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Fix reported range when an optional parser is lifted to an AST parser #48

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Oct 31, 2021
Merged

Fix reported range when an optional parser is lifted to an AST parser #48

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23 changes: 18 additions & 5 deletions src/commonMain/kotlin/com/github/h0tk3y/betterParse/st/LiftToSyntaxTree.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,9 @@ import com.github.h0tk3y.betterParse.grammar.Grammar
import com.github.h0tk3y.betterParse.grammar.ParserReference
import com.github.h0tk3y.betterParse.lexer.Token
import com.github.h0tk3y.betterParse.lexer.TokenMatch
import com.github.h0tk3y.betterParse.parser.EmptyParser
import com.github.h0tk3y.betterParse.parser.Parser
import com.github.h0tk3y.betterParse.lexer.TokenMatchesSequence
import com.github.h0tk3y.betterParse.parser.*
import com.github.h0tk3y.betterParse.parser.ParsedValue

/** Encloses custom logic for transforming a [Parser] to a parser of [SyntaxTree].
* A correct implementation overrides [liftToSyntaxTree] so that it calls `recurse` for the sub-parsers, if any, and
Expand Down Expand Up @@ -108,9 +109,21 @@ private class ParserToSyntaxTreeLifter(
}

private fun <T> liftOptionalCombinatorToAST(combinator: OptionalCombinator<T>): Parser<SyntaxTree<T?>> {
val optionalLifted = optional(lift(combinator.parser))
return optionalLifted.map {
SyntaxTree(it?.item, listOfNotNull(it), combinator, it?.range ?: 0..0)
return object: Parser<SyntaxTree<T?>> {
override fun tryParse(tokens: TokenMatchesSequence, fromPosition: Int): ParseResult<SyntaxTree<T?>> {
val result = optional(lift(combinator.parser)).tryParse(tokens, fromPosition)
return when (result) {
is ErrorResult -> result
is Parsed -> {
val inputPosition = tokens[fromPosition]?.offset ?: 0
val ast = SyntaxTree(result.value?.item,
listOfNotNull(result.value),
combinator,
result.value?.range ?: inputPosition..inputPosition)
ParsedValue(ast, result.nextPosition)
}
}
}
}
}

Expand Down