Deprecate `nGram` and `edgeNGram` names for ngram filters (#30209)

The camel case name `nGram` should be removed in favour of `ngram` and
similar for `edgeNGram` and `edge_ngram`. Before removal, we need to
deprecate the camel case names first. This change adds deprecation
warnings for indices with versions 6.4.0 and higher and logs deprecation
warnings.

modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/CommonAnalysisPlugin.java

@@ -237,9 +237,14 @@ public class CommonAnalysisPlugin extends Plugin implements AnalysisPlugin {
         filters.add(PreConfiguredTokenFilter.singleton("dutch_stem", false, input -> new SnowballFilter(input, new DutchStemmer())));
         filters.add(PreConfiguredTokenFilter.singleton("edge_ngram", false, input ->
                 new EdgeNGramTokenFilter(input, EdgeNGramTokenFilter.DEFAULT_MIN_GRAM_SIZE, EdgeNGramTokenFilter.DEFAULT_MAX_GRAM_SIZE)));
-        // TODO deprecate edgeNGram
-        filters.add(PreConfiguredTokenFilter.singleton("edgeNGram", false, input ->
-                new EdgeNGramTokenFilter(input, EdgeNGramTokenFilter.DEFAULT_MIN_GRAM_SIZE, EdgeNGramTokenFilter.DEFAULT_MAX_GRAM_SIZE)));
+        filters.add(PreConfiguredTokenFilter.singletonWithVersion("edgeNGram", false, (reader, version) -> {
+            if (version.onOrAfter(org.elasticsearch.Version.V_6_4_0)) {
+                DEPRECATION_LOGGER.deprecatedAndMaybeLog("edgeNGram_deprecation",
+                        "The [edgeNGram] token filter name is deprecated and will be removed in a future version. "
+                                + "Please change the filter name to [edge_ngram] instead.");
+            }
+            return new EdgeNGramTokenFilter(reader, EdgeNGramTokenFilter.DEFAULT_MIN_GRAM_SIZE, EdgeNGramTokenFilter.DEFAULT_MAX_GRAM_SIZE);
+            }));
         filters.add(PreConfiguredTokenFilter.singleton("elision", true,
                 input -> new ElisionFilter(input, FrenchAnalyzer.DEFAULT_ARTICLES)));
         filters.add(PreConfiguredTokenFilter.singleton("french_stem", false, input -> new SnowballFilter(input, new FrenchStemmer())));
@@ -256,8 +261,14 @@ public class CommonAnalysisPlugin extends Plugin implements AnalysisPlugin {
                         LimitTokenCountFilterFactory.DEFAULT_MAX_TOKEN_COUNT,
                         LimitTokenCountFilterFactory.DEFAULT_CONSUME_ALL_TOKENS)));
         filters.add(PreConfiguredTokenFilter.singleton("ngram", false, NGramTokenFilter::new));
-        // TODO deprecate nGram
-        filters.add(PreConfiguredTokenFilter.singleton("nGram", false, NGramTokenFilter::new));
+        filters.add(PreConfiguredTokenFilter.singletonWithVersion("nGram", false, (reader, version) -> {
+            if (version.onOrAfter(org.elasticsearch.Version.V_6_4_0)) {
+                DEPRECATION_LOGGER.deprecatedAndMaybeLog("nGram_deprecation",
+                        "The [nGram] token filter name is deprecated and will be removed in a future version. "
+                                + "Please change the filter name to [ngram] instead.");
+            }
+            return new NGramTokenFilter(reader);
+        }));
         filters.add(PreConfiguredTokenFilter.singleton("persian_normalization", true, PersianNormalizationFilter::new));
         filters.add(PreConfiguredTokenFilter.singleton("porter_stem", false, PorterStemFilter::new));
         filters.add(PreConfiguredTokenFilter.singleton("reverse", false, ReverseStringFilter::new));

modules/analysis-common/src/test/java/org/elasticsearch/analysis/common/CommonAnalysisPluginTests.java

