Fix a panic in NotifyCreateIssueComment (caused by string truncation) (#17928)

* Fix a panic in NotifyCreateIssueComment (caused by string truncation)

* more unit tests

* refactor

* fix some edge cases

* use SplitStringAtByteN for comment content

1 files changed, 61 insertions, 0 deletions

diff --git a/modules/util/truncate_test.go b/modules/util/truncate_test.go
new file mode 100644
index 0000000000..e505a6ee4a
--- /dev/null
+++ b/modules/util/truncate_test.go
@@ -0,0 +1,61 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package util
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSplitString(t *testing.T) {
+	type testCase struct {
+		input    string
+		n        int
+		leftSub  string
+		ellipsis string
+	}
+
+	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.Equal(t, "", r, "test split %q at %d, expected rightSub: %q", c.input, c.n, "")
+			}
+		}
+	}
+
+	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)
+
+	tc = []*testCase{
+		{"abc123xyz", 0, "", utf8Ellipsis},
+		{"abc123xyz", 1, "", utf8Ellipsis},
+		{"abc123xyz", 4, "abc", utf8Ellipsis},
+		{"啊bc123xyz", 4, "啊bc", utf8Ellipsis},
+		{"啊bc123xyz", 6, "啊bc12", utf8Ellipsis},
+		{"啊bc", 3, "啊bc", ""},
+		{"啊bc", 4, "啊bc", ""},
+		{"abc\xef\x03\xfe", 3, "", asciiEllipsis},
+		{"abc\xef\x03\xfe", 4, "a", asciiEllipsis},
+		{"\xef\x03", 1, "\xef\x03", ""},
+	}
+	test(tc, SplitStringAtRuneN)
+}