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Use toVector for XML literal sequences
#23221
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toVector` for XML literal sequences (削除ここまで)toVector for XML literal sequences (追記ここまで)
I have a related PR to scala-xml which changes the API to return immutable.Seq instead of collection.Seq scala/scala-xml#760.
The current scala.xml.NodeSeq is only pretending to be immutable :)
$ scala repl -S 3 --dep org.scala-lang.modules::scala-xml:2.3.0 scala> import scala.xml._ scala> val x: collection.immutable.Seq[Node] = <a><b/></a> val x: Seq[scala.xml.Node] = <a><b/></a> scala> x.asInstanceOf[scala.xml.Node].child.asInstanceOf[scala.xml.NodeSeq].theSeq.asInstanceOf[NodeBuffer] += <c/> scala> x val res1: Seq[scala.xml.Node] = <a><b/><c/></a>
In `<a><b/><c/><a>`, a `NodeBuffer` (which extends `ArrayBuffer`) is
used to accumulate the children. The buffer is passed to
`new Elem($buf: _*)`, which only works thanks to the implicit
`collection.Seq[Node] => NodeSeq` declared in scala-xml.
With `-Vprint:typer`:
```scala
scala> <a><b/></a>
[[syntax trees at end of typer]] // rs$line1ドル
val res0: scala.xml.Elem =
{
new _root_.scala.xml.Elem(null, "a", _root_.scala.xml.Null,
scala.xml.TopScope, false,
{
val $buf: scala.xml.NodeBuffer = new _root_.scala.xml.NodeBuffer()
$buf.&+(
{
{
new _root_.scala.xml.Elem(null, "b", _root_.scala.xml.Null,
scala.xml.TopScope, true, [ : scala.xml.Node]*)
}
}
)
scala.xml.NodeSeq.seqToNodeSeq($buf)
}*
)
}
```
The implicit was not inserted in 2.12 because the varargs parameter of
Elem accepted a `collection.Seq`.
There is code that relies on XML sequences <a/><b/> having type NodeBuffer
<table>...</table><table>...</table> &+ getHTMLForCause(cause)
Method &+ is defined in NodeBuffer.
I narrowed the change so that plain XML sequences keep type NodeBuffer. Other XML sequences (children passed to Elem, children of <xml:group> passed to Group, attribute values with entity references passed to UnprefixedAttribute / PrefixedAttribute ) are converted toVector.
I know you have your reasons. But the dust you raise makes me sneeze. Oh it almost rhymes.
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Forward-port of scala/scala#11065
In
<a><b/><c/><a>, aNodeBuffer(which extendsArrayBuffer) is used to accumulate the children. The buffer is passed tonew Elem($buf: _*), which only works thanks to the implicitcollection.Seq[Node] => NodeSeqdeclared in scala-xml.With
-Vprint:typer:The implicit was not inserted in 2.12 because the varargs parameter of Elem accepted a
collection.Seq.