pkg/util: Move the wcwidth utilities to a new package, and add more tests.

This addresses #944.

pkg/cli/codearea_render.go

@@ -3,7 +3,7 @@ package cli
 import (
 	"github.com/elves/elvish/pkg/cli/term"
 	"github.com/elves/elvish/pkg/ui"
-	"github.com/elves/elvish/pkg/util"
+	"github.com/elves/elvish/pkg/wcwidth"
 )
 
 // View model, calculated from State and used for rendering.
@@ -112,7 +112,7 @@ func truncateToHeight(b *term.Buffer, maxHeight int) {
 func styledWcswidth(t ui.Text) int {
 	w := 0
 	for _, seg := range t {
-		w += util.Wcswidth(seg.Text)
+		w += wcwidth.Of(seg.Text)
 	}
 	return w
 }

pkg/cli/listbox_window.go

@@ -1,6 +1,6 @@
 package cli
 
-import "github.com/elves/elvish/pkg/util"
+import "github.com/elves/elvish/pkg/wcwidth"
 
 // The number of lines the listing mode keeps between the current selected item
 // and the top and bottom edges of the window, unless the available height is
@@ -133,7 +133,7 @@ func maxWidth(items Items, padding, low, high int) int {
 	for i := low; i < high && i < n; i++ {
 		w := 0
 		for _, seg := range items.Show(i) {
-			w += util.Wcswidth(seg.Text)
+			w += wcwidth.Of(seg.Text)
 		}
 		if width < w {
 			width = w

pkg/cli/term/buffer.go

@@ -4,7 +4,7 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/elves/elvish/pkg/util"
+	"github.com/elves/elvish/pkg/wcwidth"
 )
 
 // Cell is an indivisible unit on the screen. It is not necessarily 1 column
@@ -23,7 +23,7 @@ type Pos struct {
 func CellsWidth(cs []Cell) int {
 	w := 0
 	for _, c := range cs {
-		w += util.Wcswidth(c.Text)
+		w += wcwidth.Of(c.Text)
 	}
 	return w
 }
@@ -171,7 +171,7 @@ func (b *Buffer) TTYString() string {
 				lastStyle = cell.Style
 			}
 			sb.WriteString(cell.Text)
-			usedWidth += util.Wcswidth(cell.Text)
+			usedWidth += wcwidth.Of(cell.Text)
 		}
 		if lastStyle != "" {
 			sb.WriteString("\033[m")

pkg/cli/term/buffer_builder.go

@@ -4,7 +4,7 @@ import (
 	"strings"
 
 	"github.com/elves/elvish/pkg/ui"
-	"github.com/elves/elvish/pkg/util"
+	"github.com/elves/elvish/pkg/wcwidth"
 )
 
 // BufferBuilder supports building of Buffer.
@@ -68,7 +68,7 @@ func (bb *BufferBuilder) appendLine() {
 func (bb *BufferBuilder) appendCell(c Cell) {
 	n := len(bb.Lines)
 	bb.Lines[n-1] = append(bb.Lines[n-1], c)
-	bb.Col += util.Wcswidth(c.Text)
+	bb.Col += wcwidth.Of(c.Text)
 }
 
 // Newline starts a newline.
@@ -104,7 +104,7 @@ func (bb *BufferBuilder) WriteRuneSGR(r rune, style string) *BufferBuilder {
 		c = Cell{"^" + string(r^0x40), style}
 	}
 
-	if bb.Col+util.Wcswidth(c.Text) > bb.Width {
+	if bb.Col+wcwidth.Of(c.Text) > bb.Width {
 		bb.Newline()
 		bb.appendCell(c)
 	} else {

pkg/cli/term/setup.go

@@ -5,7 +5,7 @@ import (
 	"os"
 
 	"github.com/elves/elvish/pkg/sys"
-	"github.com/elves/elvish/pkg/util"
+	"github.com/elves/elvish/pkg/wcwidth"
 )
 
 // Setup sets up the terminal so that it is suitable for the Reader and
@@ -53,7 +53,7 @@ func setupVT(out *os.File) error {
 		   LackEOL character. Otherwise, we are now in the next line and this is
 		   a no-op. The LackEOL character remains.
 	*/
-	s += fmt.Sprintf("\033[?7h%s%*s\r \r", lackEOL, width-util.Wcwidth(lackEOLRune), "")
+	s += fmt.Sprintf("\033[?7h%s%*s\r \r", lackEOL, width-wcwidth.OfRune(lackEOLRune), "")
 
