feat: convert tabs to spaces with Style.TabWidth(int) (#204)

* feat: convert tabs to spaces with Style.TabWidth(int)

By default tabs will be converted to 4 spaces. To disable tab
conversion set Style.TabWidth(NoTabConversion).

get.go

@@ -370,6 +370,12 @@ func (s Style) GetMaxHeight() int {
 	return s.getAsInt(maxHeightKey)
 }
 
+// GetTabWidth returns the style's tab width setting. If no value is set 4 is
+// returned which is the implicit default.
+func (s Style) GetTabWidth() int {
+	return s.getAsInt(tabWidthKey)
+}
+
 // GetUnderlineSpaces returns whether or not the style is set to underline
 // spaces. If not value is set false is returned.
 func (s Style) GetUnderlineSpaces() bool {

set.go

@@ -14,7 +14,14 @@ func (s *Style) set(key propKey, value interface{}) {
 
 	switch v := value.(type) {
 	case int:
-		// We don't allow negative integers on any of our values, so just keep
+		// TabWidth is the only property that may have a negative value (and
+		// that negative value can be no less than -1).
+		if key == tabWidthKey {
+			s.rules[key] = v
+			break
+		}
+
+		// We don't allow negative integers on any of our other values, so just keep
 		// them at zero or above. We could use uints instead, but the
 		// conversions are a little tedious, so we're sticking with ints for
 		// sake of usability.
@@ -497,13 +504,30 @@ func (s Style) MaxWidth(n int) Style {
 // styles.
 //
 // Because this in intended to be used at the time of render, this method will
-// not mutate the style and instead return a copy.
+// not mutate the style and instead returns a copy.
 func (s Style) MaxHeight(n int) Style {
 	o := s.Copy()
 	o.set(maxHeightKey, n)
 	return o
 }
 
+// NoTabConversion can be passed to [Style.TabWidth] to disable the replacement
+// of tabs with spaces at render time.
+const NoTabConversion = -1
+
+// TabWidth sets the number of spaces that a tab (/t) should be rendered as.
+// When set to 0, tabs will be removed. To disable the replacement of tabs with
+// spaces entirely, set this to [NoTabConversion].
+//
+// By default, tabs will be replaced with 4 spaces.
+func (s Style) TabWidth(n int) Style {
+	if n <= -1 {
+		n = -1
+	}
+	s.set(tabWidthKey, n)
+	return s
+}
+
 // UnderlineSpaces determines whether to underline spaces between words. By
 // default, this is true. Spaces can also be underlined without underlining the
 // text itself.

style.go

@@ -10,6 +10,8 @@ import (
 	"github.com/muesli/termenv"
 )
 
+const tabWidthDefault = 4
+
 // Property for a key.
 type propKey int
 
@@ -68,6 +70,7 @@ const (
 	inlineKey
 	maxWidthKey
 	maxHeightKey
+	tabWidthKey
 	underlineSpacesKey
 	strikethroughSpacesKey
 )
@@ -224,7 +227,7 @@ func (s Style) Render(strs ...string) string {
 	)
 
 	if len(s.rules) == 0 {
-		return str
+		return s.maybeConvertTabs(str)
 	}
 
 	// Enable support for ANSI on the legacy Windows cmd.exe console. This is a
@@ -287,6 +290,9 @@ func (s Style) Render(strs ...string) string {
 		teSpace = teSpace.CrossOut()
 	}
 
+	// Potentially convert tabs to spaces
+	str = s.maybeConvertTabs(str)
+
 	// Strip newlines in single line mode
 	if inline {
 		str = strings.ReplaceAll(str, "\n", "")
@@ -397,6 +403,21 @@ func (s Style) Render(strs ...string) string {
 	return str
 }
 
+func (s Style) maybeConvertTabs(str string) string {
+	tw := tabWidthDefault
+	if s.isSet(tabWidthKey) {
+		tw = s.getAsInt(tabWidthKey)
+	}
+	switch tw {
+	case -1:
+		return str
+	case 0:
+		return strings.ReplaceAll(str, "\t", "")
+	default:
+		return strings.ReplaceAll(str, "\t", strings.Repeat(" ", tw))
+	}
+}
+
 func (s Style) applyMargins(str string, inline bool) string {
 	var (
 		topMargin    = s.getAsInt(marginTopKey)

style_test.go

@@ -181,7 +181,8 @@ func TestStyleCopy(t *testing.T) {
 		Foreground(Color("#ffffff")).
 		Background(Color("#111111")).
 		Margin(1, 1, 1, 1).
-		Padding(1, 1, 1, 1)
+		Padding(1, 1, 1, 1).
+		TabWidth(2)
 
 	i := s.Copy()
 
@@ -202,6 +203,7 @@ func TestStyleCopy(t *testing.T) {
 	requireEqual(t, s.GetPaddingRight(), i.GetPaddingRight())
 	requireEqual(t, s.GetPaddingTop(), i.GetPaddingTop())
 	requireEqual(t, s.GetPaddingBottom(), i.GetPaddingBottom())
+	requireEqual(t, s.GetTabWidth(), i.GetTabWidth())
 }
 
 func TestStyleUnset(t *testing.T) {
@@ -312,6 +314,12 @@ func TestStyleUnset(t *testing.T) {
 	requireTrue(t, s.GetBorderLeft())
 	s.UnsetBorderLeft()
 	requireFalse(t, s.GetBorderLeft())
+
+	// tab width
+	s = NewStyle().TabWidth(2)
+	requireEqual(t, s.GetTabWidth(), 2)
+	s.UnsetTabWidth()
+	requireNotEqual(t, s.GetTabWidth(), 4)
 }
 
 func TestStyleValue(t *testing.T) {
@@ -352,7 +360,17 @@ func TestStyleValue(t *testing.T) {
 				res, formatEscapes(res))
 		}
 	}
+}
 
+func TestTabConversion(t *testing.T) {
+	s := NewStyle()
+	requireEqual(t, "[    ]", s.Render("[\t]"))
+	s = NewStyle().TabWidth(2)
+	requireEqual(t, "[  ]", s.Render("[\t]"))
+	s = NewStyle().TabWidth(0)
+	requireEqual(t, "[]", s.Render("[\t]"))
+	s = NewStyle().TabWidth(-1)
+	requireEqual(t, "[\t]", s.Render("[\t]"))
 }
 
 func BenchmarkStyleRender(b *testing.B) {

unset.go

@@ -287,6 +287,12 @@ func (s Style) UnsetMaxHeight() Style {
 	return s
 }
 
+// UnsetMaxHeight removes the max height style rule, if set.
+func (s Style) UnsetTabWidth() Style {
+	delete(s.rules, tabWidthKey)
+	return s
+}
+
 // UnsetUnderlineSpaces removes the value set by UnderlineSpaces.
 func (s Style) UnsetUnderlineSpaces() Style {
 	delete(s.rules, underlineSpacesKey)