toml: fix scanner escape collecting in literal strings (#12022)

.gitattributes

@@ -2,3 +2,4 @@
 *.vv linguist-language=V text=auto eol=lf
 *.bat text=auto eol=crlf
  Dockerfile.* linguist-language=Dockerfile
+*.toml text eol=lf

vlib/toml/scanner/scanner.v

@@ -484,6 +484,8 @@ fn (mut s Scanner) extract_multiline_string() ?string {
 fn (mut s Scanner) handle_escapes(quote byte, is_multiline bool) (string, int) {
 	c := s.at()
 	mut lit := c.ascii_str()
+	is_literal_string := quote == `'`
+	if !is_literal_string {
 		if s.peek(1) == `u` && byte(s.peek(2)).is_hex_digit() && byte(s.peek(3)).is_hex_digit()
 			&& byte(s.peek(4)).is_hex_digit() && byte(s.peek(5)).is_hex_digit() {
 			lit += s.text[s.pos + 1..s.pos + 6] //.ascii_str()
@@ -499,7 +501,16 @@ fn (mut s Scanner) handle_escapes(quote byte, is_multiline bool) (string, int) {
 			util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'gulp escaped `$lit`')
 			return lit, 1
 		}
+	}
+	if is_literal_string {
+		if s.peek(1) == quote {
+			util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'ignore escape `$lit${byte(s.peek(1)).ascii_str()}` in literal string')
+			return '', 0
+		}
+	}
+
 	lit += byte(s.peek(1)).ascii_str()
+	util.printdbg(@MOD + '.' + @STRUCT + '.' + @FN, 'gulp escaped `$lit`')
 	return lit, 1
 }
 

vlib/toml/tests/strings_test.v

@@ -65,3 +65,22 @@ fn test_multiline_strings() {
 	value = toml_doc.value('mismatch2')
 	assert value.string() == 'aaa' + '"""' + 'bbb'
 }
+
+fn test_literal_strings() {
+	toml_file :=
+		os.real_path(os.join_path(os.dir(@FILE), 'testdata', os.file_name(@FILE).all_before_last('.'))) +
+		'.toml'
+	toml_doc := toml.parse(toml_file) or { panic(err) }
+
+	assert toml_doc.value('lit1').string() == r'\' // '\'
+	assert toml_doc.value('lit2').string() == r'\\' // '\\'
+	assert toml_doc.value('lit3').string() == r'\tricky\' // '\tricky\'
+
+	// NOTE to Windows users: git is set to use Unix EOLs for all TOML files (*.toml) in the repo.
+	// See `.gitattributes` in the project root for the rule in action.
+	// These lines would look like this on Windows:
+	// assert toml_doc.value('ml_lit1').string() == '\r\n\\'
+	assert toml_doc.value('ml_lit1').string() == '\n\\'
+	assert toml_doc.value('ml_lit2').string() == '\\\n\\'
+	assert toml_doc.value('ml_lit3').string() == '\\\ntricky\\\n'
+}

vlib/toml/tests/testdata/strings_test.toml

@@ -13,3 +13,15 @@ two_space = """ ""two quotes"" """
 
 mismatch1 = """aaa'''bbb"""
 mismatch2 = '''aaa"""bbb'''
+
+lit1 = '\'
+lit2 = '\\'
+lit3 = '\tricky\'
+
+ml_lit1 = '''
+\'''
+ml_lit2 = '''\
+\'''
+ml_lit3 = '''\
+tricky\
+'''