crypto/tls: make -update only regenerate transcripts for failing tests

Change-Id: Ie68fd4fe2879e6b5417a1a4240971e3d837bf115
Reviewed-on: https://go-review.googlesource.com/c/go/+/204377
Run-TryBot: Filippo Valsorda <filippo@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
Reviewed-by: Katie Hockman <katie@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/crypto/tls/handshake_client_test.go

@@ -499,21 +499,15 @@ func peekError(conn net.Conn) error {
 }
 
 func runClientTestForVersion(t *testing.T, template *clientTest, version, option string) {
-	t.Run(version, func(t *testing.T) {
-		// Make a deep copy of the template before going parallel.
-		test := *template
-		if template.config != nil {
-			test.config = template.config.Clone()
-		}
-
-		if !*update {
-			t.Parallel()
-		}
+	// Make a deep copy of the template before going parallel.
+	test := *template
+	if template.config != nil {
+		test.config = template.config.Clone()
+	}
+	test.name = version + "-" + test.name
+	test.args = append([]string{option}, test.args...)
 
-		test.name = version + "-" + test.name
-		test.args = append([]string{option}, test.args...)
-		test.run(t, *update)
-	})
+	runTestAndUpdateIfNeeded(t, version, test.run, false)
 }
 
 func runClientTestTLS10(t *testing.T, template *clientTest) {

src/crypto/tls/handshake_server_test.go

@@ -729,25 +729,19 @@ func (test *serverTest) run(t *testing.T, write bool) {
 }
 
 func runServerTestForVersion(t *testing.T, template *serverTest, version, option string) {
-	t.Run(version, func(t *testing.T) {
-		// Make a deep copy of the template before going parallel.
-		test := *template
-		if template.config != nil {
-			test.config = template.config.Clone()
-		}
-
-		if !*update && !template.wait {
-			t.Parallel()
-		}
+	// Make a deep copy of the template before going parallel.
+	test := *template
+	if template.config != nil {
+		test.config = template.config.Clone()
+	}
+	test.name = version + "-" + test.name
+	if len(test.command) == 0 {
+		test.command = defaultClientCommand
+	}
+	test.command = append([]string(nil), test.command...)
+	test.command = append(test.command, option)
 
-		test.name = version + "-" + test.name
-		if len(test.command) == 0 {
-			test.command = defaultClientCommand
-		}
-		test.command = append([]string(nil), test.command...)
-		test.command = append(test.command, option)
-		test.run(t, *update)
-	})
+	runTestAndUpdateIfNeeded(t, version, test.run, test.wait)
 }
 
 func runServerTestTLS10(t *testing.T, template *serverTest) {

src/crypto/tls/handshake_test.go

@@ -37,17 +37,31 @@ import (
 // implementation.
 //
 // Tests can be updated by running them with the -update flag. This will cause
-// the test files to be regenerated. Generally one should combine the -update
-// flag with -test.run to updated a specific test. Since the reference
-// implementation will always generate fresh random numbers, large parts of
-// the reference connection will always change.
+// the test files for failing tests to be regenerated. Since the reference
+// implementation will always generate fresh random numbers, large parts of the
+// reference connection will always change.
 
 var (
-	update  = flag.Bool("update", false, "update golden files on disk")
+	update  = flag.Bool("update", false, "update golden files on failure")
 	fast    = flag.Bool("fast", false, "impose a quick, possibly flaky timeout on recorded tests")
 	keyFile = flag.String("keylog", "", "destination file for KeyLogWriter")
 )
 
+func runTestAndUpdateIfNeeded(t *testing.T, name string, run func(t *testing.T, update bool), wait bool) {
+	success := t.Run(name, func(t *testing.T) {
+		if !*update && !wait {
+			t.Parallel()
+		}
+		run(t, false)
+	})
+
+	if !success && *update {
+		t.Run(name+"#update", func(t *testing.T) {
+			run(t, true)
+		})
+	}
+}
+
 // checkOpenSSLVersion ensures that the version of OpenSSL looks reasonable
 // before updating the test data.
 func checkOpenSSLVersion() error {