Fix radix string round trips with literal separators

CHANGELOG.md

@@ -1,3 +1,7 @@
+## Next Release
+
+- Fixed `LogicValue.ofRadixString` round trips with empty separators and separators containing regular-expression metacharacters (<https://github.com/intel/rohd/issues/722>).
+
 ## 0.6.11
 
 - Added `NetlistSynthesizer` for generating JSON netlists, with configurable synthesis passes, validation, and hierarchy support (<https://github.com/intel/rohd/pull/675>).

lib/src/values/logic_value.dart

@@ -763,7 +763,10 @@ abstract class LogicValue implements Comparable<LogicValue> {
   /// illegal characters
   /// in the string or too long of a value string.
   ///
-  ///  Strings created by [toRadixString] are parsed by [ofRadixString].
+  /// Strings created by [toRadixString] are parsed by [ofRadixString].
+  /// [sepChar] is interpreted literally and must match the separator used when
+  /// formatting the string. An empty [sepChar] is allowed for strings without
+  /// separators.
   ///
   /// If the LogicValue width is not encoded as round number of radix
   /// characters, the leading character must be small enough to be encoded
@@ -773,12 +776,13 @@ abstract class LogicValue implements Comparable<LogicValue> {
   ///  - 11'h4aa
   ///  - 12'haa
   static LogicValue ofRadixString(String valueString, {String sepChar = '_'}) {
-    if (radixStringChars.contains(sepChar)) {
+    if (sepChar.isNotEmpty && radixStringChars.contains(sepChar)) {
       throw LogicValueConstructionException('separation character invalid');
     }
+    final escapedSeparator = RegExp.escape(sepChar);
     if (RegExp(r'^\d+').firstMatch(valueString) != null) {
       final formatStr =
-          RegExp("^(\\d+)'([bqodh])([0-9aAbBcCdDeEfFzZxX<>$sepChar]*)")
+          RegExp("^(\\d+)'([bqodh])([0-9aAbBcCdDeEfFzZxX<>$escapedSeparator]*)")
               .firstMatch(valueString);
       if (formatStr != null) {
         if (valueString.length != formatStr.group(0)!.length) {

test/logic_value_test.dart

@@ -2144,6 +2144,21 @@ void main() {
       }
     });
 
+    for (final separator in ['', ']', r'\', '[', '^', '.', '-']) {
+      test('radixString literal separator "$separator" round trip', () {
+        final known = LogicValue.ofInt(0x1234abcd, 40);
+        final fourState = LogicValue.ofString('10xz1010zz01');
+        for (final radix in [2, 4, 8, 10, 16]) {
+          for (final value in [known, if (radix != 10) fourState]) {
+            final encoded = value.toRadixString(
+                radix: radix, leadingZeros: true, sepChar: separator);
+            expect(
+                LogicValue.ofRadixString(encoded, sepChar: separator), value);
+          }
+        }
+      });
+    }
+
     test('radixString space separators', () {
       final lv = LogicValue.ofRadixString("10'b10 0010 0111", sepChar: ' ');
       expect(lv.toInt(), equals(551));