SPIGOT-4441: Fix serializing Components to and from Legacy

While cfeef75cd9 might of semi helped being able to save black text
lore, it actually took a fundamental problem with the legacy serialization
code and expanded it to break even more aspects of the server when dealing
with Component to Legacy conversion.

This is causing data loss in Spigot with cases such as setting an item name
to white gets stripped resulting in it being italic.

Additionally, things such as book pages have been returning black formatting
codes for the end of the line even when the user doesn't have colors in the book.

The root issue is that the "Default Color" system is fundamentally wrong.

Components do not and should not care about what element of the game they
are being used by, and that's what the default color system did.

It results in components that if obtained from 1 source such as a Book
where the default / rendered color is black, is then copied to another
source such as an Entity name, the black is carried forward and shown
in the Entity name, when in reality it should have been white.

This commit reverts cfeef75cd9 and fixes the underlying serialization
issues when it comes to Legacy to and From conversions.

There was quite a number of issues with this code overall, in how
it handles inserting color codes, new line parsing and such.

Books was using mojangs own "getLegacyString" which doesn't match behavior.
We also do not want to use Mojangs method as there is no guarantee they don't
remove that in future.
Plus, everything about books uses the CB implementation anyways, and it should
be consistent (this was mandatory to avoid serialization format changes on old vs new)

These changes as is results in Item Stacks already serialized will not
change contents when they go to component and back, so this won't impact
any existing data.

Newly created books though for example will change behavior in that they
will no longer insert black color codes in the serialized data and will
only represent intentional color changes by the creator of the book.
This will result in cleaner data on them, and books are the only thing
I'm aware of that has a behavioral shift due to the likelyhood of the
default color system kicking in on other parts of the string.

A unit test has been added to verify integrity of serialization to
ensure that any legacy string that is converted into Components will
always re-encode back in the same way when going back to Legacy.

nms-patches/PlayerConnection.patch

@@ -133,7 +133,7 @@
 +    // CraftBukkit start
 +    @Deprecated
      public void disconnect(IChatBaseComponent ichatbasecomponent) {
-+        disconnect(CraftChatMessage.fromComponent(ichatbasecomponent, EnumChatFormat.WHITE));
++        disconnect(CraftChatMessage.fromComponent(ichatbasecomponent));
 +    }
 +    // CraftBukkit end
 +

src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java

@@ -135,7 +135,6 @@ import net.minecraft.server.EntityWolf;
 import net.minecraft.server.EntityZombie;
 import net.minecraft.server.EntityZombieHusk;
 import net.minecraft.server.EntityZombieVillager;
-import net.minecraft.server.EnumChatFormat;
 import net.minecraft.server.IChatBaseComponent;
 import net.minecraft.server.NBTTagCompound;
 import org.bukkit.EntityEffect;
@@ -782,7 +781,7 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
 
     @Override
     public String getName() {
-        return CraftChatMessage.fromComponent(getHandle().getDisplayName(), EnumChatFormat.WHITE);
+        return CraftChatMessage.fromComponent(getHandle().getDisplayName());
     }
 
     @Override

src/main/java/org/bukkit/craftbukkit/entity/CraftPlayer.java

@@ -35,7 +35,6 @@ import net.minecraft.server.Container;
 import net.minecraft.server.Entity;
 import net.minecraft.server.EntityLiving;
 import net.minecraft.server.EntityPlayer;
-import net.minecraft.server.EnumChatFormat;
 import net.minecraft.server.EnumColor;
 import net.minecraft.server.EnumGamemode;
 import net.minecraft.server.IChatBaseComponent;
@@ -220,7 +219,7 @@ public class CraftPlayer extends CraftHumanEntity implements Player {
 
     @Override
     public String getPlayerListName() {
-        return getHandle().listName == null ? getName() : CraftChatMessage.fromComponent(getHandle().listName, EnumChatFormat.WHITE);
+        return getHandle().listName == null ? getName() : CraftChatMessage.fromComponent(getHandle().listName);
     }
 
     @Override

src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaBook.java

@@ -127,7 +127,7 @@ public class CraftMetaBook extends CraftMetaItem implements BookMeta {
             if (hasPages()) {
                 NBTTagList list = new NBTTagList();
                 for (IChatBaseComponent page : pages) {
-                    list.add(NBTTagString.a(page == null ? "" : page.getLegacyString()));
+                    list.add(NBTTagString.a(page == null ? "" : CraftChatMessage.fromComponent(page)));
                 }
                 itemData.set(BOOK_PAGES.NBT, list);
             }

