Regex.unapplySeq should not take Any (Fixes SI-6406)

This deprecates unapplySeq(Any) and adds overloaded
unapplySeq(CharSequence) and unapplySeq(Match), with the
putative advantage that you can't try to extract the unextractable.

Regex is massaged so that the underlying Pattern is primary,
rather than the String-valued expression.  Regex and its
unanchored companion (I almost wrote unmoored) share a
Pattern object, so that unapplySeq(Match) can easily test
whether the Match was generated by this Regex; in that case,
the match result is used immediately, instead of reapplying
the regex to the matched string.

The documentation is massaged to reflect unanchored and also to
align with the underlying terminology, e.g., "subgroup" really
just means "group."

Author: som-snytt

src/library/scala/util/matching/Regex.scala

@@ -131,7 +131,7 @@ import java.util.regex.{ Pattern, Matcher }
  *  @author  Martin Odersky
  *  @version 1.1, 29/01/2008
  *
- *  @param regex      A string representing a regular expression
+ *  @param pattern    The compiled pattern
  *  @param groupNames A mapping from names to indices in capture groups
  *
  *  @define replacementString
@@ -144,41 +144,67 @@ import java.util.regex.{ Pattern, Matcher }
  *  to automatically escape these characters.
  */
 @SerialVersionUID(-2094783597747625537L)
-class Regex(regex: String, groupNames: String*) extends Serializable {
+class Regex private[matching](val pattern: Pattern, groupNames: String*) extends Serializable {
   outer =>
 
   import Regex._
 
-  /** The compiled pattern */
-  val pattern = Pattern.compile(regex)
+  /**
+    *  @param regex      A string representing a regular expression
+    *  @param groupNames A mapping from names to indices in capture groups
+    */
+  def this(regex: String, groupNames: String*) = this(Pattern.compile(regex), groupNames: _*)
 
-  /** Tries to match target (whole match) and returns the matching subgroups.
-   *  if the pattern has no subgroups, then it returns an empty list on a
-   *  successful match.
-   *
-   *  Note, however, that if some subgroup has not been matched, a `null` will
-   *  be returned for that subgroup.
+  /** Tries to match a [[java.lang.CharSequence]].
+   *  If the match succeeds, the result is a list of the matching
+   *  groups (or a `null` element if a group did not match any input).
+   *  If the pattern specifies no groups, then the result will be an empty list
+   *  on a successful match.
    *
+   *  This method attempts to match the entire input by default; to find the next
+   *  matching subsequence, use an unanchored Regex.
+
    *  For example:
    *
    *  {{{
    *  val p1 = "ab*c".r
-   *  val p2 = "a(b*)c".r
-   *
    *  val p1Matches = "abbbc" match {
    *    case p1() => true
    *    case _    => false
    *  }
-   *
+   *  val p2 = "a(b*)c".r
    *  val numberOfB = "abbbc" match {
    *    case p2(b) => Some(b.length)
    *    case _     => None
    *  }
+   *  val p3 = "b*".r.unanchored
+   *  val p3Matches = "abbbc" match {
+   *    case p3() => true
+   *    case _    => false
+   *  }
    *  }}}
    *
-   *  @param target The string to match
+   *  @param  s     The string to match
    *  @return       The matches
    */
+  def unapplySeq(s: CharSequence): Option[Seq[String]] = {
+    val m = pattern matcher s
+    if (runMatcher(m)) Some(1 to m.groupCount map m.group)
+    else None
+  }
+
+  /** Tries to match on a [[scala.util.matching.Regex.Match]].
+   *  A previously failed match results in None.
+   *  If a successful match was made against the current pattern, then that result is used.
+   *  Otherwise, this Regex is applied to the previously matched input,
+   *  and the result of that match is used.
+   */
+  def unapplySeq(m: Match): Option[Seq[String]] = 
+    if (m.matched == null) None
+    else if (m.matcher.pattern == this.pattern) Some(1 to m.groupCount map m.group)
+    else unapplySeq(m.matched)
+
+  @deprecated("Extracting a match result from anything but a CharSequence or Match is deprecated", "2.10.0")
   def unapplySeq(target: Any): Option[List[String]] = target match {
     case s: CharSequence =>
       val m = pattern matcher s
@@ -187,6 +213,8 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
     case m: Match        => unapplySeq(m.matched)
     case _               => None
   }
+
+  //  @see UnanchoredRegex
   protected def runMatcher(m: Matcher) = m.matches()
 
   /** Return all matches of this regexp in given character sequence as a [[scala.util.matching.Regex.MatchIterator]],
@@ -200,7 +228,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *  @return       A [[scala.util.matching.Regex.MatchIterator]] of all matches.
    *  @example      {{{for (words <- """\w+""".r findAllIn "A simple example.") yield words}}}
    */
-  def findAllIn(source: java.lang.CharSequence) = new Regex.MatchIterator(source, this, groupNames)
+  def findAllIn(source: CharSequence) = new Regex.MatchIterator(source, this, groupNames)
 
