Review Comments

opengrok-indexer/src/main/java/org/opengrok/indexer/util/ErrorMessageCollector.java

@@ -24,7 +24,6 @@
 package org.opengrok.indexer.util;
 
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
 
 import java.util.Collections;
 import java.util.Objects;
@@ -47,26 +46,31 @@ public class ErrorMessageCollector implements Collector<String, StringJoiner, Op
 
     private final String prefix;
     private final String emptyString;
-    private final Boolean returnNullWhenEmpty;
+    private final boolean returnNullWhenEmpty;
 
     /**
      * Creates a collector with given prefix and
      * returns optional empty for empty collection.
      * @param prefix prefix before the joined string
      */
     public ErrorMessageCollector(@NotNull String prefix) {
-        this(prefix, null);
+        Objects.requireNonNull(prefix);
+        this.prefix = prefix;
+        this.emptyString = "";
+        this.returnNullWhenEmpty = true;
     }
 
     /**
      * Creates a string joiner with given prefix and empty string.
      * @param prefix prefix before the joined string
-     * @param emptyString string to display if collection is empty, can be {@code null}
+     * @param emptyString string to display if collection is empty
      */
-    public ErrorMessageCollector(@NotNull String prefix, @Nullable String emptyString) {
+    public ErrorMessageCollector(@NotNull String prefix, @NotNull String emptyString) {
+        Objects.requireNonNull(prefix);
+        Objects.requireNonNull(emptyString);
         this.prefix = prefix;
-        this.emptyString = Objects.isNull(emptyString) ? "" : emptyString;
-        this.returnNullWhenEmpty = Objects.isNull(emptyString);
+        this.emptyString = emptyString;
+        this.returnNullWhenEmpty = false;
 
     }
     /**
@@ -77,7 +81,7 @@ public ErrorMessageCollector(@NotNull String prefix, @Nullable String emptyStrin
     @Override
     public Supplier<StringJoiner> supplier() {
         return () -> {
-            var joiner = new StringJoiner(", ", emptyString + prefix, "");
+            var joiner = new StringJoiner(", ", prefix, "");
             joiner.setEmptyValue(emptyString);
             return joiner;
         };

opengrok-indexer/src/main/java/org/opengrok/indexer/web/SearchHelper.java

@@ -401,7 +401,7 @@ public SearchHelper prepareExec(SortedSet<String> projects) {
                     searcher = RuntimeEnvironment.getInstance().getIndexSearcherFactory().newSearcher(reader);
                 } else {
                     errorMsg = projects.stream()
-                            .collect(new ErrorMessageCollector(" for projects: ",
+                            .collect(new ErrorMessageCollector("Failed to initialize search. Check the index for projects: ",
                                     "Failed to initialize search. Check the index"))
                             .orElse("");
                     return this;
@@ -430,7 +430,7 @@ public SearchHelper prepareExec(SortedSet<String> projects) {
         } catch (FileNotFoundException e) {
 
             errorMsg = projects.stream()
-                    .collect(new ErrorMessageCollector(" for projects: ",
+                    .collect(new ErrorMessageCollector("Index database not found. Check the index for projects: ",
                             "Index database not found. Check the index"))
                     .orElse("");
             errorMsg += "; " + e.getMessage();

opengrok-indexer/src/test/java/org/opengrok/indexer/util/ErrorMessageCollectorTest.java

@@ -0,0 +1,61 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * See LICENSE.txt included in this distribution for the specific
+ * language governing permissions and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at LICENSE.txt.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2023, Oracle and/or its affiliates.
+ * Portions Copyright (c) 2023, Gino Augustine <[email protected]>.
+ */
+package org.opengrok.indexer.util;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.Set;
+import java.util.stream.Stream;
+
+/**
+ * Represents a container for tests of {@link ErrorMessageCollector}.
+ */
+class ErrorMessageCollectorTest {
+    @Test
+    void noEmptyStringEmptyCollectionReturnOptionalEmpty() {
+        var collector = new ErrorMessageCollector("TestPrefix");
+        var returnValue = Stream.<String>empty().collect(collector);
+        Assertions.assertTrue(returnValue.isEmpty());
+    }
+    @Test
+    void emptyStringWithEmptyCollectionReturnOptionalEmpty() {
+        var collector = new ErrorMessageCollector("TestPrefix", "TestEmptyString");
+        var returnValue = Stream.<String>empty().collect(collector);
+        Assertions.assertEquals("TestEmptyString", returnValue.orElse(""));
+    }
+    @Test
+    void noEmptyStringWithMultiElementCollectionReturnJoinedString() {
+        var collector = new ErrorMessageCollector("TestPrefix ");
+        var returnValue = Set.of("a", "b").stream().collect(collector);
+        Assertions.assertTrue(returnValue.orElse("").startsWith("TestPrefix "));
+    }
+    @Test
+    void emptyStringWithMultiElementCollectionReturnJoinedStringWithoutEmptyString() {
+        var collector = new ErrorMessageCollector("TestPrefix ", "TestEmptyString");
+        var returnValue = Set.of("a", "b").stream().collect(collector);
+        Assertions.assertTrue(returnValue.orElse("").startsWith("TestPrefix "));
+    }
+
+}