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Negative lookahead when parsing keywords (#506)
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* Negative lookahead when parsing keywords

* Removed redundant .backtrack
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@milessabin
milessabin authored Nov 9, 2023
1 parent 982bf58 commit a233aa3
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Showing 2 changed files with 68 additions and 25 deletions.
49 changes: 25 additions & 24 deletions modules/core/src/main/scala/parser.scala
View file
Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,12 @@ import scala.util.matching.Regex

object GraphQLParser {

def keyword(s: String) = token(string(s))
val nameInitial = ('A' to 'Z') ++ ('a' to 'z') ++ Seq('_')
val nameSubsequent = nameInitial ++ ('0' to '9')

def keyword(s: String) = token(string(s) <* not(charIn(nameSubsequent)))

def punctuation(s: String) = token(string(s))

lazy val Document: Parser0[Ast.Document] =
(whitespace.void | comment).rep0 *> Definition.rep0 <* Parser.end
Expand Down Expand Up @@ -81,7 +86,7 @@ object GraphQLParser {
}

def directiveDefinition(desc: Option[Ast.Value.StringValue]): Parser[Ast.DirectiveDefinition] =
((keyword("directive") *> keyword("@") *> Name) ~
((keyword("directive") *> punctuation("@") *> Name) ~
ArgumentsDefinition.? ~ (keyword("repeatable").? <* keyword("on")) ~ DirectiveLocations).map {
case (((name, args), rpt), locs) => Ast.DirectiveDefinition(name, desc.map(_.value), args.getOrElse(Nil), rpt.isDefined, locs)
}
Expand Down Expand Up @@ -143,21 +148,21 @@ object GraphQLParser {
}

lazy val RootOperationTypeDefinition: Parser[Ast.RootOperationTypeDefinition] =
(OperationType ~ keyword(":") ~ NamedType ~ Directives).map {
(OperationType ~ punctuation(":") ~ NamedType ~ Directives).map {
case (((optpe, _), tpe), dirs) => Ast.RootOperationTypeDefinition(optpe, tpe, dirs)
}


lazy val Description = StringValue

lazy val ImplementsInterfaces =
(keyword("implements") ~ keyword("&").?) *> NamedType.repSep0(keyword("&"))
(keyword("implements") ~ punctuation("&").?) *> NamedType.repSep0(punctuation("&"))

lazy val FieldsDefinition: Parser[List[Ast.FieldDefinition]] =
braces(FieldDefinition.rep0)

lazy val FieldDefinition: Parser[Ast.FieldDefinition] =
(Description.?.with1 ~ Name ~ ArgumentsDefinition.? ~ keyword(":") ~ Type ~ Directives.?).map {
(Description.?.with1 ~ Name ~ ArgumentsDefinition.? ~ punctuation(":") ~ Type ~ Directives.?).map {
case (((((desc, name), args), _), tpe), dirs) => Ast.FieldDefinition(name, desc.map(_.value), args.getOrElse(Nil), tpe, dirs.getOrElse(Nil))
}

Expand All @@ -168,12 +173,12 @@ object GraphQLParser {
braces(InputValueDefinition.rep0)

lazy val InputValueDefinition: Parser[Ast.InputValueDefinition] =
(Description.?.with1 ~ (Name <* keyword(":")) ~ Type ~ DefaultValue.? ~ Directives.?).map {
(Description.?.with1 ~ (Name <* punctuation(":")) ~ Type ~ DefaultValue.? ~ Directives.?).map {
case ((((desc, name), tpe), dv), dirs) => Ast.InputValueDefinition(name, desc.map(_.value), tpe, dv, dirs.getOrElse(Nil))
}

lazy val UnionMemberTypes: Parser[List[Ast.Type.Named]] =
(keyword("=") *> keyword("|").?) *> NamedType.repSep0(keyword("|"))
(punctuation("=") *> punctuation("|").?) *> NamedType.repSep0(punctuation("|"))

lazy val EnumValuesDefinition: Parser[List[Ast.EnumValueDefinition]] =
braces(EnumValueDefinition.rep0)
Expand All @@ -184,7 +189,7 @@ object GraphQLParser {
}

lazy val DirectiveLocations: Parser0[List[Ast.DirectiveLocation]] =
keyword("|").? *> DirectiveLocation.repSep0(keyword("|"))
punctuation("|").? *> DirectiveLocation.repSep0(punctuation("|"))

lazy val DirectiveLocation: Parser[Ast.DirectiveLocation] =
keyword("QUERY") .as(Ast.DirectiveLocation.QUERY) |
Expand Down Expand Up @@ -229,7 +234,7 @@ object GraphQLParser {
lazy val SelectionSet: Parser[List[Ast.Selection]] = recursive[List[Ast.Selection]] { rec =>

val Alias: Parser[Ast.Name] =
Name <* keyword(":")
Name <* punctuation(":")

val Field: Parser[Ast.Selection.Field] =
(Alias.backtrack.?.with1 ~ Name ~ Arguments.? ~ Directives ~ rec.?).map {
Expand All @@ -246,7 +251,7 @@ object GraphQLParser {

val Selection: Parser[Ast.Selection] =
Field |
(keyword("...") *> (InlineFragment | FragmentSpread))
(punctuation("...") *> (InlineFragment | FragmentSpread))

