Make ToGoName prefix configurable when first char is not a letter

This will allow go-swagger to plus in here its pascalize func and
contribute fixing go-swagger/go-swagger#1937 (inconsistent naming rules)

Signed-off-by: Frederic BIDON <[email protected]>

util.go

@@ -16,6 +16,7 @@ package swag
 
 import (
 	"reflect"
+	"regexp"
 	"strings"
 	"unicode"
 )
@@ -28,6 +29,20 @@ var initialisms []string
 
 var isInitialism func(string) bool
 
+var (
+	splitRex1     *regexp.Regexp
+	splitRex2     *regexp.Regexp
+	splitReplacer *strings.Replacer
+)
+
+// GoNamePrefixFunc sets an optional rule to prefix go names
+// which do not start with a letter.
+//
+// e.g. to help converting "123" into "{prefix}123"
+//
+// The default is to prefix with "X"
+var GoNamePrefixFunc func(string) string
+
 func init() {
 	// Taken from https://github.com/golang/lint/blob/3390df4df2787994aea98de825b964ac7944b817/lint.go#L732-L769
 	var configuredInitialisms = map[string]bool{
@@ -291,7 +306,10 @@ func ToGoName(name string) string {
 		// Only prefix with X when the first character isn't an ascii letter
 		first := []rune(result)[0]
 		if !unicode.IsLetter(first) || (first > unicode.MaxASCII && !unicode.IsUpper(first)) {
-			result = "X" + result
+			if GoNamePrefixFunc == nil {
+				return "X" + result
+			}
+			result = GoNamePrefixFunc(name) + result
 		}
 		first = []rune(result)[0]
 		if unicode.IsLetter(first) && !unicode.IsUpper(first) {

util_test.go

@@ -16,13 +16,14 @@ package swag
 
 import (
 	"fmt"
-	"github.com/stretchr/testify/require"
 	"log"
 	"strings"
 	"testing"
 	"time"
 	"unicode"
 
+	"github.com/stretchr/testify/require"
+
 	"github.com/stretchr/testify/assert"
 )
 
@@ -403,6 +404,7 @@ func TestCamelize(t *testing.T) {
 		{"ELB.HTTPLoadBalancer", "Elb.httploadbalancer"},
 		{"elbHTTPLoadBalancer", "Elbhttploadbalancer"},
 		{"ELBHTTPLoadBalancer", "Elbhttploadbalancer"},
+		{"12ab", "12ab"},
 	}
 
 	for _, sample := range samples {
@@ -455,3 +457,36 @@ func TestToVarName(t *testing.T) {
 		assert.Equalf(t, sample.out, res, "expected ToVarName(%q)=%q, got %q", sample.str, sample.out, res)
 	}
 }
+
+func TestToGoNameUnicode(t *testing.T) {
+	defer func() { GoNamePrefixFunc = nil }()
+	GoNamePrefixFunc = func(name string) string {
+		// this is the pascalize func from go-swagger codegen
+		arg := []rune(name)
+		if len(arg) == 0 || arg[0] > '9' {
+			return ""
+		}
+		if arg[0] == '+' {
+			return "Plus"
+		}
+		if arg[0] == '-' {
+			return "Minus"
+		}
+
+		return "Nr"
+	}
+
+	samples := []translationSample{
+		{"123_a", "Nr123a"},
+		{"!123_a", "Bang123a"},
+		{"+123_a", "Plus123a"},
+		{"abc", "Abc"},
+		{"éabc", "Éabc"},
+		{":éabc", "Éabc"},
+		// TODO: non unicode char
+	}
+
+	for _, sample := range samples {
+		assert.Equal(t, sample.out, ToGoName(sample.str))
+	}
+}