,9 @@ func (b *B) Run(name string, f func(b *B)) bool {
 	benchmarkLock.Unlock()
 	defer benchmarkLock.Lock()
 
-	benchName, ok := b.name, true
+	benchName, ok, partial := b.name, true, false
 	if b.context != nil {
-		benchName, ok = b.context.match.fullName(&b.common, name)
+		benchName, ok, partial = b.context.match.fullName(&b.common, name)
 	}
 	if !ok {
 		return true
@@ -513,6 +513,11 @@ func (b *B) Run(name string, f func(b *B)) bool {
 		benchTime:  b.benchTime,
 		context:    b.context,
 	}
+	if partial {
+		// Partial name match, like -bench=X/Y matching BenchmarkX.
+		// Only process sub-benchmarks, if any.
+		atomic.StoreInt32(&sub.hasSub, 1)
+	}
 	if sub.run1() {
 		sub.run()
 	}
diff --git a/src/testing/match.go b/src/testing/match.go
index 7751035760..89e30d01a7 100644
--- a/src/testing/match.go
+++ b/src/testing/match.go
@@ -47,7 +47,7 @@ func newMatcher(matchString func(pat, str string) (bool, error), patterns, name
 	}
 }
 
-func (m *matcher) fullName(c *common, subname string) (name string, ok bool) {
+func (m *matcher) fullName(c *common, subname string) (name string, ok, partial bool) {
 	name = subname
 
 	m.mu.Lock()
@@ -62,15 +62,16 @@ func (m *matcher) fullName(c *common, subname string) (name string, ok bool) {
 
 	// We check the full array of paths each time to allow for the case that
 	// a pattern contains a '/'.
-	for i, s := range strings.Split(name, "/") {
+	elem := strings.Split(name, "/")
+	for i, s := range elem {
 		if i >= len(m.filter) {
 			break
 		}
 		if ok, _ := m.matchFunc(m.filter[i], s); !ok {
-			return name, false
+			return name, false, false
 		}
 	}
-	return name, true
+	return name, true, len(elem) < len(m.filter)
 }
 
 func splitRegexp(s string) []string {
diff --git a/src/testing/match_test.go b/src/testing/match_test.go
index 8c1c5f4452..8c09dc660f 100644
--- a/src/testing/match_test.go
+++ b/src/testing/match_test.go
@@ -88,43 +88,44 @@ func TestMatcher(t *T) {
 		pattern     string
 		parent, sub string
 		ok          bool
+		partial     bool
 	}{
 		// Behavior without subtests.
-		{"", "", "TestFoo", true},
-		{"TestFoo", "", "TestFoo", true},
-		{"TestFoo/", "", "TestFoo", true},
-		{"TestFoo/bar/baz", "", "TestFoo", true},
-		{"TestFoo", "", "TestBar", false},
-		{"TestFoo/", "", "TestBar", false},
-		{"TestFoo/bar/baz", "", "TestBar/bar/baz", false},
+		{"", "", "TestFoo", true, false},
+		{"TestFoo", "", "TestFoo", true, false},
+		{"TestFoo/", "", "TestFoo", true, true},
+		{"TestFoo/bar/baz", "", "TestFoo", true, true},
+		{"TestFoo", "", "TestBar", false, false},
+		{"TestFoo/", "", "TestBar", false, false},
+		{"TestFoo/bar/baz", "", "TestBar/bar/baz", false, false},
 
 		// with subtests
-		{"", "TestFoo", "x", true},
-		{"TestFoo", "TestFoo", "x", true},
-		{"TestFoo/", "TestFoo", "x", true},
-		{"TestFoo/bar/baz", "TestFoo", "bar", true},
+		{"", "TestFoo", "x", true, false},
+		{"TestFoo", "TestFoo", "x", true, false},
+		{"TestFoo/", "TestFoo", "x", true, false},
+		{"TestFoo/bar/baz", "TestFoo", "bar", true, true},
 		// Subtest with a '/' in its name still allows for copy and pasted names
 		// to match.
-		{"TestFoo/bar/baz", "TestFoo", "bar/baz", true},
-		{"TestFoo/bar/baz", "TestFoo/bar", "baz", true},
-		{"TestFoo/bar/baz", "TestFoo", "x", false},
-		{"TestFoo", "TestBar", "x", false},
-		{"TestFoo/", "TestBar", "x", false},
-		{"TestFoo/bar/baz", "TestBar", "x/bar/baz", false},
+		{"TestFoo/bar/baz", "TestFoo", "bar/baz", true, false},
+		{"TestFoo/bar/baz", "TestFoo/bar", "baz", true, false},
+		{"TestFoo/bar/baz", "TestFoo", "x", false, false},
+		{"TestFoo", "TestBar", "x", false, false},
+		{"TestFoo/", "TestBar", "x", false, false},
+		{"TestFoo/bar/baz", "TestBar", "x/bar/baz", false, false},
 
