Log deprecation for nGram and edgeNGram custom filters (elastic#50376)

The camel-case `nGram` and `edgeNGram` filter names were deprecated in 6. We
currently throw errors on new indices when they are used. However these errors
are currently only thrown for pre-configured filters, adding them as custom
filters doesn't trigger the warning and error. This change adds the appropriate
deprecation warnings for `nGram` and `edgeNGram` respectively on version 7
indices.

Relates elastic#50360

Author: Christoph Büscher

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

@@ -118,9 +118,11 @@
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.regex.Regex;
+import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.NamedXContentRegistry;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.env.NodeEnvironment;
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.analysis.AnalyzerProvider;
 import org.elasticsearch.index.analysis.CharFilterFactory;
 import org.elasticsearch.index.analysis.PreBuiltAnalyzerProviderFactory;
@@ -242,7 +244,12 @@ public Map<String, AnalysisProvider<TokenFilterFactory>> getTokenFilters() {
         filters.put("dictionary_decompounder", requiresAnalysisSettings(DictionaryCompoundWordTokenFilterFactory::new));
         filters.put("dutch_stem", DutchStemTokenFilterFactory::new);
         filters.put("edge_ngram", EdgeNGramTokenFilterFactory::new);
-        filters.put("edgeNGram", EdgeNGramTokenFilterFactory::new);
+        filters.put("edgeNGram", (IndexSettings indexSettings, Environment environment, String name, Settings settings) -> {
+            deprecationLogger.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 EdgeNGramTokenFilterFactory(indexSettings, environment, name, settings);
+        });
         filters.put("elision", requiresAnalysisSettings(ElisionTokenFilterFactory::new));
         filters.put("fingerprint", FingerprintTokenFilterFactory::new);
         filters.put("flatten_graph", FlattenGraphTokenFilterFactory::new);
@@ -262,7 +269,12 @@ public Map<String, AnalysisProvider<TokenFilterFactory>> getTokenFilters() {
         filters.put("min_hash", MinHashTokenFilterFactory::new);
         filters.put("multiplexer", MultiplexerTokenFilterFactory::new);
         filters.put("ngram", NGramTokenFilterFactory::new);
-        filters.put("nGram", NGramTokenFilterFactory::new);
+        filters.put("nGram", (IndexSettings indexSettings, Environment environment, String name, Settings settings) -> {
+            deprecationLogger.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 NGramTokenFilterFactory(indexSettings, environment, name, settings);
+        });
         filters.put("pattern_capture", requiresAnalysisSettings(PatternCaptureGroupTokenFilterFactory::new));
         filters.put("pattern_replace", requiresAnalysisSettings(PatternReplaceTokenFilterFactory::new));
         filters.put("persian_normalization", PersianNormalizationFilterFactory::new);

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

@@ -169,4 +169,43 @@ public void testStandardHtmlStripAnalyzerDeprecationWarning() throws IOException
                     "replace it with a custom analyzer using [standard] tokenizer and [html_strip] char_filter, plus [lowercase] filter");
         }
     }
+
+    /**
+     * Check that the deprecated "nGram" filter logs a warning when the filter is used as a custom filter
+     */
+    public void testnGramFilterInCustomAnalyzerDeprecationError() throws IOException {
+        final Settings settings = Settings.builder().put(Environment.PATH_HOME_SETTING.getKey(), createTempDir())
+            .put(IndexMetaData.SETTING_VERSION_CREATED,
+                VersionUtils.randomVersionBetween(random(), Version.V_7_0_0, Version.CURRENT))
+            .put("index.analysis.analyzer.custom_analyzer.type", "custom")
+            .put("index.analysis.analyzer.custom_analyzer.tokenizer", "standard")
+            .putList("index.analysis.analyzer.custom_analyzer.filter", "my_ngram")
+            .put("index.analysis.filter.my_ngram.type", "nGram")
+            .build();
+
+        final CommonAnalysisPlugin commonAnalysisPlugin = new CommonAnalysisPlugin();
+
+        createTestAnalysis(IndexSettingsModule.newIndexSettings("index", settings), settings, commonAnalysisPlugin);
+        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 "edgeNGram" filter logs a warning when the filter is used as a custom filter
+     */
+    public void testEdgeNGramFilterInCustomAnalyzerDeprecationError() throws IOException {
+        final Settings settings = Settings.builder().put(Environment.PATH_HOME_SETTING.getKey(), createTempDir())
+            .put(IndexMetaData.SETTING_VERSION_CREATED,
+                VersionUtils.randomVersionBetween(random(), Version.V_7_0_0, Version.CURRENT))
+            .put("index.analysis.analyzer.custom_analyzer.type", "custom")
+            .put("index.analysis.analyzer.custom_analyzer.tokenizer", "standard")
+            .putList("index.analysis.analyzer.custom_analyzer.filter", "my_ngram")
+            .put("index.analysis.filter.my_ngram.type", "edgeNGram")
+            .build();
+        final CommonAnalysisPlugin commonAnalysisPlugin = new CommonAnalysisPlugin();
+
+        createTestAnalysis(IndexSettingsModule.newIndexSettings("index", settings), settings, commonAnalysisPlugin);
+        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.");
+    }
 }