Basic headline

src/parser/parser_types.nim

@@ -166,6 +166,7 @@ proc applyParsersToSingle*[T](
   builder: Builder[T],
   parsers: seq[Parser -> ParserResult],
   tokenFoldFn: (seq[ParserToken], T) -> T,
+  optional = false,
   initT: T,
 ): BuilderResult[T] =
   # Apply the current parsing functions and convert to text tokens wrapped in ParserResult
@@ -178,15 +179,20 @@ proc applyParsersToSingle*[T](
   newParser
   .foldTokens(
     (err: ParserError) => BuilderResult[T].err((builder, "foo")),
-    (newTokens: seq[ParserToken]) => BuilderResult[T].ok(
-      builder.initBuilder(
-        newParser.unsafeGet(),
-        builder.tree
-        .last()
-        .orElse(just(initT))
-        .map((x: T) => @[tokenFoldFn(newTokens, x)])
-        .getOrElse(newSeq[T]())
-      )
+    (newTokens: seq[ParserToken]) => (
+      if optional and newTokens.len == 0:
+        BuilderResult[T].ok(builder)
+      else:
+        BuilderResult[T].ok(
+          builder.initBuilder(
+            newParser.unsafeGet(),
+            builder.tree
+            .last()
+            .orElse(just(initT))
+            .map((x: T) => @[tokenFoldFn(newTokens, x)])
+            .getOrElse(newSeq[T]())
+          )
+        )
     )
   )
 
@@ -196,10 +202,17 @@ proc applyParsersSeqToSingle*[T](
   xs: seq[tuple[
     parsers: seq[Parser -> ParserResult],
     tokenFoldFn: (seq[ParserToken], T) -> T,
+    ignoreEmpty: bool,
   ]],
 ): BuilderResult[T] =
     xs.foldl(
-      a.flatMap((builder: Builder[T]) => applyParsersToSingle(builder, b[0], b[1], initT)),
+      a.flatMap((builder: Builder[T]) => applyParsersToSingle(
+        builder,
+        b.parsers,
+        b.tokenFoldFn,
+        b.ignoreEmpty,
+        initT
+      )),
       builderResult
     )