Add support for prefixes

strcase/opt.go

@@ -14,7 +14,17 @@ type IndicatorFunc func(word string, idx int) bool
 
 // CaseOpts is a struct that holds the options for a CaseConverter.
 type CaseOpts struct {
-	vocab     []string
+	// A prefix to match before converting the string.
+	//
+	// Example:
+	//
+	// a. This is a sentence.
+	prefix string
+
+	// A list of words to specifying how to capitalize them.
+	vocab []string
+
+	// A function that determines whether or not a word should be capitalized.
 	indicator IndicatorFunc
 }
 
@@ -31,3 +41,10 @@ func UsingIndicator(indicator IndicatorFunc) CaseOptFunc {
 		opts.indicator = indicator
 	}
 }
+
+// UsingPrefix sets the prefix for the CaseConverter.
+func UsingPrefix(prefix string) CaseOptFunc {
+	return func(opts *CaseOpts) {
+		opts.prefix = prefix
+	}
+}

strcase/sentence.go

@@ -2,6 +2,7 @@ package strcase
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
 
 	"github.com/errata-ai/regexp2"
@@ -37,6 +38,7 @@ func NewSentenceConverter(opts ...CaseOptFunc) *SentenceConverter {
 
 	sent.vocab = base.vocab
 	sent.indicator = base.indicator
+	sent.prefix = base.prefix
 
 	return sent
 }
@@ -45,6 +47,14 @@ func NewSentenceConverter(opts ...CaseOptFunc) *SentenceConverter {
 func (sc *SentenceConverter) Convert(s string) string {
 	var made []string
 
+	prefix := ""
+	if sc.prefix != "" {
+		if prefixRe := regexp.MustCompile(sc.prefix); prefixRe.MatchString(s) {
+			prefix = prefixRe.FindString(s)
+			s = strings.TrimPrefix(s, prefix)
+		}
+	}
+
 	ps := `[\p{N}\p{L}*]+[^\s]*`
 	if len(sc.vocab) > 0 {
 		ps = fmt.Sprintf(`\b(?:%s)\b|%s`, strings.Join(sc.vocab, "|"), ps)
@@ -71,7 +81,7 @@ func (sc *SentenceConverter) Convert(s string) string {
 		}
 	}
 
-	return strings.Join(made, " ")
+	return prefix + strings.Join(made, " ")
 }
 
 func (sc *SentenceConverter) inVocab(s string) string {

strcase/sentence_test.go

@@ -21,6 +21,7 @@ var vocabCases = []testCase{
 	{"macOS 15: What's new", "macOS 15: What's new"},
 	{"Configuration", "Configuration"},
 	{"Six NASA Instruments Will Fly to Moon on Intuitive Machines Lander", "Six NASA instruments will fly to Moon on intuitive machines lander"},
+	{"b. Next title text", "b. Next title text"},
 }
 
 func TestSentence(t *testing.T) {
@@ -34,14 +35,16 @@ func TestSentence(t *testing.T) {
 }
 
 func TestVocab(t *testing.T) {
-	tc := strcase.NewSentenceConverter(strcase.UsingVocab([]string{
-		"Vale Server",
-		"\bI\b",
-		"macOS",
-		"[Cc]onfig",
-		"NASA",
-		"Moon",
-	}))
+	tc := strcase.NewSentenceConverter(
+		strcase.UsingVocab([]string{
+			"Vale Server",
+			"\bI\b",
+			"macOS",
+			"[Cc]onfig",
+			"NASA",
+			"Moon",
+		}),
+		strcase.UsingPrefix(`^[a-z]\.\s`))
 
 	for _, test := range vocabCases {
 		sent := tc.Convert(test.Input)

strcase/title.go

@@ -67,20 +67,29 @@ func NewTitleConverter(style IgnoreFunc, opts ...CaseOptFunc) *TitleConverter {
 
 	title.vocab = base.vocab
 	title.indicator = base.indicator
+	title.prefix = base.prefix
 
 	return title
 }
 
 // Convert returns a copy of the string s in title case format.
 func (tc *TitleConverter) Convert(s string) string {
+	prefix := ""
+	if tc.prefix != "" {
+		if prefixRe := regexp.MustCompile(tc.prefix); prefixRe.MatchString(s) {
+			prefix = prefixRe.FindString(s)
+			s = strings.TrimPrefix(s, prefix)
+		}
+	}
+
 	idx, pos := 0, 0
 	t := sanitizer.Replace(s)
 	end := len(t)
 
 	tags := tagger.Tag(splitRE.FindAllString(strings.ToLower(s), -1))
 	widx := -1
 
-	return splitRE.ReplaceAllStringFunc(s, func(m string) string {
+	return prefix + splitRE.ReplaceAllStringFunc(s, func(m string) string {
 		widx += 1
 
 		sm := strings.ToLower(m)

strcase/title_test.go

@@ -20,14 +20,17 @@ var vocabTitles = []testCase{
 	{"Getting started with iOS 15", "Getting Started With iOS 15"},
 	{"Understanding json and yaml", "Understanding JSON and YAML"},
 	{"Develop File-Proxy Plugin", "Develop File-Proxy Plugin"},
+	{"b. Next title text", "b. Next Title Text"},
 }
 
 func TestTitleVocab(t *testing.T) {
-	tc := strcase.NewTitleConverter(strcase.APStyle, strcase.UsingVocab([]string{
-		"iOS",
-		"JSON",
-		"YAML",
-	}))
+	tc := strcase.NewTitleConverter(strcase.APStyle,
+		strcase.UsingVocab([]string{
+			"iOS",
+			"JSON",
+			"YAML",
+		}),
+		strcase.UsingPrefix(`^[a-z]\.\s`))
 
 	for _, test := range vocabTitles {
 		sent := tc.Convert(test.Input)