 		// subtests only
-		{"", "TestFoo", "x", true},
-		{"/", "TestFoo", "x", true},
-		{"./", "TestFoo", "x", true},
-		{"./.", "TestFoo", "x", true},
-		{"/bar/baz", "TestFoo", "bar", true},
-		{"/bar/baz", "TestFoo", "bar/baz", true},
-		{"//baz", "TestFoo", "bar/baz", true},
-		{"//", "TestFoo", "bar/baz", true},
-		{"/bar/baz", "TestFoo/bar", "baz", true},
-		{"//foo", "TestFoo", "bar/baz", false},
-		{"/bar/baz", "TestFoo", "x", false},
-		{"/bar/baz", "TestBar", "x/bar/baz", false},
+		{"", "TestFoo", "x", true, false},
+		{"/", "TestFoo", "x", true, false},
+		{"./", "TestFoo", "x", true, false},
+		{"./.", "TestFoo", "x", true, false},
+		{"/bar/baz", "TestFoo", "bar", true, true},
+		{"/bar/baz", "TestFoo", "bar/baz", true, false},
+		{"//baz", "TestFoo", "bar/baz", true, false},
+		{"//", "TestFoo", "bar/baz", true, false},
+		{"/bar/baz", "TestFoo/bar", "baz", true, false},
+		{"//foo", "TestFoo", "bar/baz", false, false},
+		{"/bar/baz", "TestFoo", "x", false, false},
+		{"/bar/baz", "TestBar", "x/bar/baz", false, false},
 	}
 
 	for _, tc := range testCases {
@@ -134,9 +135,9 @@ func TestMatcher(t *T) {
 		if tc.parent != "" {
 			parent.level = 1
 		}
-		if n, ok := m.fullName(parent, tc.sub); ok != tc.ok {
-			t.Errorf("for pattern %q, fullName(parent=%q, sub=%q) = %q, ok %v; want ok %v",
-				tc.pattern, tc.parent, tc.sub, n, ok, tc.ok)
+		if n, ok, partial := m.fullName(parent, tc.sub); ok != tc.ok || partial != tc.partial {
+			t.Errorf("for pattern %q, fullName(parent=%q, sub=%q) = %q, ok %v partial %v; want ok %v partial %v",
+				tc.pattern, tc.parent, tc.sub, n, ok, partial, tc.ok, tc.partial)
 		}
 	}
 }
@@ -178,7 +179,7 @@ func TestNaming(t *T) {
 	}
 
 	for i, tc := range testCases {
-		if got, _ := m.fullName(parent, tc.name); got != tc.want {
+		if got, _, _ := m.fullName(parent, tc.name); got != tc.want {
 			t.Errorf("%d:%s: got %q; want %q", i, tc.name, got, tc.want)
 		}
 	}
diff --git a/src/testing/sub_test.go b/src/testing/sub_test.go
index ab145b5bf4..af2d39c5be 100644
--- a/src/testing/sub_test.go
+++ b/src/testing/sub_test.go
@@ -7,7 +7,6 @@ package testing
 import (
 	"bytes"
 	"fmt"
-	"os"
 	"regexp"
 	"runtime"
 	"strings"
@@ -602,7 +601,6 @@ func TestBenchmark(t *T) {
 	res := Benchmark(func(b *B) {
 		for i := 0; i < 5; i++ {
 			b.Run("", func(b *B) {
-				fmt.Fprintf(os.Stderr, "b.N: %v\n", b.N)
 				for i := 0; i < b.N; i++ {
 					time.Sleep(time.Millisecond)
 				}
diff --git a/src/testing/testing.go b/src/testing/testing.go
index fa6c36c6d3..96c34a5aea 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -763,7 +763,7 @@ func tRunner(t *T, fn func(t *T)) {
 // must happen before the outer test function for t returns.
 func (t *T) Run(name string, f func(t *T)) bool {
 	atomic.StoreInt32(&t.hasSub, 1)
-	testName, ok := t.context.match.fullName(&t.common, name)
+	testName, ok, _ := t.context.match.fullName(&t.common, name)
 	if !ok {
 		return true
 	}