@@ -0,0 +1,119 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.analysis.common;
+
+import org.apache.lucene.analysis.MockTokenizer;
+import org.apache.lucene.analysis.Tokenizer;
+import org.elasticsearch.Version;
+import org.elasticsearch.cluster.metadata.IndexMetaData;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.env.Environment;
+import org.elasticsearch.index.IndexSettings;
+import org.elasticsearch.index.analysis.TokenFilterFactory;
+import org.elasticsearch.test.ESTestCase;
+import org.elasticsearch.test.IndexSettingsModule;
+import org.elasticsearch.test.VersionUtils;
+
+import java.io.IOException;
+import java.io.StringReader;
+import java.util.Map;
+
+public class CommonAnalysisPluginTests extends ESTestCase {
+
+    /**
+     * Check that the deprecated name "nGram" issues a deprecation warning for indices created since 6.3.0
+     */
+    public void testNGramDeprecationWarning() throws IOException {
+        Settings settings = Settings.builder().put(Environment.PATH_HOME_SETTING.getKey(), createTempDir())
+                .put(IndexMetaData.SETTING_VERSION_CREATED, VersionUtils.randomVersionBetween(random(), Version.V_6_4_0, Version.CURRENT))
+                .build();
+
+        IndexSettings idxSettings = IndexSettingsModule.newIndexSettings("index", settings);
+        try (CommonAnalysisPlugin commonAnalysisPlugin = new CommonAnalysisPlugin()) {
+            Map<String, TokenFilterFactory> tokenFilters = createTestAnalysis(idxSettings, settings, commonAnalysisPlugin).tokenFilter;
+            TokenFilterFactory tokenFilterFactory = tokenFilters.get("nGram");
+            Tokenizer tokenizer = new MockTokenizer();
+            tokenizer.setReader(new StringReader("foo bar"));
+            assertNotNull(tokenFilterFactory.create(tokenizer));
+            assertWarnings(
+                    "The [nGram] token filter name is deprecated and will be removed in a future version. "
+                    + "Please change the filter name to [ngram] instead.");
+        }
+    }
+
+    /**
+     * Check that the deprecated name "nGram" does NOT issues a deprecation warning for indices created before 6.4.0
+     */
+    public void testNGramNoDeprecationWarningPre6_4() throws IOException {
+        Settings settings = Settings.builder().put(Environment.PATH_HOME_SETTING.getKey(), createTempDir())
+                .put(IndexMetaData.SETTING_VERSION_CREATED,
+                        VersionUtils.randomVersionBetween(random(), Version.V_5_0_0, Version.V_6_3_0))
+                .build();
+
+        IndexSettings idxSettings = IndexSettingsModule.newIndexSettings("index", settings);
+        try (CommonAnalysisPlugin commonAnalysisPlugin = new CommonAnalysisPlugin()) {
+            Map<String, TokenFilterFactory> tokenFilters = createTestAnalysis(idxSettings, settings, commonAnalysisPlugin).tokenFilter;
+            TokenFilterFactory tokenFilterFactory = tokenFilters.get("nGram");
+            Tokenizer tokenizer = new MockTokenizer();
+            tokenizer.setReader(new StringReader("foo bar"));
+            assertNotNull(tokenFilterFactory.create(tokenizer));
+        }
+    }
+
+    /**
+     * Check that the deprecated name "edgeNGram" issues a deprecation warning for indices created since 6.3.0
+     */
+    public void testEdgeNGramDeprecationWarning() throws IOException {
+        Settings settings = Settings.builder().put(Environment.PATH_HOME_SETTING.getKey(), createTempDir())
+                .put(IndexMetaData.SETTING_VERSION_CREATED, VersionUtils.randomVersionBetween(random(), Version.V_6_4_0, Version.CURRENT))
+                .build();
+
+        IndexSettings idxSettings = IndexSettingsModule.newIndexSettings("index", settings);
+        try (CommonAnalysisPlugin commonAnalysisPlugin = new CommonAnalysisPlugin()) {
+            Map<String, TokenFilterFactory> tokenFilters = createTestAnalysis(idxSettings, settings, commonAnalysisPlugin).tokenFilter;
+            TokenFilterFactory tokenFilterFactory = tokenFilters.get("edgeNGram");
+            Tokenizer tokenizer = new MockTokenizer();
+            tokenizer.setReader(new StringReader("foo bar"));
+            assertNotNull(tokenFilterFactory.create(tokenizer));
+            assertWarnings(
+                    "The [edgeNGram] token filter name is deprecated and will be removed in a future version. "
+                    + "Please change the filter name to [edge_ngram] instead.");
+        }
+    }
+
+    /**
+     * Check that the deprecated name "edgeNGram" does NOT issues a deprecation warning for indices created before 6.4.0
+     */
+    public void testEdgeNGramNoDeprecationWarningPre6_4() throws IOException {
+        Settings settings = Settings.builder().put(Environment.PATH_HOME_SETTING.getKey(), createTempDir())
+                .put(IndexMetaData.SETTING_VERSION_CREATED,
+                        VersionUtils.randomVersionBetween(random(), Version.V_5_0_0, Version.V_6_3_0))
+                .build();
+
+        IndexSettings idxSettings = IndexSettingsModule.newIndexSettings("index", settings);
+        try (CommonAnalysisPlugin commonAnalysisPlugin = new CommonAnalysisPlugin()) {
+            Map<String, TokenFilterFactory> tokenFilters = createTestAnalysis(idxSettings, settings, commonAnalysisPlugin).tokenFilter;
+            TokenFilterFactory tokenFilterFactory = tokenFilters.get("edgeNGram");
+            Tokenizer tokenizer = new MockTokenizer();
+            tokenizer.setReader(new StringReader("foo bar"));
+            assertNotNull(tokenFilterFactory.create(tokenizer));
+        }
+    }
+}

