[JENKINS-51779] Avoid com.google.common.collect.Iterators.skip (#3481)

* [JENKINS-51779] Avoid com.google.common.collect.Iterators.skip.

* Reviewers preferred for the new method to be restricted for now.

core/src/main/java/hudson/util/Iterators.java

@@ -23,6 +23,7 @@
  */
 package hudson.util;
 
+import com.google.common.annotations.Beta;
 import com.google.common.base.Predicates;
 import com.google.common.collect.ImmutableList;
 
@@ -35,6 +36,9 @@
 import java.util.Arrays;
 import java.util.Set;
 import java.util.HashSet;
+import javax.annotation.Nonnull;
+import org.kohsuke.accmod.Restricted;
+import org.kohsuke.accmod.restrictions.NoExternalUse;
 
 /**
  * Varios {@link Iterator} implementations.
@@ -403,4 +407,20 @@ public void remove() {
     public interface CountingPredicate<T> {
         boolean apply(int index, T input);
     }
+
+    /**
+     * Similar to {@link com.google.common.collect.Iterators#skip} except not {@link Beta}.
+     * @param iterator some iterator
+     * @param count a nonnegative count
+     */
+    @Restricted(NoExternalUse.class)
+    public static void skip(@Nonnull Iterator<?> iterator, int count) {
+        if (count < 0) {
+            throw new IllegalArgumentException();
+        }
+        while (iterator.hasNext() && count-- > 0) {
+            iterator.next();
+        }
+    }
+
 }

core/src/main/java/hudson/util/RunList.java

@@ -150,7 +150,7 @@ public R get(int index) {
     public List<R> subList(int fromIndex, int toIndex) {
         List<R> r = new ArrayList<R>();
         Iterator<R> itr = iterator();
-        Iterators.skip(itr,fromIndex);
+        hudson.util.Iterators.skip(itr, fromIndex);
         for (int i=toIndex-fromIndex; i>0; i--) {
             r.add(itr.next());
         }

core/src/main/java/jenkins/widgets/HistoryPageFilter.java

@@ -24,14 +24,14 @@
 package jenkins.widgets;
 
 import com.google.common.collect.Iterables;
-import com.google.common.collect.Iterators;
 import hudson.model.AbstractBuild;
 import hudson.model.Job;
 import hudson.model.ParameterValue;
 import hudson.model.ParametersAction;
 import hudson.model.Queue;
 import hudson.model.Run;
 import hudson.search.UserSearchProperty;
+import hudson.util.Iterators;
 import hudson.widgets.HistoryWidget;
 
 import javax.annotation.Nonnull;

core/src/test/java/hudson/util/IteratorsTest.java

@@ -32,6 +32,7 @@
 import java.util.List;
 
 import org.junit.Test;
+import org.jvnet.hudson.test.Issue;
 
 /**
  * @author Kohsuke Kawaguchi
@@ -77,9 +78,27 @@ public void limit() {
         assertEquals("[]", com.google.common.collect.Iterators.toString(Iterators.limit(asList(1,2,4,6).iterator(), EVEN)));
     }
 
-    public static final CountingPredicate<Integer> EVEN = new CountingPredicate<Integer>() {
-        public boolean apply(int index, Integer input) {
-            return input % 2 == 0;
-        }
-    };
+    public static final CountingPredicate<Integer> EVEN = (index, input) -> input % 2 == 0;
+
+    @Issue("JENKINS-51779")
+    @Test
+    public void skip() {
+        List<Integer> lst = Iterators.sequence(1, 4);
+        Iterator<Integer> it = lst.iterator();
+        Iterators.skip(it, 0);
+        assertEquals("[1, 2, 3]", com.google.common.collect.Iterators.toString(it));
+        it = lst.iterator();
+        Iterators.skip(it, 1);
+        assertEquals("[2, 3]", com.google.common.collect.Iterators.toString(it));
+        it = lst.iterator();
+        Iterators.skip(it, 2);
+        assertEquals("[3]", com.google.common.collect.Iterators.toString(it));
+        it = lst.iterator();
+        Iterators.skip(it, 3);
+        assertEquals("[]", com.google.common.collect.Iterators.toString(it));
+        it = lst.iterator();
+        Iterators.skip(it, 4);
+        assertEquals("[]", com.google.common.collect.Iterators.toString(it));
+    }
+
 }