Added an arabic snowball stemmer and test dataset

This change adds an Arabic snowball stemmer based on snowballstem.org
as well as an arabic test dataset in `TestSnowballVocabData.zip`
It also updates the `ant patch-snowball` target to be compatible with
the java classes generated by the last snowball version (tree:
1964ce688cbeca505263c8f77e16ed923296ce7a). The `ant patch-snowball` target
is retro-compatible with the version of snowball stemmers used in
lucene 7.x and ignores already patched classes.

Signed-off-by: Jim Ferenczi <jimczi@apache.org>

lucene/CHANGES.txt

@@ -226,6 +226,10 @@ New Features
 * LUCENE-8538: Add a Simple WKT Shape Parser for creating Lucene Geometries (Polygon, Line,
   Rectangle) from WKT format. (Nick Knize)
 
+* LUCENE-8462: Adds an Arabic snowball stemmer based on
+  https://github.com/snowballstem/snowball/blob/master/algorithms/arabic.sbl 
+  (Ryadh Dahimene via Jim Ferenczi)
+
 Improvements:
 
 * LUCENE-8521: Change LatLonShape encoding to 7 dimensions instead of 6; where the

lucene/analysis/common/build.xml

@@ -17,7 +17,7 @@
     limitations under the License.
  -->
 
-<project name="analyzers-common" default="default">
+<project name="analyzers-common" default="default" xmlns:rsel="antlib:org.apache.tools.ant.types.resources.selectors">
 
   <description>
     Analyzers for indexing content in different languages and domains.
@@ -129,12 +129,70 @@
 
   <target name="patch-snowball" description="Patches all snowball programs in '${snowball.programs.dir}' to make them work with MethodHandles">
     <fileset id="snowball.programs" dir="${snowball.programs.dir}" includes="*Stemmer.java"/>
+
     <replaceregexp match="^public class \w+Stemmer\b" replace="@SuppressWarnings(&quot;unused&quot;) \0" flags="m" encoding="UTF-8">
+      <restrict>
         <fileset refid="snowball.programs"/>
+        <rsel:not>
+          <rsel:contains text="patched"/>
+        </rsel:not>
+      </restrict>
     </replaceregexp>
-      <replaceregexp match="private final static \w+Stemmer methodObject\b.*$" replace="/* patched */ private static final java.lang.invoke.MethodHandles.Lookup methodObject = java.lang.invoke.MethodHandles.lookup();" flags="m" encoding="UTF-8">
+
+    <replaceregexp match="new Among\(([^,]*,[^,]*,[^,]*?)(?=\))" replace="\0, &quot;&quot;, methodObject" flags="g" encoding="UTF-8">
+      <restrict>
         <fileset refid="snowball.programs"/>
+        <rsel:not>
+          <rsel:contains text="patched"/>
+        </rsel:not>
+      </restrict>
     </replaceregexp>
+
+    <replaceregexp match="(new Among\([^,]*,[^,]*,[^,]*,[^,]*,)[^,]*?(?=\))" replace="\1 methodObject" flags="g" encoding="UTF-8">
+      <restrict>
+        <fileset refid="snowball.programs"/>
+        <rsel:not>
+          <rsel:contains text="patched"/>
+        </rsel:not>
+      </restrict>
+    </replaceregexp>
+
+    <replaceregexp match="(?:find_among(?:|_b)\()(.*?)(?=\))" replace="\0, \1.length" flags="g" encoding="UTF-8">
+      <restrict>
+        <fileset refid="snowball.programs"/>
+        <rsel:not>
+          <rsel:contains text="patched"/>
+        </rsel:not>
+      </restrict>
+    </replaceregexp>
+
+    <replaceregexp match="current" replace="getCurrent()" flags="g" encoding="UTF-8">
+      <restrict>
+        <fileset refid="snowball.programs"/>
+        <rsel:not>
+          <rsel:contains text="patched"/>
+        </rsel:not>
+      </restrict>
+    </replaceregexp>
+
+    <replaceregexp match="(?:eq_s(?:|_b)\()(.*?)(?=\))" replace="\0.length(),\1" flags="g" encoding="UTF-8">
+      <restrict>
+        <fileset refid="snowball.programs"/>
+        <rsel:not>
+          <rsel:contains text="patched"/>
+        </rsel:not>
+      </restrict>
+    </replaceregexp>
+
+    <replaceregexp match="private static final long serialVersionUID(.*)" replace="private static final long serialVersionUID = 1L; ${line.separator}${line.separator} /* patched */ private static final java.lang.invoke.MethodHandles.Lookup methodObject = java.lang.invoke.MethodHandles.lookup();" flags="m" encoding="UTF-8">
+      <restrict>
+        <fileset refid="snowball.programs"/>
+        <rsel:not>
+          <rsel:contains text="patched"/>
+        </rsel:not>
+      </restrict>
+    </replaceregexp>
+
     <fixcrlf srcdir="${snowball.programs.dir}" includes="*Stemmer.java" tab="remove" tablength="2" encoding="UTF-8" javafiles="yes" fixlast="yes"/>
   </target>
 </project>

lucene/analysis/common/src/test/org/apache/lucene/analysis/snowball/TestSnowballVocab.java

@@ -36,6 +36,7 @@ public class TestSnowballVocab extends LuceneTestCase {
    * Run all languages against their snowball vocabulary tests.
    */
   public void testStemmers() throws IOException {
+    assertCorrectOutput("Arabic", "arabic");
     assertCorrectOutput("Danish", "danish");
     assertCorrectOutput("Dutch", "dutch");
     assertCorrectOutput("English", "english");