- B Sort map keys by toString if not Comparable

Fixes #650
When verifying a Map using StringUtils.toString(), keys are now sorted by their toString() representation if they do not implement Comparable. This prevents ClassCastExceptions. Added a test case with non-comparable keys using inline approvals.

Co-authored-by: Lars <LarsEckart@users.noreply.github.com>

Author: isidore

approvaltests-util-tests/src/test/java/com/spun/util/StringUtilsTest.java

@@ -8,6 +8,7 @@
 import org.junit.jupiter.api.Test;
 
 import java.util.Arrays;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.TreeMap;
@@ -101,6 +102,22 @@ void testSortedMap()
     sortedMap.put("zz", "1");
     Approvals.verify(sortedMap);
   }
+  @Test
+  void testMapWithNonComparableKeys()
+  {
+    var expected = """
+        a : first
+        m : middle
+        z : last
+        """;
+    Map<NonComparableKey, String> map = new HashMap<>();
+    // Add keys in a specific order to see if it's preserved or sorted later
+    map.put(new NonComparableKey("z"), "last");
+    map.put(new NonComparableKey("a"), "first");
+    map.put(new NonComparableKey("m"), "middle");
+    // Use inline approval with the expected sorted-by-toString output
+    Approvals.verify(map, new Options().inline(expected).withReporter(new AutoApproveReporter()));
+  }
   public class SplitUseCase
   {
     String   start;
@@ -160,4 +177,17 @@ public void testEnsureEnding()
     assertEquals(StringUtils.ensureEnding(first, "\n"), second);
     assertEquals(StringUtils.ensureEnding(second, "\n"), second);
   }
+  private static class NonComparableKey
+  {
+    private final String value;
+    public NonComparableKey(String value)
+    {
+      this.value = value;
+    }
+    @Override
+    public String toString()
+    {
+      return value;
+    }
+  }
 }

approvaltests-util/src/main/java/com/spun/util/StringUtils.java

@@ -2,6 +2,7 @@
 
 import org.lambda.functions.Function1;
 import org.lambda.query.Query;
+import org.lambda.query.Queryable;
 
 import java.io.ByteArrayInputStream;
 import java.io.InputStream;
@@ -10,6 +11,7 @@
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.Properties;
@@ -550,9 +552,17 @@ public static String toString(Map<?, ?> map)
   {
     StringBuffer b = new StringBuffer();
     Object[] keySet = map.keySet().toArray();
+    boolean isKeyComparable = ArrayUtils.isEmpty(keySet) || keySet[0] instanceof Comparable;
     if (!(map instanceof SortedMap))
     {
-      Arrays.sort(keySet);
+      if (isKeyComparable)
+      {
+        Arrays.sort(keySet);
+      }
+      else
+      {
+        Arrays.sort(keySet, Comparator.comparing(Object::toString));
+      }
     }
     for (Object key : keySet)
     {