 
   /** Return all matches of this regexp in given character sequence as a
@@ -210,7 +238,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *  @return       A [[scala.collection.Iterator]] of [[scala.util.matching.Regex.Match]] for all matches.
    *  @example      {{{for (words <- """\w+""".r findAllMatchIn "A simple example.") yield words.start}}}
    */
-  def findAllMatchIn(source: java.lang.CharSequence): Iterator[Match] = {
+  def findAllMatchIn(source: CharSequence): Iterator[Match] = {
     val matchIterator = findAllIn(source)
     new Iterator[Match] {
       def hasNext = matchIterator.hasNext
@@ -228,7 +256,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *  @return       An [[scala.Option]] of the first matching string in the text.
    *  @example      {{{"""\w+""".r findFirstIn "A simple example." foreach println // prints "A"}}}
    */
-  def findFirstIn(source: java.lang.CharSequence): Option[String] = {
+  def findFirstIn(source: CharSequence): Option[String] = {
     val m = pattern.matcher(source)
     if (m.find) Some(m.group) else None
   }
@@ -245,7 +273,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *  @return       A [[scala.Option]] of [[scala.util.matching.Regex.Match]] of the first matching string in the text.
    *  @example      {{{("""[a-z]""".r findFirstMatchIn "A simple example.") map (_.start) // returns Some(2), the index of the first match in the text}}}
    */
-  def findFirstMatchIn(source: java.lang.CharSequence): Option[Match] = {
+  def findFirstMatchIn(source: CharSequence): Option[Match] = {
     val m = pattern.matcher(source)
     if (m.find) Some(new Match(source, m, groupNames)) else None
   }
@@ -262,7 +290,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *  @return       A [[scala.Option]] of the matched prefix.
    *  @example      {{{"""[a-z]""".r findPrefixOf "A simple example." // returns None, since the text does not begin with a lowercase letter}}}
    */
-  def findPrefixOf(source: java.lang.CharSequence): Option[String] = {
+  def findPrefixOf(source: CharSequence): Option[String] = {
     val m = pattern.matcher(source)
     if (m.lookingAt) Some(m.group) else None
   }
@@ -279,7 +307,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *  @return       A [[scala.Option]] of the [[scala.util.matching.Regex.Match]] of the matched string.
    *  @example      {{{"""\w+""".r findPrefixMatchOf "A simple example." map (_.after) // returns Some(" simple example.")}}}
    */
-  def findPrefixMatchOf(source: java.lang.CharSequence): Option[Match] = {
+  def findPrefixMatchOf(source: CharSequence): Option[Match] = {
     val m = pattern.matcher(source)
     if (m.lookingAt) Some(new Match(source, m, groupNames)) else None
   }
@@ -293,7 +321,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *  @return            The resulting string
    *  @example           {{{"""\d+""".r replaceAllIn ("July 15", "<NUMBER>") // returns "July <NUMBER>"}}}
    */
-  def replaceAllIn(target: java.lang.CharSequence, replacement: String): String = {
+  def replaceAllIn(target: CharSequence, replacement: String): String = {
     val m = pattern.matcher(target)
     m.replaceAll(replacement)
   }
@@ -316,7 +344,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    * @param replacer    The function which maps a match to another string.
    * @return            The target string after replacements.
    */
-  def replaceAllIn(target: java.lang.CharSequence, replacer: Match => String): String = {
+  def replaceAllIn(target: CharSequence, replacer: Match => String): String = {
     val it = new Regex.MatchIterator(target, this, groupNames).replacementData
     it foreach (md => it replace replacer(md))
     it.replaced
@@ -343,7 +371,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    * @param replacer    The function which optionally maps a match to another string.
    * @return            The target string after replacements.
    */
-  def replaceSomeIn(target: java.lang.CharSequence, replacer: Match => Option[String]): String = {
+  def replaceSomeIn(target: CharSequence, replacer: Match => Option[String]): String = {
     val it = new Regex.MatchIterator(target, this, groupNames).replacementData
     for (matchdata <- it ; replacement <- replacer(matchdata))
       it replace replacement
@@ -359,7 +387,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *  @param replacement The string that will replace the match
    *  @return            The resulting string
    */
-  def replaceFirstIn(target: java.lang.CharSequence, replacement: String): String = {
+  def replaceFirstIn(target: CharSequence, replacement: String): String = {
     val m = pattern.matcher(target)
     m.replaceFirst(replacement)
   }
@@ -370,7 +398,7 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *  @return        The array of strings computed by splitting the
    *                 input around matches of this regexp
    */
-  def split(toSplit: java.lang.CharSequence): Array[String] =
+  def split(toSplit: CharSequence): Array[String] =
     pattern.split(toSplit)
 
