cmd/vet: parallelize tests

Was 2.3 seconds. Now 1.4 seconds.

Next win would be not running a child process and refactoring main so
it could be called from tests easily. But that would also require
rewriting the errchk written in Perl. This appears to be the last user
of errchk in the tree.

Updates #17751

Change-Id: Id7c3cec76f438590789b994e756f55b5397be07f
Reviewed-on: https://go-review.googlesource.com/32754
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

15 files changed, 92 insertions, 34 deletions

diff --git a/src/cmd/vet/testdata/asm.go b/src/cmd/vet/testdata/asm/asm.go
index e6d6d03106..e6d6d03106 100644
--- a/src/cmd/vet/testdata/asm.go
+++ b/src/cmd/vet/testdata/asm/asm.go
diff --git a/src/cmd/vet/testdata/asm1.s b/src/cmd/vet/testdata/asm/asm1.s
index cac6ed22cd..cac6ed22cd 100644
--- a/src/cmd/vet/testdata/asm1.s
+++ b/src/cmd/vet/testdata/asm/asm1.s
diff --git a/src/cmd/vet/testdata/asm2.s b/src/cmd/vet/testdata/asm/asm2.s
index c33c02a70b..c33c02a70b 100644
--- a/src/cmd/vet/testdata/asm2.s
+++ b/src/cmd/vet/testdata/asm/asm2.s
diff --git a/src/cmd/vet/testdata/asm3.s b/src/cmd/vet/testdata/asm/asm3.s
index 3d69356a0f..3d69356a0f 100644
--- a/src/cmd/vet/testdata/asm3.s
+++ b/src/cmd/vet/testdata/asm/asm3.s
diff --git a/src/cmd/vet/testdata/asm4.s b/src/cmd/vet/testdata/asm/asm4.s
index 044b050b6b..044b050b6b 100644
--- a/src/cmd/vet/testdata/asm4.s
+++ b/src/cmd/vet/testdata/asm/asm4.s
diff --git a/src/cmd/vet/testdata/asm5.s b/src/cmd/vet/testdata/asm/asm5.s
index c6176e9669..c6176e9669 100644
--- a/src/cmd/vet/testdata/asm5.s
+++ b/src/cmd/vet/testdata/asm/asm5.s
diff --git a/src/cmd/vet/testdata/asm6.s b/src/cmd/vet/testdata/asm/asm6.s
index 4e85ab3dcf..4e85ab3dcf 100644
--- a/src/cmd/vet/testdata/asm6.s
+++ b/src/cmd/vet/testdata/asm/asm6.s
diff --git a/src/cmd/vet/testdata/asm7.s b/src/cmd/vet/testdata/asm/asm7.s
index d5ff5460a5..d5ff5460a5 100644
--- a/src/cmd/vet/testdata/asm7.s
+++ b/src/cmd/vet/testdata/asm/asm7.s
diff --git a/src/cmd/vet/testdata/buildtag.go b/src/cmd/vet/testdata/buildtag/buildtag.go
index f12f895dfb..f12f895dfb 100644
--- a/src/cmd/vet/testdata/buildtag.go
+++ b/src/cmd/vet/testdata/buildtag/buildtag.go
diff --git a/src/cmd/vet/testdata/buildtag_bad.go b/src/cmd/vet/testdata/buildtag/buildtag_bad.go
index fbe10cf748..fbe10cf748 100644
--- a/src/cmd/vet/testdata/buildtag_bad.go
+++ b/src/cmd/vet/testdata/buildtag/buildtag_bad.go
diff --git a/src/cmd/vet/testdata/cgo.go b/src/cmd/vet/testdata/cgo/cgo.go
index 25d395b1ea..25d395b1ea 100644
--- a/src/cmd/vet/testdata/cgo.go
+++ b/src/cmd/vet/testdata/cgo/cgo.go
diff --git a/src/cmd/vet/testdata/cgo2.go b/src/cmd/vet/testdata/cgo/cgo2.go
index 276aea9619..276aea9619 100644
--- a/src/cmd/vet/testdata/cgo2.go
+++ b/src/cmd/vet/testdata/cgo/cgo2.go
diff --git a/src/cmd/vet/testdata/testingpkg/tests.go b/src/cmd/vet/testdata/testingpkg/tests.go
new file mode 100644
index 0000000000..69d29d3c6c
--- /dev/null
+++ b/src/cmd/vet/testdata/testingpkg/tests.go
@@ -0,0 +1 @@
+package testdata
diff --git a/src/cmd/vet/testdata/tests_test.go b/src/cmd/vet/testdata/testingpkg/tests_test.go
index f5bbc3922a..f5bbc3922a 100644
--- a/src/cmd/vet/testdata/tests_test.go
+++ b/src/cmd/vet/testdata/testingpkg/tests_test.go
diff --git a/src/cmd/vet/vet_test.go b/src/cmd/vet/vet_test.go
index b4b909e0e2..853088d768 100644
--- a/src/cmd/vet/vet_test.go
+++ b/src/cmd/vet/vet_test.go
@@ -13,6 +13,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"runtime"
+	"sync"
 	"testing"
 )
 
