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Defer creation of Expectations #280

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merged 6 commits into from Oct 29, 2021
Merged

Defer creation of Expectations #280

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ea427b9
Defer creation of expectations
rossabaker Oct 15, 2021
7de4372
scalafmt
rossabaker Oct 15, 2021
dedd158
s/Eval/thunks/g
rossabaker Oct 15, 2021
c52a6bb
Revert "s/Eval/thunks/g" -- not stack safe
rossabaker Oct 15, 2021
bbfe4d7
Add MiMa filter for CharIn.makeError
rossabaker Oct 15, 2021
9561249
Restore optimization from #62
rossabaker Oct 15, 2021
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8 changes: 7 additions & 1 deletion build.sbt
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@@ -1,3 +1,4 @@
import com.typesafe.tools.mima.core._
import sbtcrossproject.CrossPlugin.autoImport.{crossProject, CrossType}
import Dependencies._

Expand Down Expand Up @@ -133,7 +134,12 @@ lazy val core = crossProject(JSPlatform, JVMPlatform)
mimaPreviousArtifacts := {
val isScala211 = CrossVersion.partialVersion(scalaVersion.value).contains((2, 11))
if (isScala211) Set.empty else mimaPreviousArtifacts.value
}
},
mimaBinaryIssueFilters := Seq(
ProblemFilters.exclude[IncompatibleResultTypeProblem](
"cats.parse.Parser#Impl#CharIn.makeError"
) // Impl is private to cats.parse.Parser
)
)
.jsSettings(
crossScalaVersions := (ThisBuild / crossScalaVersions).value.filterNot(_.startsWith("2.11")),
Expand Down
72 changes: 45 additions & 27 deletions core/shared/src/main/scala/cats/parse/Parser.scala
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Expand Up @@ -68,7 +68,12 @@ sealed abstract class Parser0[+A] { self: Product =>
val offset = state.offset
if (err eq null) Right((str.substring(offset), result))
else
Left(Parser.Error(offset, Parser.Expectation.unify(NonEmptyList.fromListUnsafe(err.toList))))
Left(
Parser.Error(
offset,
Parser.Expectation.unify(NonEmptyList.fromListUnsafe(err.value.toList))
)
)
}

/** Attempt to parse all of the input `str` into an `A` value.
Expand All @@ -92,7 +97,12 @@ sealed abstract class Parser0[+A] { self: Product =>
)
)
} else
Left(Parser.Error(offset, Parser.Expectation.unify(NonEmptyList.fromListUnsafe(err.toList))))
Left(
Parser.Error(
offset,
Parser.Expectation.unify(NonEmptyList.fromListUnsafe(err.value.toList))
)
)
}

/** Convert epsilon failures into None values.
Expand Down Expand Up @@ -1773,7 +1783,7 @@ object Parser {
*/
protected[parse] final class State(val str: String) {
var offset: Int = 0
var error: Chain[Expectation] = null
var error: Eval[Chain[Expectation]] = null
var capture: Boolean = true
}

Expand Down Expand Up @@ -2033,7 +2043,8 @@ object Parser {
state.offset = end
res
} else {
state.error = Chain.one(Expectation.Length(offset, len, state.str.length - offset))
state.error =
Eval.later(Chain.one(Expectation.Length(offset, len, state.str.length - offset)))
null
}
}
Expand Down Expand Up @@ -2079,17 +2090,19 @@ object Parser {

case object StartParser extends Parser0[Unit] {
override def parseMut(state: State): Unit = {
if (state.offset != 0) {
state.error = Chain.one(Expectation.StartOfString(state.offset))
val offset = state.offset
if (offset != 0) {
state.error = Eval.later(Chain.one(Expectation.StartOfString(offset)))
}
()
}
}

case object EndParser extends Parser0[Unit] {
override def parseMut(state: State): Unit = {
if (state.offset != state.str.length) {
state.error = Chain.one(Expectation.EndOfString(state.offset, state.str.length))
val offset = state.offset
if (offset != state.str.length) {
state.error = Eval.later(Chain.one(Expectation.EndOfString(offset, state.str.length)))
}
()
}
Expand Down Expand Up @@ -2128,7 +2141,7 @@ object Parser {
state.offset += message.length
()
} else {
state.error = Chain.one(Expectation.OneOfStr(offset, message :: Nil))
state.error = Eval.later(Chain.one(Expectation.OneOfStr(offset, message :: Nil)))
()
}
}
Expand All @@ -2144,29 +2157,31 @@ object Parser {
state.offset += message.length
()
} else {
state.error = Chain.one(Expectation.OneOfStr(offset, message :: Nil))
state.error = Eval.later(Chain.one(Expectation.OneOfStr(offset, message :: Nil)))
()
}
}
}