 	/*
 		Turn off autowrap.

pkg/cli/textview.go

@@ -5,7 +5,7 @@ import (
 
 	"github.com/elves/elvish/pkg/cli/term"
 	"github.com/elves/elvish/pkg/ui"
-	"github.com/elves/elvish/pkg/util"
+	"github.com/elves/elvish/pkg/wcwidth"
 )
 
 // TextView is a Widget for displaying text, with support for vertical
@@ -68,7 +68,7 @@ func (w *textView) Render(width, height int) *term.Buffer {
 		if i > first {
 			bb.Newline()
 		}
-		bb.Write(util.TrimWcwidth(lines[i], textWidth))
+		bb.Write(wcwidth.Trim(lines[i], textWidth))
 	}
 	buf := bb.Buffer()
 

pkg/diag/context.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/elves/elvish/pkg/util"
+	"github.com/elves/elvish/pkg/wcwidth"
 )
 
 // Context is a range of text in a source code. It is typically used for
@@ -92,7 +92,7 @@ func (c *Context) ShowCompact(sourceIndent string) string {
 	}
 	desc := c.Name + ", " + c.lineRange() + " "
 	// Extra indent so that following lines line up with the first line.
-	descIndent := strings.Repeat(" ", util.Wcswidth(desc))
+	descIndent := strings.Repeat(" ", wcwidth.Of(desc))
 	return desc + c.relevantSource(sourceIndent+descIndent)
 }
 

pkg/edit/builtins.go

@@ -14,6 +14,7 @@ import (
 	"github.com/elves/elvish/pkg/parse/parseutil"
 	"github.com/elves/elvish/pkg/ui"
 	"github.com/elves/elvish/pkg/util"
+	"github.com/elves/elvish/pkg/wcwidth"
 )
 
 //elvdoc:fn binding-table
@@ -333,8 +334,8 @@ func moveDotUp(buffer string, dot int) int {
 	}
 	prevEOL := sol - 1
 	prevSOL := util.FindLastSOL(buffer[:prevEOL])
-	width := util.Wcswidth(buffer[sol:dot])
-	return prevSOL + len(util.TrimWcwidth(buffer[prevSOL:prevEOL], width))
+	width := wcwidth.Of(buffer[sol:dot])
+	return prevSOL + len(wcwidth.Trim(buffer[prevSOL:prevEOL], width))
 }
 
 //elvdoc:fn move-dot-down
@@ -351,8 +352,8 @@ func moveDotDown(buffer string, dot int) int {
 	nextSOL := eol + 1
 	nextEOL := util.FindFirstEOL(buffer[nextSOL:]) + nextSOL
 	sol := util.FindLastSOL(buffer[:dot])
-	width := util.Wcswidth(buffer[sol:dot])
-	return nextSOL + len(util.TrimWcwidth(buffer[nextSOL:nextEOL], width))
+	width := wcwidth.Of(buffer[sol:dot])
+	return nextSOL + len(wcwidth.Trim(buffer[nextSOL:nextEOL], width))
 }
 
 // TODO(xiaq): Document the concepts of words, small words and alnum words.

pkg/eval/builtin_fn_str.go

@@ -10,7 +10,7 @@ import (
 	"unicode/utf8"
 
 	"github.com/elves/elvish/pkg/eval/vals"
-	"github.com/elves/elvish/pkg/util"
+	"github.com/elves/elvish/pkg/wcwidth"
 )
 
 // String operations.
@@ -260,8 +260,8 @@ func init() {
 		"chr":  chr,
 		"base": base,
 
-		"wcswidth":          util.Wcswidth,
-		"-override-wcwidth": util.OverrideWcwidth,
+		"wcswidth":          wcwidth.Of,
+		"-override-wcwidth": wcwidth.Override,
 
 		"has-prefix": strings.HasPrefix,
 		"has-suffix": strings.HasSuffix,

pkg/ui/text.go

@@ -6,7 +6,7 @@ import (
 	"strconv"
 
 	"github.com/elves/elvish/pkg/eval/vals"
-	"github.com/elves/elvish/pkg/util"
+	"github.com/elves/elvish/pkg/wcwidth"
 )
 