   /** Create a new Regex with the same pattern, but no requirement that
@@ -390,9 +418,11 @@ class Regex(regex: String, groupNames: String*) extends Serializable {
    *
    *  @return        The new unanchored regex
    */
-  def unanchored: UnanchoredRegex = new Regex(regex, groupNames: _*) with UnanchoredRegex { override def anchored = outer }
+  def unanchored: UnanchoredRegex = new Regex(pattern, groupNames: _*) with UnanchoredRegex { override def anchored = outer }
   def anchored: Regex             = this
 
+  def regex: String = pattern.pattern
+
   /** The string defining the regular expression */
   override def toString = regex
 }
@@ -421,7 +451,7 @@ object Regex {
   trait MatchData {
 
     /** The source from where the match originated */
-    val source: java.lang.CharSequence
+    val source: CharSequence
 
     /** The names of the groups, or some empty sequence if one defined */
     val groupNames: Seq[String]
@@ -459,25 +489,25 @@ object Regex {
 
     /** The char sequence before first character of match,
      *  or `null` if nothing was matched */
-    def before: java.lang.CharSequence =
+    def before: CharSequence =
       if (start >= 0) source.subSequence(0, start)
       else null
 
     /** The char sequence before first character of match in group `i`,
      *  or `null` if nothing was matched for that group  */
-    def before(i: Int): java.lang.CharSequence =
+    def before(i: Int): CharSequence =
       if (start(i) >= 0) source.subSequence(0, start(i))
       else null
 
     /** Returns char sequence after last character of match,
      *  or `null` if nothing was matched */
-    def after: java.lang.CharSequence =
+    def after: CharSequence =
       if (end >= 0) source.subSequence(end, source.length)
       else null
 
     /** The char sequence after last character of match in group `i`,
      *  or `null` if nothing was matched for that group  */
-    def after(i: Int): java.lang.CharSequence =
+    def after(i: Int): CharSequence =
       if (end(i) >= 0) source.subSequence(end(i), source.length)
       else null
 
@@ -501,8 +531,8 @@ object Regex {
 
   /** Provides information about a succesful match.
    */
-  class Match(val source: java.lang.CharSequence,
-              matcher: Matcher,
+  class Match(val source: CharSequence,
+              private[matching] val matcher: Matcher,
               val groupNames: Seq[String]) extends MatchData {
 
     /** The index of the first matched character */
@@ -563,7 +593,7 @@ object Regex {
 
   /** A class to step through a sequence of regex matches
    */
-  class MatchIterator(val source: java.lang.CharSequence, val regex: Regex, val groupNames: Seq[String])
+  class MatchIterator(val source: CharSequence, val regex: Regex, val groupNames: Seq[String])
   extends AbstractIterator[String] with Iterator[String] with MatchData { self =>
 
     protected[Regex] val matcher = regex.pattern.matcher(source)

test/files/neg/t6406-regextract.check

@@ -0,0 +1,6 @@
+t6406-regextract.scala:4: warning: method unapplySeq in class Regex is deprecated: Extracting a match result from anything but a CharSequence or Match is deprecated
+  List(1) collect { case r(i) => i }
+                         ^
+error: No warnings can be incurred under -Xfatal-warnings.
+one warning found
+one error found

test/files/neg/t6406-regextract.flags

@@ -0,0 +1 @@
+-Xfatal-warnings

test/files/neg/t6406-regextract.scala

@@ -0,0 +1,5 @@
+
+object Test extends App {
+  val r = "(\\d+)".r
+  List(1) collect { case r(i) => i }
+}

test/files/run/t6406-regextract.check

@@ -0,0 +1,4 @@
+List(1, 3)
+List(1, 3)
+List(1, 3)
+Some(2011) Some(2011)

test/files/run/t6406-regextract.scala

@@ -0,0 +1,30 @@
+
+object Test extends App {
+  import util.matching._
+  import Regex._
+
+  val r = "(\\d+)".r
+  val q = """(\d)""".r
+  val ns = List("1,2","x","3,4")
+  val u = r.unanchored
+
+  val is = ns collect { case u(x) => x } map { case r(x) => x }
+  println(is)
+  // Match from same pattern
+  val js = (ns map { u findFirstMatchIn _ }).flatten map { case r(x) => x }
+  println(js)
+  // Match not from same pattern
+  val ks = (ns map { q findFirstMatchIn _ }).flatten map { case r(x) => x }
+  println(ks)
+
+  val t = "Last modified 2011-07-15"
+  val p1 = """(\d\d\d\d)-(\d\d)-(\d\d)""".r
+  val y1: Option[String] = for {
+    p1(year, month, day) <- p1 findFirstIn t
+  } yield year
+  val y2: Option[String] = for {
+    p1(year, month, day) <- p1 findFirstMatchIn t
+  } yield year
+  println(s"$y1 $y2")
+
+}