Fix tostring formatter for child fields

.gitignore

@@ -19,3 +19,5 @@ target/
 
 target/
 .bsp/
+
+.uuid

api/src/main/java/com/tersesystems/echopraxia/spi/DefaultToStringFormatter.java

@@ -12,21 +12,20 @@ public class DefaultToStringFormatter implements ToStringFormatter {
   @Override
   @NotNull
   public String formatField(@NotNull Field field) {
-    StringBuilder builder = new StringBuilder();
-
-    if (field.attributes().containsKey(TOSTRING_FORMAT)) {
-      FieldVisitor fieldVisitor = field.attributes().get(TOSTRING_FORMAT);
-      assert fieldVisitor != null;
-      field = fieldVisitor.visit(field);
-    }
-
     if (isElided(field)) {
       return "";
     }
 
+    StringBuilder builder = new StringBuilder();
     if (!isValueOnly(field)) {
       formatName(builder, field.name(), field.attributes());
     }
+
+    if (field.attributes().containsKey(TOSTRING_FORMAT)) {
+      FieldVisitor fieldVisitor = field.attributes().get(TOSTRING_FORMAT);
+      assert fieldVisitor != null;
+      field = fieldVisitor.visit(field);
+    }
     formatValue(builder, field.value(), field.attributes());
     return builder.toString();
   }
@@ -107,6 +106,12 @@ private void formatObject(@NotNull StringBuilder b, @NotNull Value.ObjectValue v
         if (!isValueOnly(field)) {
           formatName(b, field.name(), field.attributes());
         }
+
+        if (field.attributes().containsKey(TOSTRING_FORMAT)) {
+          FieldVisitor fieldVisitor = field.attributes().get(TOSTRING_FORMAT);
+          assert fieldVisitor != null;
+          field = fieldVisitor.visit(field);
+        }
         formatValue(b, field.value(), field.attributes());
         displayComma = i < fieldList.size();
       }

api/src/test/java/com/tersesystems/echopraxia/api/ToStringFormatTests.java

@@ -1,8 +1,11 @@
 package com.tersesystems.echopraxia.api;
 
+import static com.tersesystems.echopraxia.api.Value.array;
+import static com.tersesystems.echopraxia.api.Value.string;
 import static org.assertj.core.api.Assertions.assertThat;
 
 import java.time.Duration;
+import java.util.*;
 import org.jetbrains.annotations.NotNull;
 import org.junit.jupiter.api.Test;
 
@@ -17,21 +20,71 @@ public void testSimpleFormat() {
     assertThat(field.value().asString().raw()).isEqualTo("PT24H");
   }
 
+  @Test
+  public void testNestedSimpleFormat() {
+    MyFieldBuilder fb = MyFieldBuilder.instance();
+
+    Field nameField = fb.string("name", "event name");
+    Field durationField = fb.duration("duration", Duration.ofDays(1));
+    Field eventField = fb.keyValue("event", Value.object(nameField, durationField));
+
+    var s = eventField.toString();
+    assertThat(s).isEqualTo("event={name=event name, duration=1 day}");
+  }
+
+  @Test
+  public void testArraySimpleFormat() {
+    MyFieldBuilder fb = MyFieldBuilder.instance();
+
+    Duration[] durationsArray = {Duration.ofDays(1), Duration.ofDays(2)};
+    var visitor =
+        new SimpleFieldVisitor() {
+          @Override
+          public @NotNull ArrayVisitor visitArray() {
+            return new SimpleArrayVisitor() {
+              @Override
+              public @NotNull Field done() {
+                return fieldCreator.create(
+                    name, array(f -> string(formatDuration(f)), durationsArray), attributes);
+              }
+            };
+          }
+        };
+
+    var durationsField =
+        fb.array("durations", array(f -> string(f.toString()), durationsArray))
+            .withToStringFormat(visitor);
+    var s = durationsField.toString();
+    assertThat(s).isEqualTo("durations=[1 day, 2 days]");
+  }
+
   static class MyFieldBuilder implements PresentationFieldBuilder {
     static MyFieldBuilder instance() {
       return new MyFieldBuilder();
     }
 
     public PresentationField duration(String name, Duration duration) {
       return string(name, duration.toString())
-          .asValueOnly()
           .withToStringFormat(
               new SimpleFieldVisitor() {
                 @Override
                 public @NotNull Field visitString(@NotNull Value<String> stringValue) {
-                  return string(name, duration.toDays() + " day");
+                  return string(name, formatDuration(duration));
                 }
               });
     }
   }
+
+  private static String formatDuration(Duration duration) {
+    List<String> parts = new ArrayList<>();
+    long days = duration.toDaysPart();
+    if (days > 0) {
+      parts.add(plural(days, "day"));
+    }
+    return String.join(", ", parts);
+  }
+
+  private static String plural(long num, String unit) {
+    return num + " " + unit + (num == 1 ? "" : "s");
+  }
 }