 // Text contains of a list of styled Segments.
@@ -177,10 +177,10 @@ func (t Text) SplitByRune(r rune) []Text {
 func (t Text) TrimWcwidth(wmax int) Text {
 	var newt Text
 	for _, seg := range t {
-		w := util.Wcswidth(seg.Text)
+		w := wcwidth.Of(seg.Text)
 		if w >= wmax {
 			newt = append(newt,
-				&Segment{seg.Style, util.TrimWcwidth(seg.Text, wmax)})
+				&Segment{seg.Style, wcwidth.Trim(seg.Text, wmax)})
 			break
 		}
 		wmax -= w

pkg/util/wcwidth_test.go

@@ -1,76 +0,0 @@
-package util
-
-import (
-	"testing"
-)
-
-var wcwidthTests = []struct {
-	in     rune
-	wanted int
-}{
-	{'\u0301', 0}, // Combining acute accent
-	{'a', 1},
-	{'Ω', 1},
-	{'好', 2},
-	{'か', 2},
-}
-
-func TestWcwidth(t *testing.T) {
-	for _, tt := range wcwidthTests {
-		out := Wcwidth(tt.in)
-		if out != tt.wanted {
-			t.Errorf("wcwidth(%q) => %v, want %v", tt.in, out, tt.wanted)
-		}
-	}
-}
-
-func TestOverrideWcwidth(t *testing.T) {
-	r := '❱'
-	oldw := Wcwidth(r)
-	w := oldw + 1
-
-	OverrideWcwidth(r, w)
-	if Wcwidth(r) != w {
-		t.Errorf("Wcwidth(%q) != %d after OverrideWcwidth", r, w)
-	}
-	UnoverrideWcwidth(r)
-	if Wcwidth(r) != oldw {
-		t.Errorf("Wcwidth(%q) != %d after UnoverrideWcwidth", r, oldw)
-	}
-}
-
-func TestTrimWcwidth(t *testing.T) {
-	if TrimWcwidth("abc", 2) != "ab" {
-		t.Errorf("TrimWcwidth #1 fails")
-	}
-	if TrimWcwidth("你好", 3) != "你" {
-		t.Errorf("TrimWcwidth #2 fails")
-	}
-}
-
-func TestForceWcwidth(t *testing.T) {
-	for i, c := range []struct {
-		s    string
-		w    int
-		want string
-	}{
-		// Triming
-		{"abc", 2, "ab"},
-		{"你好", 2, "你"},
-		// Padding
-		{"abc", 4, "abc "},
-		{"你好", 5, "你好 "},
-		// Trimming and Padding
-		{"你好", 3, "你 "},
-	} {
-		if got := ForceWcwidth(c.s, c.w); got != c.want {
-			t.Errorf("ForceWcwidth #%d fails", i)
-		}
-	}
-}
-
-func TestTrimEachLineWcwidth(t *testing.T) {
-	if TrimEachLineWcwidth("abcdefg\n你好", 3) != "abc\n你" {
-		t.Errorf("TestTrimEachLineWcwidth fails")
-	}
-}

pkg/wcwidth/wcwidth.go

@@ -1,4 +1,6 @@
-package util
+// Package wcwidth provides utilities for determining the column width of
+// characters when displayed on the terminal.
+package wcwidth
 
 import (
 	"sort"
@@ -65,8 +67,8 @@ func isCombining(r rune) bool {
 	return i < n && r >= combining[i][0]
 }
 
-// Wcwidth returns the width of a rune when displayed on the terminal.
-func Wcwidth(r rune) int {
+// OfRune returns the column width of a rune.
+func OfRune(r rune) int {
 	if w, ok := wcwidthOverride[r]; ok {
 		return w
 	}
@@ -95,34 +97,33 @@ func Wcwidth(r rune) int {
 	return 1
 }
 
-// OverrideWcwidth overrides the wcwidth of a rune to be a specific non-negative
-// value. OverrideWcwidth panics if w < 0.
-func OverrideWcwidth(r rune, w int) {
+// Override overrides the column width of a rune to be a specific non-negative
+// value. It panics if w < 0.
+func Override(r rune, w int) {
 	if w < 0 {
 		panic("negative width")
 	}
 	wcwidthOverride[r] = w
 }
 
-// UnoverrideWcwidth removes the override of a rune.
-func UnoverrideWcwidth(r rune) {
+// Unoverride removes the column width override of a rune.
+func Unoverride(r rune) {
 	delete(wcwidthOverride, r)
 }
 
