fix(emoji): render a standard emoji for the reaction endpoints

src/Rest/Helpers/Emoji/EmojiBuilder.php

@@ -73,10 +73,25 @@ public function get(): array
         return $this->data;
     }
 
+    /**
+     * The emoji as a reaction endpoint takes it.
+     *
+     * A custom emoji is "name:id". A standard one is the character itself,
+     * percent encoded, and may be held under either key: fromPart() puts it in
+     * name, because that is where Discord sends it in a reaction event, while
+     * setId() has long been the documented way to write one by hand.
+     *
+     * @see https://discord.com/developers/docs/resources/channel#create-reaction
+     */
     public function __toString(): string
     {
-        return isset($this->data['name'])
-            ? $this->data['name'] . ':' . $this->data['id']
-            : urlencode($this->data['id']);
+        $id = $this->data['id'] ?? null;
+        $name = $this->data['name'] ?? null;
+
+        if ($id !== null && $name !== null) {
+            return $name . ':' . $id;
+        }
+
+        return rawurlencode((string) ($name ?? $id));
     }
 }

tests/Rest/Helpers/Emoji/EmojiBuilderTest.php

@@ -53,6 +53,38 @@ public function testCreateEmojiFromIdAndName(): void
         $this->assertEquals('name:12345', (string) $emojiBuilder);
     }
 
+    /**
+     * A reaction event carries a standard emoji as its name with no id, which
+     * is what fromPart() copies across. Rendering that as "✅:" — with the id
+     * missing entirely — made every reaction on a standard emoji a malformed
+     * request, and warned about an undefined key on the way out.
+     */
+    public function testCreateEmojiFromNameAlone(): void
+    {
+        $emojiBuilder = new EmojiBuilder();
+        $emojiBuilder->setName('✅');
+
+        $this->assertEquals(rawurlencode('✅'), (string) $emojiBuilder);
+    }
+
+    public function testAStandardEmojiFromAReactionEventIsRenderedForTheEndpoint(): void
+    {
+        $emoji = new Emoji();
+        $emoji->name = '❌';
+        $emoji->id = null;
+
+        $this->assertEquals(rawurlencode('❌'), (string) EmojiBuilder::fromPart($emoji));
+    }
+
+    public function testACustomEmojiFromAReactionEventKeepsBothHalves(): void
+    {
+        $emoji = new Emoji();
+        $emoji->name = 'apex';
+        $emoji->id = '12345';
+
+        $this->assertEquals('apex:12345', (string) EmojiBuilder::fromPart($emoji));
+    }
+
     #[DataProvider('getFromPartProvider')]
     public function testGetFromPart(Emoji $emoji, array $result): void
     {