api: Add methods to join components using a collector

api/src/main/java/net/kyori/adventure/text/AbstractComponentBuilder.java

@@ -209,6 +209,11 @@ private void prepareChildren() {
     return (B) this;
   }
 
+  @Override
+  public @NonNull List<Component> children() {
+    return Collections.unmodifiableList(this.children);
+  }
+
   @Override
   @SuppressWarnings("unchecked")
   public @NonNull B style(final @NonNull Style style) {

api/src/main/java/net/kyori/adventure/text/Component.java

@@ -33,6 +33,7 @@
 import java.util.function.Function;
 import java.util.function.UnaryOperator;
 import java.util.regex.Pattern;
+import java.util.stream.Collector;
 import net.kyori.adventure.key.Key;
 import net.kyori.adventure.text.event.ClickEvent;
 import net.kyori.adventure.text.event.HoverEvent;
@@ -159,6 +160,44 @@ public interface Component extends ComponentBuilderApplicable, ComponentLike, Ex
     return builder.build();
   }
 
+  /**
+   * Create a collector that will join components without a separator.
+   *
+   * @return a collector that can join components
+   * @since 4.6.0
+   */
+  static @NonNull Collector<Component, ? extends ComponentBuilder<?, ?>, Component> toComponent() {
+    return toComponent(Component.empty());
+  }
+
+  /**
+   * Create a collector that will join components using the provided separator.
+   *
+   * @param separator the separator to join with
+   * @return a collector that can join components
+   * @since 4.6.0
+   */
+  static @NonNull Collector<Component, ? extends ComponentBuilder<?, ?>, Component> toComponent(final @NonNull Component separator) {
+    return Collector.of(
+      Component::text,
+      (builder, add) -> {
+        if(separator != Component.empty() && !builder.children().isEmpty()) {
+          builder.append(separator);
+        }
+        builder.append(add);
+      }, (a, b) -> {
+        final List<Component> aChildren = a.children();
+        final TextComponent.Builder ret = Component.text().append(aChildren);
+        if(!aChildren.isEmpty()) {
+          ret.append(separator);
+        }
+        ret.append(b.children());
+        return ret;
+      },
+      TextComponent.Builder::build
+    );
+  }
+
   /*
    * ---------------------------
    * ---- BlockNBTComponent ----

api/src/main/java/net/kyori/adventure/text/ComponentBuilder.java

@@ -23,6 +23,7 @@
  */
 package net.kyori.adventure.text;
 
+import java.util.List;
 import java.util.Set;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -155,6 +156,14 @@ public interface ComponentBuilder<C extends BuildableComponent<C, B>, B extends
   @Contract("_ -> this")
   @NonNull B mapChildrenDeep(final @NonNull Function<BuildableComponent<?, ?>, ? extends BuildableComponent<?, ?>> function);
 
+  /**
+   * Get an unmodifiable list containing all children currently in this builder.
+   *
+   * @return the list of children
+   * @since 4.6.0
+   */
+  @NonNull List<Component> children();
+
   /**
    * Sets the style.
    *

api/src/test/java/net/kyori/adventure/text/AbstractComponentTest.java

@@ -29,6 +29,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.stream.Stream;
 import net.kyori.adventure.text.event.ClickEvent;
 import net.kyori.adventure.text.event.HoverEvent;
 import net.kyori.adventure.text.format.NamedTextColor;
@@ -376,4 +377,39 @@ void testBuilderApplyDeep() {
     assertThat(children).hasSize(2);
     forEachTransformAndAssert(children, Component::color, color -> assertEquals(NamedTextColor.GREEN, color));
   }
+
+  @Test
+  void testCollectorNoSeparator() {
+    final Component joined = Stream.of(
+      Component.text("Hello", NamedTextColor.RED),
+      Component.text("World")
+    ).collect(Component.toComponent());
+    final Component expected = Component.text()
+      .append(Component.text("Hello", NamedTextColor.RED))
+      .append(Component.text("World"))
+      .build();
+
+    assertEquals(expected, joined);
+  }
+
+  @Test
+  void testCollectorWithSeparator() {
+    final Component joined = Stream.of(
+      Component.text("Hello", NamedTextColor.RED),
+      Component.text("World")
+    ).collect(Component.toComponent(Component.space()));
+
+    final Component expected = Component.text()
+      .append(Component.text("Hello", NamedTextColor.RED))
+      .append(Component.space())
+      .append(Component.text("World"))
+      .build();
+
+    assertEquals(expected, joined);
+  }
+
+  @Test
+  void testCollectOnEmptyStreamReturnsEmptyComponent() {
+    assertEquals(Component.empty(), Stream.<Component>of().collect(Component.toComponent()));
+  }
 }