-// Wcswidth returns the width of a string when displayed on the terminal,
-// assuming no soft line breaks.
-func Wcswidth(s string) (w int) {
+// Of returns the column width of a string, assuming no soft line breaks.
+func Of(s string) (w int) {
 	for _, r := range s {
-		w += Wcwidth(r)
+		w += OfRune(r)
 	}
 	return
 }
 
-// TrimWcwidth trims the string s so that it has a width of at most wmax.
-func TrimWcwidth(s string, wmax int) string {
+// Trim trims the string s so that it has a column width of at most wmax.
+func Trim(s string, wmax int) string {
 	w := 0
 	for i, r := range s {
-		w += Wcwidth(r)
+		w += OfRune(r)
 		if w > wmax {
 			return s[:i]
 		}
@@ -130,12 +131,11 @@ func TrimWcwidth(s string, wmax int) string {
 	return s
 }
 
-// ForceWcwidth forces the string s to the given display width by trimming and
-// padding.
-func ForceWcwidth(s string, width int) string {
+// Force forces the string s to the given column width by trimming and padding.
+func Force(s string, width int) string {
 	w := 0
 	for i, r := range s {
-		w0 := Wcwidth(r)
+		w0 := OfRune(r)
 		w += w0
 		if w > width {
 			w -= w0
@@ -146,12 +146,12 @@ func ForceWcwidth(s string, width int) string {
 	return s + strings.Repeat(" ", width-w)
 }
 
-// TrimEachLineWcwidth trims each line of s so that it is no wider than the
-// specified width.
-func TrimEachLineWcwidth(s string, width int) string {
+// TrimEachLine trims each line of s so that it is no wider than the specified
+// width.
+func TrimEachLine(s string, width int) string {
 	lines := strings.Split(s, "\n")
 	for i := range lines {
-		lines[i] = TrimWcwidth(lines[i], width)
+		lines[i] = Trim(lines[i], width)
 	}
 	return strings.Join(lines, "\n")
 }

pkg/wcwidth/wcwidth_test.go

@@ -0,0 +1,71 @@
+package wcwidth
+
+import (
+	"testing"
+
+	"github.com/elves/elvish/pkg/tt"
+)
+
+var Args = tt.Args
+
+func TestOf(t *testing.T) {
+	tt.Test(t, tt.Fn("Of", Of), tt.Table{
+		Args("\u0301").Rets(0), // Combining acute accent
+		Args("a").Rets(1),
+		Args("Ω").Rets(1),
+		Args("好").Rets(2),
+		Args("か").Rets(2),
+
+		Args("abc").Rets(3),
+		Args("你好").Rets(4),
+	})
+}
+
+func TestOverride(t *testing.T) {
+	r := '❱'
+	oldw := OfRune(r)
+	w := oldw + 1
+
+	Override(r, w)
+	if OfRune(r) != w {
+		t.Errorf("Wcwidth(%q) != %d after OverrideWcwidth", r, w)
+	}
+	Unoverride(r)
+	if OfRune(r) != oldw {
+		t.Errorf("Wcwidth(%q) != %d after UnoverrideWcwidth", r, oldw)
+	}
+}
+
+func TestTrim(t *testing.T) {
+	tt.Test(t, tt.Fn("Trim", Trim), tt.Table{
+		Args("abc", 1).Rets("a"),
+		Args("abc", 2).Rets("ab"),
+		Args("abc", 3).Rets("abc"),
+		Args("abc", 4).Rets("abc"),
+
+		Args("你好", 1).Rets(""),
+		Args("你好", 2).Rets("你"),
+		Args("你好", 3).Rets("你"),
+		Args("你好", 4).Rets("你好"),
+		Args("你好", 5).Rets("你好"),
+	})
+}
+
+func TestForce(t *testing.T) {
+	tt.Test(t, tt.Fn("Force", Force), tt.Table{
+		// Triming
+		Args("abc", 2).Rets("ab"),
+		Args("你好", 2).Rets("你"),
+		// Padding
+		Args("abc", 4).Rets("abc "),
+		Args("你好", 5).Rets("你好 "),
+		// Trimming and Padding
+		Args("你好", 3).Rets("你 "),
+	})
+}
+
+func TestTrimEachLine(t *testing.T) {
+	tt.Test(t, tt.Fn("TrimEachLine", TrimEachLine), tt.Table{
+		Args("abcdefg\n你好", 3).Rets("abc\n你"),
+	})
+}