Add continuously growing collection Generators

core/shared/src/main/scala/org/scalacheck/Gen.scala

@@ -1001,6 +1001,70 @@ object Gen extends GenArities with GenVersionSpecific {
     }
   }
 
+  /** Generates a container of any Traversable type for which there exists an
+   *  implicit [[org.scalacheck.util.Buildable]] instance. The elements in the
+   *  container will be generated by the given generator. The generated container
+   *  will continuously grow in size until the `fillCondition` returns true.
+   *  If the given generator fails generating a value, the
+   *  complete container generator will also fail. */
+  def buildableOfCond[C,T](fillCondition: C => Boolean, g: Gen[T], failureHint: Int= Integer.MAX_VALUE)(implicit
+    evb: Buildable[T,C], evt: C => Traversable[T]
+  ): Gen[C] = {
+    new Gen[C] {
+      def doApply(p: P, seed0: Seed): R[C] = {
+        var seed: Seed = p.initialSeed.getOrElse(seed0)
+        val bldr = evb.builder
+        val allowedFailures = Gen.collectionRetries(failureHint)
+        var failures = 0
+        while (!fillCondition(bldr.result)) {
+          val res = g.doApply(p, seed)
+          res.retrieve match {
+            case Some(t) =>
+              bldr += t
+            case None =>
+              failures += 1
+              if (failures >= allowedFailures) return r(None, res.seed)
+          }
+          seed = res.seed
+        }
+        r(Some(bldr.result), seed)
+      }
+    }
+  }
+
+  /** Generates a container of any Traversable type for which there exists an
+   *  implicit [[org.scalacheck.util.Buildable]] instance. The elements in the
+   *  container will be generated by the given generator. The generated container
+   *  will continuously frow in size until the `fillCondition` returns true.
+   *  Unlike `buildableOfCond`, this version of the method lets you specify another
+   *  collection Gen which helps in speeding up the process of growing the collection.
+   *  If the given generator fails generating a value, the
+   *  complete container generator will also fail. */
+  def buildableOfCollCond[C <: Traversable[T],T](cond: C => Boolean, g: Gen[C], failureHint: Int= Integer.MAX_VALUE)(implicit
+    evb: Buildable[T,C], evt: C => Traversable[T]
+  ): Gen[C] = {
+    new Gen[C] {
+      def doApply(p: P, seed0: Seed): R[C] = {
+        var seed: Seed = p.initialSeed.getOrElse(seed0)
+        val bldr = evb.builder
+        val allowedFailures = Gen.collectionRetries(failureHint)
+        var failures = 0
+        while (!cond(bldr.result)) {
+          val res = g.doApply(p, seed)
+          res.retrieve match {
+            case Some(t) =>
+              bldr ++= t
+            case None =>
+              failures += 1
+              if (failures >= allowedFailures) return r(None, res.seed)
+          }
+          seed = res.seed
+        }
+        r(Some(bldr.result), seed)
+      }
+    }
+  }
+
   /** Generates a container of any Traversable type for which there exists an
    *  implicit [[org.scalacheck.util.Buildable]] instance. The elements in the
    *  container will be generated by the given generator. The size of the
@@ -1042,6 +1106,18 @@ object Gen extends GenArities with GenVersionSpecific {
    *  `containerOf[List,T](g)`. */
   def listOf[T](g: => Gen[T]) = buildableOf[List[T], T](g)
 
+  /** Generates a list that continuously grows in size until
+   *  `finishCondition` returns true. */
+  def listOfCond[T](finishCondition: List[T] => Boolean, g: => Gen[T], failureHint: Int = Integer.MAX_VALUE) =
+    buildableOfCond[List[T], T](finishCondition, g, failureHint)
+
+  /** Generates a list that continuously grows in size until
+   *  `finishCondition` returns true. Unlike `listOfCond` it
+   *  accepts a list generator argument which lets you generate
+   *  larger lists quicker */
+  def listOfFillCond[T](finishCondition: List[T] => Boolean, g: => Gen[List[T]], failureHint: Int = Integer.MAX_VALUE) =
+    buildableOfCollCond[List[T], T](finishCondition, g, failureHint)
+
   /** Generates a non-empty list of random length. The maximum length depends
    *  on the size parameter. This method is equal to calling
    *  `nonEmptyContainerOf[List,T](g)`. */
@@ -1056,6 +1132,16 @@ object Gen extends GenArities with GenVersionSpecific {
    *  <code>containerOf[Map,(T,U)](g)</code>. */
   def mapOf[T, U](g: => Gen[(T, U)]) = buildableOf[Map[T, U], (T, U)](g)
 
+  /** Generates a map that continuously grows in size until
+   *  `finishCondition` returns true. */
+  def mapOfCond[T, U](cond: Map[T,U] => Boolean, g: => Gen[(T, U)], failureHint: Int = Integer.MAX_VALUE) = buildableOfCond[Map[T, U],(T, U)](cond, g, failureHint)
+
+  /** Generates a map that continuously grows in size until
+   *  `finishCondition` returns true. Unlike `mapOfCond` it
+   *  accepts a map generator argument which lets you generate
+   *  larger maps quicker */
+  def mapOfFillCond[T, U](cond: Map[T,U] => Boolean, g: => Gen[Map[T, U]], failureHint: Int = Integer.MAX_VALUE) = buildableOfCollCond[Map[T, U],(T, U)](cond, g, failureHint)
+
   /** Generates a non-empty map of random length. The maximum length depends
    *  on the size parameter. This method is equal to calling
    *  <code>nonEmptyContainerOf[Map,(T,U)](g)</code>. */