scanner: replace ascii unicode(\u0020) with hex(\x20) (#9259)

vlib/v/scanner/scanner.v

@@ -1101,6 +1101,7 @@ fn (mut s Scanner) ident_string() string {
 		start++
 	}
 	s.is_inside_string = false
+	mut u_to_x_pos := []int{} // pos list to replace \u0020 -> \x20
 	slash := `\\`
 	for {
 		s.pos++
@@ -1146,13 +1147,17 @@ fn (mut s Scanner) ident_string() string {
 				s.error(r'`\x` used with no following hex digits')
 			}
 			// Escape `\u`
-			if c == `u` && (s.text[s.pos + 1] == s.quote
-				|| s.text[s.pos + 2] == s.quote || s.text[s.pos + 3] == s.quote
-				|| s.text[s.pos + 4] == s.quote || !s.text[s.pos + 1].is_hex_digit()
-				|| !s.text[s.pos + 2].is_hex_digit()
-				|| !s.text[s.pos + 3].is_hex_digit()
-				|| !s.text[s.pos + 4].is_hex_digit()) {
+			if c == `u` {
+				if s.text[s.pos + 1] == s.quote || s.text[s.pos + 2] == s.quote
+					|| s.text[s.pos + 3] == s.quote || s.text[s.pos + 4] == s.quote
+					|| !s.text[s.pos + 1].is_hex_digit() || !s.text[s.pos + 2].is_hex_digit()
+					|| !s.text[s.pos + 3].is_hex_digit() || !s.text[s.pos + 4].is_hex_digit() {
 					s.error(r'`\u` incomplete unicode character value')
+				} else if s.text[s.pos + 1] == `0` && s.text[s.pos + 2] == `0`
+					&& (`0` <= s.text[s.pos + 3] && s.text[s.pos + 3] < `8`) {
+					// ascii
+					u_to_x_pos << s.pos - 1
+				}
 			}
 		}
 		// ${var} (ignore in vfmt mode) (skip \$)
@@ -1179,6 +1184,15 @@ fn (mut s Scanner) ident_string() string {
 	}
 	if start <= s.pos {
 		mut string_so_far := s.text[start..end]
+		if u_to_x_pos.len > 0 {
+			mut ss := []string{cap: u_to_x_pos.len + 1}
+			ss << string_so_far[..u_to_x_pos[0] - start]
+			for i in 0 .. u_to_x_pos.len - 1 {
+				ss << r'\x' + string_so_far[u_to_x_pos[i] - start + 4..u_to_x_pos[i + 1] - start]
+			}
+			ss << r'\x' + string_so_far[u_to_x_pos.last() + 4 - start..]
+			string_so_far = ss.join('')
+		}
 		if n_cr_chars > 0 {
 			string_so_far = string_so_far.replace('\r', '')
 		}

vlib/v/tests/strings_unicode_test.v

@@ -0,0 +1,10 @@
+fn test_raw_string() {
+	assert r'\n\u00c0' == '\\n\\u00c0'
+}
+
+fn test_escape() {
+	assert '\x20' == ' '
+	assert '\u0020' == ' '
+	// assert '\u00c4' == 'Ä'
+	assert '\r\n'.bytes() == [byte(0x0d), 0x0a]
+}