@@ -40,19 +41,22 @@ func MustHavePerl(t *testing.T) {
 }
 
 var (
-	built  = false // We have built the binary.
-	failed = false // We have failed to build the binary, don't try again.
+	buildMu sync.Mutex // guards following
+	built   = false    // We have built the binary.
+	failed  = false    // We have failed to build the binary, don't try again.
 )
 
 func Build(t *testing.T) {
-	testenv.MustHaveGoBuild(t)
-	MustHavePerl(t)
+	buildMu.Lock()
+	defer buildMu.Unlock()
 	if built {
 		return
 	}
 	if failed {
 		t.Skip("cannot run on this environment")
 	}
+	testenv.MustHaveGoBuild(t)
+	MustHavePerl(t)
 	cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", binary)
 	output, err := cmd.CombinedOutput()
 	if err != nil {
@@ -83,69 +87,122 @@ func Vet(t *testing.T, files []string) {
 // 	rm testvet
 //
 
+// TestVet tests self-contained files in testdata/*.go.
+//
+// If a file contains assembly or has inter-dependencies, it should be
+// in its own test, like TestVetAsm, TestDivergentPackagesExamples,
+// etc below.
 func TestVet(t *testing.T) {
 	Build(t)
+	t.Parallel()
 
 	// errchk ./testvet
 	gos, err := filepath.Glob(filepath.Join(dataDir, "*.go"))
 	if err != nil {
 		t.Fatal(err)
 	}
-	asms, err := filepath.Glob(filepath.Join(dataDir, "*.s"))
-	if err != nil {
-		t.Fatal(err)
+	wide := runtime.GOMAXPROCS(0)
+	if wide > len(gos) {
+		wide = len(gos)
+	}
+	batch := make([][]string, wide)
+	for i, file := range gos {
+		batch[i%wide] = append(batch[i%wide], file)
+	}
+	for i, files := range batch {
+		files := files
+		t.Run(fmt.Sprint(i), func(t *testing.T) {
+			t.Parallel()
+			t.Logf("files: %q", files)
+			Vet(t, files)
+		})
 	}
-	files := append(gos, asms...)
-	Vet(t, files)
 }
 
-func TestDivergentPackagesExamples(t *testing.T) {
+func TestVetAsm(t *testing.T) {
 	Build(t)
+
+	asmDir := filepath.Join(dataDir, "asm")
+	gos, err := filepath.Glob(filepath.Join(asmDir, "*.go"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	asms, err := filepath.Glob(filepath.Join(asmDir, "*.s"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	t.Parallel()
 	// errchk ./testvet
-	Vet(t, []string{"testdata/divergent"})
+	Vet(t, append(gos, asms...))
 }
 
-func TestIncompleteExamples(t *testing.T) {
+func TestVetDirs(t *testing.T) {
+	t.Parallel()
 	Build(t)
-	// errchk ./testvet
-	Vet(t, []string{"testdata/incomplete/examples_test.go"})
+	for _, dir := range []string{
+		"testingpkg",
+		"divergent",
+		"buildtag",
+		"incomplete", // incomplete examples
+	} {
+		dir := dir
+		t.Run(dir, func(t *testing.T) {
+			t.Parallel()
+			gos, err := filepath.Glob(filepath.Join("testdata", dir, "*.go"))
+			if err != nil {
+				t.Fatal(err)
+			}
+			Vet(t, gos)
+		})
+	}
 }
 
 func run(c *exec.Cmd, t *testing.T) bool {
 	output, err := c.CombinedOutput()
-	os.Stderr.Write(output)
 	if err != nil {
+		t.Logf("vet output:\n%s", output)
 		t.Fatal(err)
 	}
 	// Errchk delights by not returning non-zero status if it finds errors, so we look at the output.
 	// It prints "BUG" if there is a failure.
 	if !c.ProcessState.Success() {
+		t.Logf("vet output:\n%s", output)
 		return false
 	}
-	return !bytes.Contains(output, []byte("BUG"))
+	ok := !bytes.Contains(output, []byte("BUG"))
+	if !ok {
+		t.Logf("vet output:\n%s", output)
+	}
+	return ok
 }
 
 // TestTags verifies that the -tags argument controls which files to check.
 func TestTags(t *testing.T) {
+	t.Parallel()
 	Build(t)
 	for _, tag := range []string{"testtag", "x testtag y", "x,testtag,y"} {
-		t.Logf("-tags=%s", tag)
-		args := []string{
-			"-tags=" + tag,
-			"-v", // We're going to look at the files it examines.
-			"testdata/tagtest",
-		}
-		cmd := exec.Command("./"+binary, args...)
-		output, err := cmd.CombinedOutput()
-		if err != nil {
-			t.Fatal(err)
-		}
-		// file1 has testtag and file2 has !testtag.
-		if !bytes.Contains(output, []byte(filepath.Join("tagtest", "file1.go"))) {
-			t.Error("file1 was excluded, should be included")
-		}
-		if bytes.Contains(output, []byte(filepath.Join("tagtest", "file2.go"))) {
-			t.Error("file2 was included, should be excluded")
-		}
+		tag := tag
+		t.Run(tag, func(t *testing.T) {
+			t.Parallel()
+			t.Logf("-tags=%s", tag)
+			args := []string{
+				"-tags=" + tag,
+				"-v", // We're going to look at the files it examines.
+				"testdata/tagtest",
+			}
+			cmd := exec.Command("./"+binary, args...)
+			output, err := cmd.CombinedOutput()
+			if err != nil {
+				t.Fatal(err)
+			}
+			// file1 has testtag and file2 has !testtag.
+			if !bytes.Contains(output, []byte(filepath.Join("tagtest", "file1.go"))) {
+				t.Error("file1 was excluded, should be included")
+			}
+			if bytes.Contains(output, []byte(filepath.Join("tagtest", "file2.go"))) {
+				t.Error("file2 was included, should be excluded")
+			}
+		})
 	}
 }