cmd/go: make 'go test -h' print two lines

Like every other command's -h flag. To achieve this, pass the command's
usage function to the cmdflag package, since that package is used by
multiple commands and cannot directly access *base.Command.

This also lets us get rid of testFlag1 and testFlag2, and instead have
contiguous raw strings for the test and testflag help docs.

Fixes #26999.

Change-Id: I2ebd66835ee61fa83270816a01fa312425224bb3
Reviewed-on: https://go-review.googlesource.com/c/144558
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

src/cmd/go/internal/cmdflag/flag.go

@@ -79,15 +79,15 @@ func AddKnownFlags(cmd string, defns []*Defn) {
 
 // Parse sees if argument i is present in the definitions and if so,
 // returns its definition, value, and whether it consumed an extra word.
-// If the flag begins (cmd+".") it is ignored for the purpose of this function.
-func Parse(cmd string, defns []*Defn, args []string, i int) (f *Defn, value string, extra bool) {
+// If the flag begins (cmd.Name()+".") it is ignored for the purpose of this function.
+func Parse(cmd string, usage func(), defns []*Defn, args []string, i int) (f *Defn, value string, extra bool) {
 	arg := args[i]
 	if strings.HasPrefix(arg, "--") { // reduce two minuses to one
 		arg = arg[1:]
 	}
 	switch arg {
 	case "-?", "-h", "-help":
-		base.Usage()
+		usage()
 	}
 	if arg == "" || arg[0] != '-' {
 		return

src/cmd/go/internal/test/test.go

@@ -124,16 +124,6 @@ A cached test result is treated as executing in no time at all,
 so a successful package test result will be cached and reused
 regardless of -timeout setting.
 
-` + strings.TrimSpace(testFlag1) + ` See 'go help testflag' for details.
-
-For more about build flags, see 'go help build'.
-For more about specifying packages, see 'go help packages'.
-
-See also: go build, go vet.
-`,
-}
-
-const testFlag1 = `
 In addition to the build flags, the flags handled by 'go test' itself are:
 
 	-args
@@ -164,15 +154,13 @@ In addition to the build flags, the flags handled by 'go test' itself are:
 	    The test still runs (unless -c or -i is specified).
 
 The test binary also accepts flags that control execution of the test; these
-flags are also accessible by 'go test'.
-`
+flags are also accessible by 'go test'. See 'go help testflag' for details.
 
-// Usage prints the usage message for 'go test -h' and exits.
-func Usage() {
-	os.Stderr.WriteString("usage: " + testUsage + "\n\n" +
-		strings.TrimSpace(testFlag1) + "\n\n\t" +
-		strings.TrimSpace(testFlag2) + "\n")
-	os.Exit(2)
+For more about build flags, see 'go help build'.
+For more about specifying packages, see 'go help packages'.
+
+See also: go build, go vet.
+`,
 }
 
 var HelpTestflag = &base.Command{
@@ -190,11 +178,6 @@ options of pprof control how the information is presented.
 The following flags are recognized by the 'go test' command and
 control the execution of any test:
 
-	` + strings.TrimSpace(testFlag2) + `
-`,
-}
-
-const testFlag2 = `
 	-bench regexp
 	    Run only those benchmarks matching a regular expression.
 	    By default, no benchmarks are run.
@@ -414,7 +397,8 @@ In the first example, the -x and the second -v are passed through to the
 test binary unchanged and with no effect on the go command itself.
 In the second example, the argument math is passed through to the test
 binary, instead of being interpreted as the package list.
-`
+`,
+}
 
 var HelpTestfunc = &base.Command{
 	UsageLine: "testfunc",
@@ -532,7 +516,7 @@ var testVetFlags = []string{
 func runTest(cmd *base.Command, args []string) {
 	modload.LoadTests = true
 
-	pkgArgs, testArgs = testFlags(args)
+	pkgArgs, testArgs = testFlags(cmd.Usage, args)
 
 	work.FindExecCmd() // initialize cached result
 

src/cmd/go/internal/test/testflag.go

@@ -87,7 +87,7 @@ func init() {
 // to allow both
 //	go test fmt -custom-flag-for-fmt-test
 //	go test -x math
-func testFlags(args []string) (packageNames, passToTest []string) {
+func testFlags(usage func(), args []string) (packageNames, passToTest []string) {
 	args = str.StringList(cmdflag.FindGOFLAGS(testFlagDefn), args)
 	inPkg := false
 	var explicitArgs []string
@@ -108,7 +108,7 @@ func testFlags(args []string) (packageNames, passToTest []string) {
 			inPkg = false
 		}
 
-		f, value, extraWord := cmdflag.Parse(cmd, testFlagDefn, args, i)
+		f, value, extraWord := cmdflag.Parse(cmd, usage, testFlagDefn, args, i)
 		if f == nil {
 			// This is a flag we do not know; we must assume
 			// that any args we see after this might be flag

src/cmd/go/internal/vet/vet.go

@@ -38,7 +38,7 @@ See also: go fmt, go fix.
 func runVet(cmd *base.Command, args []string) {
 	modload.LoadTests = true
 
-	vetFlags, pkgArgs := vetFlags(args)
+	vetFlags, pkgArgs := vetFlags(cmd.Usage, args)
 
 	work.BuildInit()
 	work.VetFlags = vetFlags

src/cmd/go/internal/vet/vetflag.go

@@ -40,7 +40,7 @@ var vetTool = os.Getenv("GOVETTOOL")
 
 // vetFlags processes the command line, splitting it at the first non-flag
 // into the list of flags and list of packages.
-func vetFlags(args []string) (passToVet, packageNames []string) {
+func vetFlags(usage func(), args []string) (passToVet, packageNames []string) {
 	// Query the vet command for its flags.
 	tool := vetTool
 	if tool != "" {
@@ -108,7 +108,7 @@ func vetFlags(args []string) (passToVet, packageNames []string) {
 			return args[:i], args[i:]
 		}
 
-		f, value, extraWord := cmdflag.Parse("vet", vetFlagDefn, args, i)
+		f, value, extraWord := cmdflag.Parse("vet", usage, vetFlagDefn, args, i)
 		if f == nil {
 			fmt.Fprintf(os.Stderr, "vet: flag %q not defined\n", args[i])
 			fmt.Fprintf(os.Stderr, "Run \"go help vet\" for more information\n")

src/cmd/go/main.go

@@ -235,17 +235,6 @@ func init() {
 }
 
 func mainUsage() {
-	// special case "go test -h"
-	if len(os.Args) > 1 && os.Args[1] == "test" {
-		test.Usage()
-	}
-	// Since vet shares code with test in cmdflag, it doesn't show its
-	// command usage properly. For now, special case it too.
-	// TODO(mvdan): fix the cmdflag package instead; see
-	// golang.org/issue/26999
-	if len(os.Args) > 1 && os.Args[1] == "vet" {
-		vet.CmdVet.Usage()
-	}
 	help.PrintUsage(os.Stderr, base.Go)
 	os.Exit(2)
 }

src/cmd/go/testdata/script/help.txt

@@ -35,7 +35,13 @@ stderr 'Run ''go help mod'' for usage.'
 stderr 'usage: go vet'
 stderr 'Run ''go help vet'' for details'
 
+# Earlier versions of Go printed a large document here, instead of these two
+# lines.
+! go test -h
+stderr 'usage: go test'
+stderr 'Run ''go help test'' for details'
+
 # go help get shows usage for get
 go help get
 stdout 'usage: go get'
-stdout 'get when using GOPATH'
+stdout 'get when using GOPATH'