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Utility.trim collapse whitespace for adjacent text nodes #73 #113

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May 24, 2018
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Utility.trim collapse whitespace for adjacent text nodes #73 #113

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9b4e969
Unit tests for Issue #73
EdgeCaseBerg Oct 6, 2016
1e3b288
Unit tests for #73 passing
EdgeCaseBerg Oct 6, 2016
361d02e
Improve combineAdjacentTextNodes logic
EdgeCaseBerg May 11, 2018
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15 changes: 13 additions & 2 deletions shared/src/main/scala/scala/xml/Utility.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -46,17 +46,28 @@ object Utility extends AnyRef with parsing.TokenTests {
*/
def trim(x: Node): Node = x match {
case Elem(pre, lab, md, scp, child@_*) =>
val children = child flatMap trimProper
val children = combineAdjacentTextNodes(child:_*) flatMap trimProper
Elem(pre, lab, md, scp, children.isEmpty, children: _*)
}

private def combineAdjacentTextNodes(children: Node*): Seq[Node] = {
children.foldLeft(Seq.empty[Node]) { (acc, n) =>
(acc.lastOption, n) match {
case (Some(Text(l)), Text(r)) => {
acc.dropRight(1) :+ Text(l + r)
}
case _ => acc :+ n
}
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Hey Ethan,

This pattern match is kind of hairy.

Couldn't you drop the lastOption business, use foldRight, and have it just be the following?

      case (Text(l), Text(r) +: tt) => Text(l + r) +: tt
      case (t, tt) => t +: tt

Will it have the same result? Does that improve comprehensibility, as well?

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Right, foldRight I always use foldLeft so it never comes to mind. That would work,

import scala.xml._
val node = <A><One>1</One>{Text("Hello ")}{Text("World")}{Text(" I like pie.")}<Two>2</Two><Three><Nope>no</Nope></Three></A>

node.child.foldRight(Seq.empty[Node]) {
	case (Text(left), Text(right) +: accMinusLast) => Text(left + right) +: accMinusLast
	case (n, acc) => n +: acc 
}

// Seq[scala.xml.Node] = List(<One>1</One>, Hello World I like pie., <Two>2</Two>, <Three><Nope>no</Nope></Three>)

Looks like it would. I wasn't aware you can pattern match the last element in a list but I think that code is more elegant so I can update the PR with that and the tests will inform us if we're getting the same result (answer is probably yes)

}
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@ashawley ashawley May 11, 2018 •
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I wasn't aware you can pattern match the last element in a list

It is pattern matching the front of the list with foldRight ("fold right starts from the left" is how I remember it). Is it important to start from the end? I presume it's not. You're just trying to merge adjacent Texts I think.

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Oops sorry, I think I wrote that when I was tired this morning and reading +: as :+ and thinking out loud about

scala> val (last :+ list) = Seq(1,2,3,4)
last: Seq[Int] = List(1, 2, 3)
list: Int = 4

Correct that the order doesn't matter so long as the accumulated list is properly prepended/appended according to the direction it was traversed.

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Ah, ok. Yeah, it's a lot for a person to keep in their head... between the colons, plus signs and foldings.

}

/**
* trim a child of an element. `Attribute` values and `Atom` nodes that
* are not `Text` nodes are unaffected.
*/
def trimProper(x: Node): Seq[Node] = x match {
case Elem(pre, lab, md, scp, child@_*) =>
val children = child flatMap trimProper
val children = combineAdjacentTextNodes(child:_*) flatMap trimProper
Elem(pre, lab, md, scp, children.isEmpty, children: _*)
case Text(s) =>
new TextBuffer().append(s).toText
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23 changes: 23 additions & 0 deletions shared/src/test/scala/scala/xml/UtilityTest.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -194,4 +194,27 @@ class UtilityTest {
).toMap.withDefault {
key: Char => key.toString
}

def issue73StartsWithAndEndsWithWSInFirst: Unit = {
val x = <div>{Text(" My name is ")}{Text("Harry")}</div>
assertEquals(<div>My name is Harry</div>, Utility.trim(x))
}

@Test
def issue73EndsWithWSInLast: Unit = {
val x = <div>{Text("My name is ")}{Text("Harry ")}</div>
assertEquals(<div>My name is Harry</div>, Utility.trim(x))
}

@Test
def issue73HasWSInMiddle: Unit = {
val x = <div>{Text("My name is")}{Text(" ")}{Text("Harry")}</div>
assertEquals(<div>My name is Harry</div>, Utility.trim(x))
}

@Test
def issue73HasWSEverywhere: Unit = {
val x = <div>{Text(" My name ")}{Text(" is ")}{Text(" Harry ")}</div>
assertEquals(<div>My name is Harry</div>, Utility.trim(x))
}
}