fix #423 : Add helper function and some documentation to parse shorthand go test flags.

Author: valdar

README.md

@@ -284,6 +284,26 @@ func main() {
 }
 ```
 
+### Using pflag with go test
+`pflag` skips parsing of shorthand version of go test specific flags (i.e. the one passed as `-test.`)
+See issues: [#63](https://github.com/spf13/pflag/issues/63) and [#238](https://github.com/spf13/pflag/issues/238) for more details.
+
+**Example**: You want to separately parse go test flags anyway
+```go
+import (
+	goflag "flag"
+	flag "github.com/spf13/pflag"
+)
+
+var ip *int = flag.Int("flagname", 1234, "help message for flagname")
+
+func main() {
+	flag.CommandLine.AddGoFlagSet(goflag.CommandLine)
+    ParseGoTestFlags(os.Args[1:], goflag.CommandLine)
+	flag.Parse()
+}
+```
+
 ## More info
 
 You can see the full reference documentation of the pflag package

golangflag.go

@@ -103,3 +103,15 @@ func (f *FlagSet) AddGoFlagSet(newSet *goflag.FlagSet) {
 	}
 	f.addedGoFlagSets = append(f.addedGoFlagSets, newSet)
 }
+
+// ParseGoTestFlags Parses go test flags (i.e. the one with '-test.') separately because pflag.Parse() skip  flags with '-test.' prefix
+// Typical usage example: `ParseGoTestFlags(os.Args[1:], goflag.CommandLine)`
+func ParseGoTestFlags(osArgs []string, goFlagSet *goflag.FlagSet) error {
+	var goTestFlags []string
+	for _, f := range osArgs {
+		if strings.HasPrefix(f, "-test.") {
+			goTestFlags = append(goTestFlags, f)
+		}
+	}
+	return goFlagSet.Parse(goTestFlags)
+}

golangflag_test.go

@@ -12,11 +12,14 @@ import (
 func TestGoflags(t *testing.T) {
 	goflag.String("stringFlag", "stringFlag", "stringFlag")
 	goflag.Bool("boolFlag", false, "boolFlag")
+	var testxxxValue string
+	goflag.StringVar(&testxxxValue, "test.xxx", "test.xxx", "it is a test flag")
 
 	f := NewFlagSet("test", ContinueOnError)
 
 	f.AddGoFlagSet(goflag.CommandLine)
-	err := f.Parse([]string{"--stringFlag=bob", "--boolFlag"})
+	args := []string{"--stringFlag=bob", "--boolFlag", "-test.xxx=testvalue"}
+	err := f.Parse(args)
 	if err != nil {
 		t.Fatal("expected no error; get", err)
 	}
@@ -40,6 +43,17 @@ func TestGoflags(t *testing.T) {
 		t.Fatal("f.Parsed() return false after f.Parse() called")
 	}
 
+	if testxxxValue != "test.xxx" {
+		t.Fatalf("expected testxxxValue to be test.xxx but got %v", testxxxValue)
+	}
+	err = ParseGoTestFlags(args, goflag.CommandLine)
+	if err != nil {
+		t.Fatal("expected no error; ParseGoTestFlags", err)
+	}
+	if testxxxValue != "testvalue" {
+		t.Fatalf("expected testxxxValue to be testvalue but got %v", testxxxValue)
+	}
+
 	// in fact it is useless. because `go test` called flag.Parse()
 	if !goflag.CommandLine.Parsed() {
 		t.Fatal("goflag.CommandLine.Parsed() return false after f.Parse() called")