case class Fail[A]() extends Parser[A] {
override def parseMut(state: State): A = {
state.error = Chain.one(Expectation.Fail(state.offset));
val offset = state.offset
state.error = Eval.later(Chain.one(Expectation.Fail(offset)))
null.asInstanceOf[A]
}
}

case class FailWith[A](message: String) extends Parser[A] {
override def parseMut(state: State): A = {
state.error = Chain.one(Expectation.FailWith(state.offset, message));
val offset = state.offset
state.error = Eval.later(Chain.one(Expectation.FailWith(offset, message)))
null.asInstanceOf[A]
}
}

final def oneOf[A](all: Array[Parser0[A]], state: State): A = {
val offset = state.offset
var errs: Chain[Expectation] = Chain.nil
var errs: Eval[Chain[Expectation]] = Eval.later(Chain.nil)
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@johnynek johnynek Oct 18, 2021 •
edited

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can we make this Eval.now(Chain.nil) I think that will be less allocation and actually every oneOf hits this path.

actually, can we allocate a single Eval[Chain[Expectation]] as a private val evalEmpty: Eval[Chain[Expectation]] = Eval.now(Chain.nil) in Impl and not have any allocations for this?

var idx = 0
while (idx < all.length) {
val thisParser = all(idx)
Expand All @@ -2180,7 +2195,7 @@ object Parser {
// we failed to parse, but didn't consume input
// is unchanged we continue
// else we stop
errs = errs ++ err
errs = errs.map(_ ++ err.value)
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.value isn't safe. We should do for { e1 <- errs; e2 <- err } yield (e1 ++ e2) or (errs, err).mapN(_ ++ _) but maybe the latter is slightly slower due to dispatch via typeclass.

state.error = null
idx = idx + 1
}
Expand Down Expand Up @@ -2221,7 +2236,7 @@ object Parser {
}
}
if (lastMatch < 0) {
state.error = Chain.one(Expectation.OneOfStr(startOffset, all.toList))
state.error = Eval.later(Chain.one(Expectation.OneOfStr(startOffset, all.toList)))
state.offset = startOffset
} else {
state.offset = lastMatch
Expand Down Expand Up @@ -2645,7 +2660,8 @@ object Parser {
state.offset += 1
char
} else {
state.error = Chain.one(Expectation.InRange(offset, Char.MinValue, Char.MaxValue))
state.error =
Eval.later(Chain.one(Expectation.InRange(offset, Char.MinValue, Char.MaxValue)))
'\u0000'
}
}
Expand All @@ -2656,15 +2672,17 @@ object Parser {

override def toString = s"CharIn($min, bitSet = ..., $ranges)"

def makeError(offset: Int): Chain[Expectation] = {
var result = Chain.empty[Expectation]
var aux = ranges.toList
while (aux.nonEmpty) {
val (s, e) = aux.head
result = result :+ Expectation.InRange(offset, s, e)
aux = aux.tail
def makeError(offset: Int): Eval[Chain[Expectation]] = {
Eval.later {
var result = Chain.empty[Expectation]
var aux = ranges.toList
while (aux.nonEmpty) {
val (s, e) = aux.head
result = result :+ Expectation.InRange(offset, s, e)
aux = aux.tail
}
result
}
result
}

override def parseMut(state: State): Char = {
Expand Down Expand Up @@ -2703,7 +2721,7 @@ object Parser {
val matchedStr = state.str.substring(offset, state.offset)
// we don't reset the offset, so if the underlying parser
// advanced it will fail in a OneOf
state.error = Chain.one(Expectation.ExpectedFailureAt(offset, matchedStr))
state.error = Eval.later(Chain.one(Expectation.ExpectedFailureAt(offset, matchedStr)))
}

state.offset = offset
Expand Down Expand Up @@ -2732,7 +2750,7 @@ object Parser {
override def parseMut(state: State): A = {
val a = under.parseMut(state)
if (state.error ne null) {
state.error = state.error.map(Expectation.WithContext(context, _))
state.error = state.error.map(_.map(Expectation.WithContext(context, _)))
}
a
}
Expand All @@ -2742,7 +2760,7 @@ object Parser {
override def parseMut(state: State): A = {
val a = under.parseMut(state)
if (state.error ne null) {
state.error = state.error.map(Expectation.WithContext(context, _))
state.error = state.error.map(_.map(Expectation.WithContext(context, _)))
}
a
}
Expand Down