milestone 21: abp list exceptions and a regex rule kind

tests/fuzz/compiler_fuzz.zig

@@ -94,6 +94,8 @@ fn compileOnce(
     var list_w: std.Io.Writer.Discarding = .init(&list_sink);
     var wild_sink: [0]u8 = .{};
     var wild_w: std.Io.Writer.Discarding = .init(&wild_sink);
+    var allow_sink: [0]u8 = .{};
+    var allow_w: std.Io.Writer.Discarding = .init(&allow_sink);
 
     return compiler.compile(
         std.testing.allocator,
@@ -101,6 +103,7 @@ fn compileOnce(
         format,
         &list_w.writer,
         &wild_w.writer,
+        &allow_w.writer,
     ) catch |err| switch (err) {
         error.OutOfMemory,
         error.TooManyDomains,
@@ -122,12 +125,13 @@ fn expectConsistent(counts: compiler.Counts, bytes: []const u8) !void {
     // A candidate is a non-empty whitespace-separated field or a whole wildcard
     // line, so every candidate consumes at least one byte of the input, and a
     // written name is a candidate that survived.
-    const candidates = @as(u64, counts.domains) + counts.wildcards +
+    const candidates = @as(u64, counts.domains) + counts.wildcards + counts.exceptions +
         counts.duplicates + counts.invalid;
     try std.testing.expect(candidates <= bytes.len + 1);
 
     try std.testing.expect(counts.domains <= compiler.max_domains);
     try std.testing.expect(counts.wildcards <= compiler.max_domains);
+    try std.testing.expect(counts.exceptions <= compiler.max_domains);
 }
 
 // ---------------------------------------------------------------------------
@@ -154,6 +158,9 @@ const corpus = [_][]const u8{
     sliceInput(long_line_terminated),
     sliceInput("# a hosts list\n0.0.0.0 ads.example.com # advertising\n"),
     sliceInput("||ads.example.net^\n@@||allow.example.net^\n/re[0-9]+/\n"),
+    // The three exception shapes: the two accepted spellings with the one
+    // tolerated modifier, and a form that stays unsupported.
+    sliceInput("@@||a.example.net^$important\n@@||b.example.net\n@@c.example.net\n"),
     sliceInput("*.wild.example.org\nlocalhost\nAdS.Example.COM.\n"),
 };