modules/analysis-common/src/test/java/org/elasticsearch/analysis/common/NGramTokenizerFactoryTests.java

@@ -32,15 +32,11 @@ import org.elasticsearch.index.Index;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.test.ESTokenStreamTestCase;
 import org.elasticsearch.test.IndexSettingsModule;
+import org.elasticsearch.test.VersionUtils;
 
 import java.io.IOException;
 import java.io.StringReader;
-import java.lang.reflect.Field;
-import java.lang.reflect.Modifier;
-import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.List;
-import java.util.Random;
 
 import static com.carrotsearch.randomizedtesting.RandomizedTest.scaledRandomIntBetween;
 import static org.hamcrest.Matchers.instanceOf;
@@ -129,7 +125,7 @@ public class NGramTokenizerFactoryTests extends ESTokenStreamTestCase {
         for (int i = 0; i < iters; i++) {
             final Index index = new Index("test", "_na_");
             final String name = "ngr";
-            Version v = randomVersion(random());
+            Version v = VersionUtils.randomVersion(random());
             Builder builder = newAnalysisSettingsBuilder().put("min_gram", 2).put("max_gram", 3);
             boolean reverse = random().nextBoolean();
             if (reverse) {
@@ -150,7 +146,6 @@ public class NGramTokenizerFactoryTests extends ESTokenStreamTestCase {
         }
     }
 
-
     /*`
     * test that throws an error when trying to get a NGramTokenizer where difference between max_gram and min_gram
     * is greater than the allowed value of max_ngram_diff
@@ -175,16 +170,4 @@ public class NGramTokenizerFactoryTests extends ESTokenStreamTestCase {
                 + IndexSettings.MAX_NGRAM_DIFF_SETTING.getKey() + "] index level setting.",
             ex.getMessage());
     }
-
-    private Version randomVersion(Random random) throws IllegalArgumentException, IllegalAccessException {
-        Field[] declaredFields = Version.class.getFields();
-        List<Field> versionFields = new ArrayList<>();
-        for (Field field : declaredFields) {
-            if ((field.getModifiers() & Modifier.STATIC) != 0 && field.getName().startsWith("V_") && field.getType() == Version.class) {
-                versionFields.add(field);
-            }
-        }
-        return (Version) versionFields.get(random.nextInt(versionFields.size())).get(Version.class);
-    }
-
 }

server/src/main/java/org/elasticsearch/index/analysis/PreConfiguredTokenFilter.java

@@ -41,6 +41,15 @@ public final class PreConfiguredTokenFilter extends PreConfiguredAnalysisCompone
                 (tokenStream, version) -> create.apply(tokenStream));
     }
 
+    /**
+     * Create a pre-configured token filter that may not vary at all.
+     */
+    public static PreConfiguredTokenFilter singletonWithVersion(String name, boolean useFilterForMultitermQueries,
+            BiFunction<TokenStream, Version, TokenStream> create) {
+        return new PreConfiguredTokenFilter(name, useFilterForMultitermQueries, CachingStrategy.ONE,
+                (tokenStream, version) -> create.apply(tokenStream, version));
+    }
+
     /**
      * Create a pre-configured token filter that may vary based on the Lucene version.
      */