Add org.eclipse.help.internal.search.SearchIndex#customSearch(...)

This adds a `customSearch` method to the internal class
`org.eclipse.help.internal.search.SearchIndex`. The purpose is to be
able to implement a hybrid search that combines a semantic search with a
sparse keyword search. And the sparse keyword search uses the existing
`SearchIndex` via this new method.

Author: howlger

ua/org.eclipse.help.base/src/org/eclipse/help/internal/search/SearchIndex.java

@@ -35,6 +35,7 @@
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
+import java.util.function.BiConsumer;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipInputStream;
 
@@ -664,6 +665,29 @@ public void search(ISearchQuery searchQuery, ISearchHitCollector collector)
 		}
 	}
 
+	/**
+	 * Performs a custom query search on this index (experimental)
+	 */
+	public void customSearch(BiConsumer<IndexSearcher, AnalyzerDescriptor> customSearcher) {
+		try {
+			if (closed)
+				return;
+			registerSearch(Thread.currentThread());
+			if (closed)
+				return;
+			if (searcher == null) {
+				try {
+					openSearcher();
+				} catch (Exception e) {
+					ILog.of(getClass()).error("Failed to open search index. Index directory: " + indexDir, e); //$NON-NLS-1$
+				}
+			}
+			customSearcher.accept(searcher, analyzerDescriptor);
+		} finally {
+			unregisterSearch(Thread.currentThread());
+		}
+	}
+
 	@Override
 	public String getLocale() {
 		return locale;