refactor: use get guild role endpoint (#10443)

* refactor: use get guild role endpoint

* style: import order

---------

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

packages/core/src/api/guild.ts

@@ -28,6 +28,7 @@ import {
 	type RESTGetAPIGuildPruneCountResult,
 	type RESTGetAPIGuildQuery,
 	type RESTGetAPIGuildResult,
+	type RESTGetAPIGuildRoleResult,
 	type RESTGetAPIGuildRolesResult,
 	type RESTGetAPIGuildScheduledEventQuery,
 	type RESTGetAPIGuildScheduledEventResult,
@@ -397,6 +398,18 @@ export class GuildsAPI {
 		return this.rest.get(Routes.guildRoles(guildId), { signal }) as Promise<RESTGetAPIGuildRolesResult>;
 	}
 
+	/**
+	 * Get a role in a guild
+	 *
+	 * @see {@link https://discord.com/developers/docs/resources/guild#get-guild-role}
+	 * @param guildId - The id of the guild to fetch the role from
+	 * @param roleId - The id of the role to fetch
+	 * @param options - The options for fetching the guild role
+	 */
+	public async getRole(guildId: Snowflake, roleId: Snowflake, { signal }: Pick<RequestData, 'signal'> = {}) {
+		return this.rest.get(Routes.guildRole(guildId, roleId), { signal }) as Promise<RESTGetAPIGuildRoleResult>;
+	}
+
 	/**
 	 * Creates a guild role
 	 *

packages/discord.js/src/managers/RoleManager.js

@@ -2,7 +2,8 @@
 
 const process = require('node:process');
 const { Collection } = require('@discordjs/collection');
-const { Routes } = require('discord-api-types/v10');
+const { DiscordAPIError } = require('@discordjs/rest');
+const { RESTJSONErrorCodes, Routes } = require('discord-api-types/v10');
 const CachedManager = require('./CachedManager');
 const { DiscordjsTypeError, ErrorCodes } = require('../errors');
 const { Role } = require('../structures/Role');
@@ -61,16 +62,29 @@ class RoleManager extends CachedManager {
    *   .catch(console.error);
    */
   async fetch(id, { cache = true, force = false } = {}) {
-    if (id && !force) {
+    if (!id) {
+      const data = await this.client.rest.get(Routes.guildRoles(this.guild.id));
+      const roles = new Collection();
+      for (const role of data) roles.set(role.id, this._add(role, cache));
+      return roles;
+    }
+
+    if (!force) {
       const existing = this.cache.get(id);
       if (existing) return existing;
     }
 
-    // We cannot fetch a single role, as of this commit's date, Discord API throws with 405
-    const data = await this.client.rest.get(Routes.guildRoles(this.guild.id));
-    const roles = new Collection();
-    for (const role of data) roles.set(role.id, this._add(role, cache));
-    return id ? roles.get(id) ?? null : roles;
+    try {
+      const data = await this.client.rest.get(Routes.guildRole(this.guild.id, id));
+      return this._add(data, cache);
+    } catch (error) {
+      // TODO: Remove this catch in the next major version
+      if (error instanceof DiscordAPIError && error.code === RESTJSONErrorCodes.UnknownRole) {
+        return null;
+      }
+
+      throw error;
+    }
   }
 
   /**