Refactor "string truncate" (#32984)

modules/util/truncate_test.go

@@ -4,43 +4,94 @@
 package util
 
 import (
+	"fmt"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 )
 
-func TestSplitString(t *testing.T) {
-	type testCase struct {
-		input    string
-		n        int
-		leftSub  string
-		ellipsis string
+func TestEllipsisString(t *testing.T) {
+	cases := []struct {
+		limit int
+
+		input, left, right string
+	}{
+		{limit: 0, input: "abcde", left: "", right: "…abcde"},
+		{limit: 1, input: "abcde", left: "", right: "…abcde"},
+		{limit: 2, input: "abcde", left: "", right: "…abcde"},
+		{limit: 3, input: "abcde", left: "…", right: "…abcde"},
+		{limit: 4, input: "abcde", left: "a…", right: "…bcde"},
+		{limit: 5, input: "abcde", left: "abcde", right: ""},
+		{limit: 6, input: "abcde", left: "abcde", right: ""},
+		{limit: 7, input: "abcde", left: "abcde", right: ""},
+
+		// a CJK char or emoji is considered as 2-ASCII width, the ellipsis is 3-ASCII width
+		{limit: 0, input: "测试文本", left: "", right: "…测试文本"},
+		{limit: 1, input: "测试文本", left: "", right: "…测试文本"},
+		{limit: 2, input: "测试文本", left: "", right: "…测试文本"},
+		{limit: 3, input: "测试文本", left: "…", right: "…测试文本"},
+		{limit: 4, input: "测试文本", left: "…", right: "…测试文本"},
+		{limit: 5, input: "测试文本", left: "测…", right: "…试文本"},
+		{limit: 6, input: "测试文本", left: "测…", right: "…试文本"},
+		{limit: 7, input: "测试文本", left: "测试…", right: "…文本"},
+		{limit: 8, input: "测试文本", left: "测试文本", right: ""},
+		{limit: 9, input: "测试文本", left: "测试文本", right: ""},
+	}
+	for _, c := range cases {
+		t.Run(fmt.Sprintf("%s(%d)", c.input, c.limit), func(t *testing.T) {
+			left, right := EllipsisDisplayStringX(c.input, c.limit)
+			assert.Equal(t, c.left, left, "left")
+			assert.Equal(t, c.right, right, "right")
+		})
 	}
 
-	test := func(tc []*testCase, f func(input string, n int) (left, right string)) {
-		for _, c := range tc {
-			l, r := f(c.input, c.n)
-			if c.ellipsis != "" {
-				assert.Equal(t, c.leftSub+c.ellipsis, l, "test split %q at %d, expected leftSub: %q", c.input, c.n, c.leftSub)
-				assert.Equal(t, c.ellipsis+c.input[len(c.leftSub):], r, "test split %s at %d, expected rightSub: %q", c.input, c.n, c.input[len(c.leftSub):])
-			} else {
-				assert.Equal(t, c.leftSub, l, "test split %q at %d, expected leftSub: %q", c.input, c.n, c.leftSub)
-				assert.Empty(t, r, "test split %q at %d, expected rightSub: %q", c.input, c.n, "")
-			}
+	t.Run("LongInput", func(t *testing.T) {
+		left, right := EllipsisDisplayStringX(strings.Repeat("abc", 240), 90)
+		assert.Equal(t, strings.Repeat("abc", 29)+"…", left)
+		assert.Equal(t, "…"+strings.Repeat("abc", 211), right)
+	})
+
+	t.Run("InvalidUtf8", func(t *testing.T) {
+		invalidCases := []struct {
+			limit       int
+			left, right string
+		}{
+			{limit: 0, left: "", right: "...\xef\x03\xfe\xef\x03\xfe"},
+			{limit: 1, left: "", right: "...\xef\x03\xfe\xef\x03\xfe"},
+			{limit: 2, left: "", right: "...\xef\x03\xfe\xef\x03\xfe"},
+			{limit: 3, left: "...", right: "...\xef\x03\xfe\xef\x03\xfe"},
+			{limit: 4, left: "...", right: "...\xef\x03\xfe\xef\x03\xfe"},
+			{limit: 5, left: "\xef\x03\xfe...", right: "...\xef\x03\xfe"},
+			{limit: 6, left: "\xef\x03\xfe\xef\x03\xfe", right: ""},
+			{limit: 7, left: "\xef\x03\xfe\xef\x03\xfe", right: ""},
 		}
-	}
+		for _, c := range invalidCases {
+			t.Run(fmt.Sprintf("%d", c.limit), func(t *testing.T) {
+				left, right := EllipsisDisplayStringX("\xef\x03\xfe\xef\x03\xfe", c.limit)
+				assert.Equal(t, c.left, left, "left")
+				assert.Equal(t, c.right, right, "right")
+			})
+		}
+	})
 
-	tc := []*testCase{
-		{"abc123xyz", 0, "", utf8Ellipsis},
-		{"abc123xyz", 1, "", utf8Ellipsis},
-		{"abc123xyz", 4, "a", utf8Ellipsis},
-		{"啊bc123xyz", 4, "", utf8Ellipsis},
-		{"啊bc123xyz", 6, "啊", utf8Ellipsis},
-		{"啊bc", 5, "啊bc", ""},
-		{"啊bc", 6, "啊bc", ""},
-		{"abc\xef\x03\xfe", 3, "", asciiEllipsis},
-		{"abc\xef\x03\xfe", 4, "a", asciiEllipsis},
-		{"\xef\x03", 1, "\xef\x03", ""},
-	}
-	test(tc, SplitStringAtByteN)
+	t.Run("IsLikelyEllipsisLeftPart", func(t *testing.T) {
+		assert.True(t, IsLikelyEllipsisLeftPart("abcde…"))
+		assert.True(t, IsLikelyEllipsisLeftPart("abcde..."))
+	})
+}
+
+func TestTruncateRunes(t *testing.T) {
+	assert.Equal(t, "", TruncateRunes("", 0))
+	assert.Equal(t, "", TruncateRunes("", 1))
+
+	assert.Equal(t, "", TruncateRunes("ab", 0))
+	assert.Equal(t, "a", TruncateRunes("ab", 1))
+	assert.Equal(t, "ab", TruncateRunes("ab", 2))
+	assert.Equal(t, "ab", TruncateRunes("ab", 3))
+
+	assert.Equal(t, "", TruncateRunes("测试", 0))
+	assert.Equal(t, "测", TruncateRunes("测试", 1))
+	assert.Equal(t, "测试", TruncateRunes("测试", 2))
+	assert.Equal(t, "测试", TruncateRunes("测试", 3))
 }