src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaItem.java

@@ -37,7 +37,6 @@ import java.util.logging.Logger;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import net.minecraft.server.ChatComponentText;
-import net.minecraft.server.EnumChatFormat;
 import net.minecraft.server.EnumItemSlot;
 import net.minecraft.server.GenericAttributes;
 import net.minecraft.server.IChatBaseComponent;
@@ -675,7 +674,7 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable, BlockDataMeta {
         NBTTagList tagList = new NBTTagList();
         for (IChatBaseComponent value : list) {
             // SPIGOT-5342 - horrible hack as 0 version does not go through the Mojang updater
-            tagList.add(NBTTagString.a(version <= 0 || version >= 1803 ? CraftChatMessage.toJSON(value) : CraftChatMessage.fromComponent(value, EnumChatFormat.DARK_PURPLE))); // SPIGOT-4935
+            tagList.add(NBTTagString.a(version <= 0 || version >= 1803 ? CraftChatMessage.toJSON(value) : CraftChatMessage.fromComponent(value))); // SPIGOT-4935
         }
 
         return tagList;
@@ -755,7 +754,7 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable, BlockDataMeta {
 
     @Override
     public String getDisplayName() {
-        return CraftChatMessage.fromComponent(displayName, EnumChatFormat.WHITE);
+        return CraftChatMessage.fromComponent(displayName);
     }
 
     @Override
@@ -770,7 +769,7 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable, BlockDataMeta {
 
     @Override
     public String getLocalizedName() {
-        return CraftChatMessage.fromComponent(locName, EnumChatFormat.WHITE);
+        return CraftChatMessage.fromComponent(locName);
     }
 
     @Override
@@ -883,7 +882,7 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable, BlockDataMeta {
 
     @Override
     public List<String> getLore() {
-        return this.lore == null ? null : new ArrayList<String>(Lists.transform(this.lore, (line) -> CraftChatMessage.fromComponent(line, EnumChatFormat.DARK_PURPLE)));
+        return this.lore == null ? null : new ArrayList<String>(Lists.transform(this.lore, CraftChatMessage::fromComponent));
     }
 
     @Override
@@ -1219,14 +1218,14 @@ class CraftMetaItem implements ItemMeta, Damageable, Repairable, BlockDataMeta {
     @Overridden
     ImmutableMap.Builder<String, Object> serialize(ImmutableMap.Builder<String, Object> builder) {
         if (hasDisplayName()) {
-            builder.put(NAME.BUKKIT, CraftChatMessage.fromComponent(displayName, EnumChatFormat.WHITE));
+            builder.put(NAME.BUKKIT, CraftChatMessage.fromComponent(displayName));
         }
         if (hasLocalizedName()) {
-            builder.put(LOCNAME.BUKKIT, CraftChatMessage.fromComponent(locName, EnumChatFormat.WHITE));
+            builder.put(LOCNAME.BUKKIT, CraftChatMessage.fromComponent(locName));
         }
 
         if (hasLore()) {
-            builder.put(LORE.BUKKIT, ImmutableList.copyOf(Lists.transform(lore, (line) -> CraftChatMessage.fromComponent(line, EnumChatFormat.DARK_PURPLE))));
+            builder.put(LORE.BUKKIT, ImmutableList.copyOf(Lists.transform(lore, CraftChatMessage::fromComponent)));
         }
 
         if (hasCustomModelData()) {

src/main/java/org/bukkit/craftbukkit/util/CraftChatMessage.java

@@ -38,7 +38,9 @@ public final class CraftChatMessage {
     }
 
     private static final class StringMessage {
-        private static final Pattern INCREMENTAL_PATTERN = Pattern.compile("(" + String.valueOf(org.bukkit.ChatColor.COLOR_CHAR) + "[0-9a-fk-or])|(\\n)|((?:(?:https?):\\/\\/)?(?:[-\\w_\\.]{2,}\\.[a-z]{2,4}.*?(?=[\\.\\?!,;:]?(?:[" + String.valueOf(org.bukkit.ChatColor.COLOR_CHAR) + " \\n]|$))))", Pattern.CASE_INSENSITIVE);
+        private static final Pattern INCREMENTAL_PATTERN = Pattern.compile("(" + String.valueOf(org.bukkit.ChatColor.COLOR_CHAR) + "[0-9a-fk-or])|((?:(?:https?):\\/\\/)?(?:[-\\w_\\.]{2,}\\.[a-z]{2,4}.*?(?=[\\.\\?!,;:]?(?:[" + String.valueOf(org.bukkit.ChatColor.COLOR_CHAR) + " \\n]|$))))|(\\n)", Pattern.CASE_INSENSITIVE);
+        // Separate pattern with no group 3, new lines are part of previous string
+        private static final Pattern INCREMENTAL_PATTERN_KEEP_NEWLINES = Pattern.compile("(" + String.valueOf(org.bukkit.ChatColor.COLOR_CHAR) + "[0-9a-fk-or])|((?:(?:https?):\\/\\/)?(?:[-\\w_\\.]{2,}\\.[a-z]{2,4}.*?(?=[\\.\\?!,;:]?(?:[" + String.valueOf(org.bukkit.ChatColor.COLOR_CHAR) + " ]|$))))", Pattern.CASE_INSENSITIVE);
 
         private final List<IChatBaseComponent> list = new ArrayList<IChatBaseComponent>();
         private IChatBaseComponent currentChatComponent = new ChatComponentText("");
@@ -55,20 +57,23 @@ public final class CraftChatMessage {
             }
             list.add(currentChatComponent);
 
