fix(web): highlight Scala code blocks (#958)

Co-authored-by: Rinat S <rinat.suleimanov@jetbrains.com>

Author: dajiaohuang

apps/web/src/lib/highlighter.test.ts

@@ -1,11 +1,32 @@
 import { expect, test } from "bun:test";
-import { SHIKI_FILE_LANGUAGES } from "./highlighter";
+import { createJavaScriptRegexEngine } from "shiki/engine/javascript";
+import {
+	chatShikiLanguageId,
+	createChatHighlighter,
+	SHIKI_FILE_LANGUAGES,
+	shikiLanguageId,
+} from "./highlighter";
 
 test("the Monaco Shiki language registration list has no duplicate ids", () => {
 	const ids = SHIKI_FILE_LANGUAGES.map((language) => language.id);
 	expect(new Set(ids).size).toBe(ids.length);
 });
 
+test("Scala is recognized for chat fences and Scala files", () => {
+	const scala = SHIKI_FILE_LANGUAGES.find((language) => language.id === "scala");
+	expect(scala?.extensions).toContain(".scala");
+	expect(scala?.chat).toBe(true);
+	expect(shikiLanguageId("Scala")).toBe("scala");
+	expect(chatShikiLanguageId("scala")).toBe("scala");
+});
+
+test("a Scala chat fence renders with Shiki tokens", async () => {
+	const highlight = createChatHighlighter(createJavaScriptRegexEngine);
+	const html = await highlight('object Greeting { val message: String = "hello" }', "scala");
+	expect(html).not.toBeNull();
+	expect(html).toContain("<span");
+});
+
 test("every Monaco language id is supplied by its Shiki grammar", async () => {
 	const modules = await Promise.all(SHIKI_FILE_LANGUAGES.map((language) => language.load()));
 	for (const [index, language] of SHIKI_FILE_LANGUAGES.entries()) {

apps/web/src/lib/highlighter.ts

@@ -139,6 +139,13 @@ export const SHIKI_FILE_LANGUAGES: readonly ShikiFileLanguage[] = [
 		aliases: ["Kotlin", "kt", "kts"],
 		load: () => import("@shikijs/langs/kotlin"),
 	},
+	{
+		id: "scala",
+		extensions: [".scala"],
+		aliases: ["Scala"],
+		chat: true,
+		load: () => import("@shikijs/langs/scala"),
+	},
 	{
 		id: "swift",
 		extensions: [".swift"],