braces(Selection.rep0)
}
Expand All @@ -255,7 +260,7 @@ object GraphQLParser {
parens(Argument.rep0)

lazy val Argument: Parser[(Ast.Name, Ast.Value)] =
(Name <* keyword(":")) ~ Value
(Name <* punctuation(":")) ~ Value

lazy val FragmentName: Parser[Ast.Name] =
not(string("on")).with1 *> Name
Expand Down Expand Up @@ -300,7 +305,7 @@ object GraphQLParser {
token(booleanLiteral).map(Ast.Value.BooleanValue.apply)

val ObjectField: Parser[(Ast.Name, Ast.Value)] =
(Name <* keyword(":")) ~ rec
(Name <* punctuation(":")) ~ rec

val ObjectValue: Parser[Ast.Value.ObjectValue] =
braces(ObjectField.rep0).map(Ast.Value.ObjectValue.apply)
Expand All @@ -322,27 +327,27 @@ object GraphQLParser {
parens(VariableDefinition.rep0)

lazy val VariableDefinition: Parser[Ast.VariableDefinition] =
((Variable <* keyword(":")) ~ Type ~ DefaultValue.? ~ Directives.?).map {
((Variable <* punctuation(":")) ~ Type ~ DefaultValue.? ~ Directives.?).map {
case (((v, tpe), dv), dirs) => Ast.VariableDefinition(v.name, tpe, dv, dirs.getOrElse(Nil))
}

lazy val Variable: Parser[Ast.Value.Variable] =
keyword("$") *> Name.map(Ast.Value.Variable.apply)
punctuation("$") *> Name.map(Ast.Value.Variable.apply)

lazy val DefaultValue: Parser[Ast.Value] =
keyword("=") *> Value
punctuation("=") *> Value

lazy val Type: Parser[Ast.Type] = recursive[Ast.Type] { rec =>

lazy val ListType: Parser[Ast.Type.List] =
squareBrackets(rec).map(Ast.Type.List.apply)

val namedMaybeNull: Parser[Ast.Type] = (NamedType ~ keyword("!").?).map {
val namedMaybeNull: Parser[Ast.Type] = (NamedType ~ punctuation("!").?).map {
case (t, None) => t
case (t, _) => Ast.Type.NonNull(Left(t))
}

val listMaybeNull: Parser[Ast.Type] = (ListType ~ keyword("!").?).map {
val listMaybeNull: Parser[Ast.Type] = (ListType ~ punctuation("!").?).map {
case (t, None) => t
case (t, _) => Ast.Type.NonNull(Right(t))
}
Expand All @@ -357,16 +362,12 @@ object GraphQLParser {
Directive.rep0

lazy val Directive: Parser[Ast.Directive] =
keyword("@") *> (Name ~ Arguments.?).map { case (n, ods) => Ast.Directive(n, ods.orEmpty)}
punctuation("@") *> (Name ~ Arguments.?).map { case (n, ods) => Ast.Directive(n, ods.orEmpty)}

lazy val Name: Parser[Ast.Name] = {
val initial = ('A' to 'Z') ++ ('a' to 'z') ++ Seq('_')
val subsequent = initial ++ ('0' to '9')

token(charIn(initial) ~ charIn(subsequent).rep0).map {
lazy val Name: Parser[Ast.Name] =
token(charIn(nameInitial) ~ charIn(nameSubsequent).rep0).map {
case (h, t) => Ast.Name((h :: t).mkString)
}
}

def toResult[T](text: String, pr: Either[Parser.Error, T]): Result[T] =
Result.fromEither(pr.leftMap { e =>
Expand Down
44 changes: 43 additions & 1 deletion modules/core/src/test/scala/parser/ParserSuite.scala
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,9 +15,10 @@

package parser

import cats.data.NonEmptyChain
import munit.CatsEffectSuite

import grackle.{ Ast, GraphQLParser }
import grackle.{Ast, GraphQLParser, Problem, Result}
import grackle.syntax._
import Ast._, OperationType._, OperationDefinition._, Selection._, Value._, Type.Named

Expand Down Expand Up @@ -610,4 +611,45 @@ final class ParserSuite extends CatsEffectSuite {
val res = GraphQLParser.Document.parseAll(schema).toOption
assert(res == Some(expected))
}

test("keywords parsed non-greedily (1)") {
val schema =
"""|extend type Name {
| value:String
|}""".stripMargin

val expected =
List(
ObjectTypeExtension(
Named(Name("Name")),
List(
FieldDefinition(Name("value"), None, Nil, Named(Name("String")), Nil)
),
Nil,
Nil
)
)

val res = GraphQLParser.Document.parseAll(schema).toOption
assertEquals(res, Some(expected))
}

test("keywords parsed non-greedily (2)") {
val schema =
"""|extendtypeName {
| value:String
|}""".stripMargin

val expected =
NonEmptyChain(
Problem(
"""|Parse error at line 0 column 6
|extendtypeName {
| ^""".stripMargin
)
)

val res = GraphQLParser.toResult(schema, GraphQLParser.Document.parseAll(schema))
assertEquals(res, Result.Failure(expected))
}
}

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