-            Matcher matcher = INCREMENTAL_PATTERN.matcher(message);
+            Matcher matcher = (keepNewlines ? INCREMENTAL_PATTERN_KEEP_NEWLINES : INCREMENTAL_PATTERN).matcher(message);
             String match = null;
+            boolean needsAdd = false;
             while (matcher.find()) {
                 int groupId = 0;
                 while ((match = matcher.group(++groupId)) == null) {
                     // NOOP
                 }
-                appendNewComponent(matcher.start(groupId));
+                int index = matcher.start(groupId);
+                if (index > currentIndex) {
+                    needsAdd = false;
+                    appendNewComponent(index);
+                }
                 switch (groupId) {
                 case 1:
                     EnumChatFormat format = formatMap.get(match.toLowerCase(java.util.Locale.ENGLISH).charAt(1));
-                    if (format == EnumChatFormat.RESET) {
-                        modifier = new ChatModifier();
-                    } else if (format.isFormat()) {
+                    if (format.isFormat() && format != EnumChatFormat.RESET) {
                         switch (format) {
                         case BOLD:
                             modifier.setBold(Boolean.TRUE);
@@ -91,26 +96,27 @@ public final class CraftChatMessage {
                     } else { // Color resets formatting
                         modifier = new ChatModifier().setColor(format);
                     }
+                    needsAdd = true;
                     break;
                 case 2:
-                    if (keepNewlines) {
-                        currentChatComponent.addSibling(new ChatComponentText("\n"));
-                    } else {
-                        currentChatComponent = null;
-                    }
-                    break;
-                case 3:
                     if (!(match.startsWith("http://") || match.startsWith("https://"))) {
                         match = "http://" + match;
                     }
                     modifier.setChatClickable(new ChatClickable(EnumClickAction.OPEN_URL, match));
                     appendNewComponent(matcher.end(groupId));
                     modifier.setChatClickable((ChatClickable) null);
+                    break;
+                case 3:
+                    if (needsAdd) {
+                        appendNewComponent(index);
+                    }
+                    currentChatComponent = null;
+                    break;
                 }
                 currentIndex = matcher.end(groupId);
             }
 
-            if (currentIndex < message.length()) {
+            if (currentIndex < message.length() || needsAdd) {
                 appendNewComponent(message.length());
             }
 
@@ -118,12 +124,12 @@ public final class CraftChatMessage {
         }
 
         private void appendNewComponent(int index) {
-            if (index <= currentIndex) {
-                return;
-            }
             IChatBaseComponent addition = new ChatComponentText(message.substring(currentIndex, index)).setChatModifier(modifier);
             currentIndex = index;
             modifier = modifier.clone();
+            if (modifier.getColor() == EnumChatFormat.RESET) {
+                modifier.setColor(null);
+            }
             if (currentChatComponent == null) {
                 currentChatComponent = new ChatComponentText("");
                 list.add(currentChatComponent);
@@ -160,21 +166,29 @@ public final class CraftChatMessage {
         return new StringMessage(message, keepNewlines).getOutput();
     }
 
-    public static String fromComponent(IChatBaseComponent component) {
-        return fromComponent(component, EnumChatFormat.BLACK);
-    }
-
     public static String toJSON(IChatBaseComponent component) {
         return IChatBaseComponent.ChatSerializer.a(component);
     }
 
-    public static String fromComponent(IChatBaseComponent component, EnumChatFormat defaultColor) {
+    public static String fromComponent(IChatBaseComponent component) {
         if (component == null) return "";
         StringBuilder out = new StringBuilder();
 
