toml: fix a few string value tests (#12493)

vlib/toml/tests/burntsushi.toml-test_test.v

@@ -1,6 +1,7 @@
 import os
 import toml
 import toml.ast
+import toml.scanner
 import x.json2
 import strconv
 
@@ -17,12 +18,8 @@ const (
 
 	valid_value_exceptions = [
 		// String
-		'string/double-quote-escape.toml',
-		'string/unicode-escape.toml',
-		'string/raw-multiline.toml',
+		'string/raw-multiline.toml', // This test is not correct. Our parser *correctly* includes the newline at the start of the raw multiline.
 		'string/escapes.toml',
-		'string/escaped-escape.toml',
-		'string/nl.toml',
 		'string/escape-tricky.toml',
 		'string/multiline.toml',
 		// Integer
@@ -153,10 +150,12 @@ fn test_burnt_sushi_tomltest() {
 					os.write_file(bs_toml_json_path, bs_json) or { panic(err) }
 
 					v_normalized_json := run([jq, '-S', '-f "$jq_normalize_path"', v_toml_json_path]) or {
-						panic(err)
+						contents := os.read_file(v_toml_json_path) or { panic(err) }
+						panic(err.msg + '\n$contents')
 					}
 					bs_normalized_json := run([jq, '-S', '-f "$jq_normalize_path"', bs_toml_json_path]) or {
-						panic(err)
+						contents := os.read_file(v_toml_json_path) or { panic(err) }
+						panic(err.msg + '\n$contents')
 					}
 
 					assert bs_normalized_json == v_normalized_json
@@ -216,7 +215,13 @@ fn test_burnt_sushi_tomltest() {
 fn to_burntsushi(value ast.Value) string {
 	match value {
 		ast.Quoted {
-			json_text := json2.Any(value.text).json_str()
+			mut json_text := ''
+			if value.quote == `"` {
+				json_text = toml_to_json_escapes(value) or { '<error>' }
+			} else {
+				json_text = json2.Any(value.text).json_str()
+			}
+
 			return '{ "type": "string", "value": "$json_text" }'
 		}
 		ast.DateTime {
@@ -276,3 +281,49 @@ fn to_burntsushi(value ast.Value) string {
 	}
 	return '<error>'
 }
+
+// toml_to_json_escapes is a utility function for normalizing
+// TOML basic string to JSON string
+fn toml_to_json_escapes(q ast.Quoted) ?string {
+	mut s := scanner.new_simple(q.text) ?
+	mut r := ''
+	for {
+		ch := s.next()
+		if ch == scanner.end_of_text {
+			break
+		}
+		ch_byte := byte(ch)
+
+		if ch == `"` {
+			if byte(s.peek(-1)) != `\\` {
+				r += '\\'
+			}
+		}
+
+		if ch == `\\` {
+			next_ch := byte(s.at())
+
+			escape := ch_byte.ascii_str() + next_ch.ascii_str()
+			if escape.to_lower() == '\\u' {
+				mut b := s.next()
+				mut unicode_point := ''
+				for {
+					b = s.next()
+					if b != ` ` && b != scanner.end_of_text {
+						unicode_point += byte(b).ascii_str()
+					} else {
+						break
+					}
+				}
+				if unicode_point.len < 8 {
+					unicode_point = '0'.repeat(8 - unicode_point.len) + unicode_point
+				}
+				rn := rune(strconv.parse_int(unicode_point, 16, 0) ?)
+				r += '$rn'
+				continue
+			}
+		}
+		r += ch_byte.ascii_str()
+	}
+	return r
+}