-        for (IChatBaseComponent c : (Iterable<IChatBaseComponent>) component) {
+        boolean hadFormat = false;
+        for (IChatBaseComponent c : component) {
             ChatModifier modi = c.getChatModifier();
-            out.append(modi.getColor() == null ? defaultColor : modi.getColor());
+            EnumChatFormat color = modi.getColor();
+            if (!c.getText().isEmpty() || color != null) {
+                if (color != null) {
+                    out.append(color);
+                    if (color != EnumChatFormat.RESET) {
+                        hadFormat = true;
+                    }
+                } else if (hadFormat) {
+                    out.append(ChatColor.RESET);
+                    hadFormat = false;
+                }
+            }
             if (modi.isBold()) {
                 out.append(EnumChatFormat.BOLD);
             }
@@ -192,7 +206,7 @@ public final class CraftChatMessage {
             }
             out.append(c.getText());
         }
-        return out.toString().replaceFirst("^(" + defaultColor + ")*", "");
+        return out.toString();
     }
 
     public static IChatBaseComponent fixComponent(IChatBaseComponent component) {

src/test/java/org/bukkit/craftbukkit/util/CraftChatMessageTest.java

@@ -0,0 +1,89 @@
+package org.bukkit.craftbukkit.util;
+
+import net.minecraft.server.IChatBaseComponent;
+import org.bukkit.support.AbstractTestingBase;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class CraftChatMessageTest extends AbstractTestingBase {
+
+    @Test
+    public void testSimpleStrings() {
+        // These should be able to go from legacy to comp to legacy back without data changing
+        testString("§fFoo");
+        testString("§fFoo§f§l"); // Keeps empty format at end
+        testString("Foo");
+        testString("§r§oFoo"); // Retains reset at start (item names can use this to get rid of italics)
+        testString("Foo§bBar");
+        testString("F§loo§b§oBa§b§lr"); // any non color formatting code implies previous color code.
+        // So §l at start has no inherited color code, so that's fine, but the one at the end,
+        // while Ba§l would work visually, serializing back will include the implied color
+
+        testString("F§loo§rBa§lr"); // But if reset was used before.... then it can be standalone
+        testString("§fFoo§bBar");
+        testString("§fFoo§bBar§rBaz");
+    }
+
+    @Test
+    public void testNewLineBehavior() {
+        // new line retain should stay as 1 comp
+        testString("Hello§0\n§rFoo\n§5Test", true);
+        testString("§0Foo!\n",  true);
+        testString("§0Foo!§0\\n§0\\n§0Bar\n", true);
+
+        // dont retain line returns multiple components
+        IChatBaseComponent[] components = CraftChatMessage.fromString("Hello§0\n§rFoo\n§5Test");
+        assertEquals("Has 3 components", 3, components.length);
+        assertEquals("Hello§0", CraftChatMessage.fromComponent(components[0]));
+        assertEquals("§rFoo",   CraftChatMessage.fromComponent(components[1]));
+        assertEquals("§5Test",  CraftChatMessage.fromComponent(components[2]));
+    }
+
+    @Test
+    public void testComponents() {
+        testComponent("Foo§bBar§rBaz",   create("Foo", "§bBar", "Baz"));
+        testComponent("§fFoo§bBar§rBaz", create("", "§fFoo", "§bBar", "Baz"));
+        testComponent("§fFoo§bBar§rBaz", create("", "§fFoo", "§bBar", "", "Baz"));
+        testComponent("§fFoo§bBar§rBaz", create("§fFoo", "§bBar", "Baz"));
+        testComponent("Foo§bBar§rBaz",   create("", "Foo", "§bBar", "Baz"));
+        testComponent("§fFoo§bBar§rBaz", create("§fFoo", "§bBar", "Baz"));
+        testComponent("F§foo§bBar§rBaz", create("F§foo", "§bBar", "Baz"));
+    }
+
+    private IChatBaseComponent create(String txt, String ...rest) {
+        IChatBaseComponent cmp = CraftChatMessage.fromString(txt, false)[0];
+        for (String s : rest) {
+            cmp.addSibling(CraftChatMessage.fromString(s, true)[0]);
+        }
+
+        return cmp;
+    }
+
+    private void testString(String expected) {
+        testString(expected, false);
+    }
+
+    private void testString(String expected, boolean keepNewLines) {
+        testString(expected, expected, keepNewLines);
+    }
+
+    private void testString(String input, String expected) {
+        testString(input, expected, false);
+    }
+
+    private void testString(String input, String expected, boolean keepNewLines) {
+        IChatBaseComponent cmp = CraftChatMessage.fromString(input, keepNewLines)[0];
+        String actual = CraftChatMessage.fromComponent(cmp);
+        assertEquals("\nComponent: " + cmp + "\n", expected, actual);
+    }
+
+    private void testComponent(String expected, IChatBaseComponent cmp) {
+        String actual = CraftChatMessage.fromComponent(cmp);
+        assertEquals("\nComponent: " + cmp + "\n", expected, actual);
+
+        IChatBaseComponent expectedCmp = CraftChatMessage.fromString(expected, true)[0];
+        String actualExpectedCmp = CraftChatMessage.fromComponent(expectedCmp);
+        assertEquals("\nComponent: " + expectedCmp + "\n", expected, actualExpectedCmp);
+    }
+}