Add Dart syntax highlighting (#1326)

packages/highlight/src/__tests__/highlighter.test.ts

@@ -46,6 +46,22 @@ describe("highlightCode", () => {
     expect(stringToken?.style).toBe("string");
   });
 
+  it("highlights Dart code", () => {
+    const code = 'class Greeter {\n  final String message = "hello";\n}';
+    const result = highlightCode(code, "test.dart");
+
+    expect(result).toHaveLength(3);
+
+    const classToken = result[0].find((t) => t.text === "class");
+    expect(classToken?.style).toBe("keyword");
+
+    const finalToken = result[1].find((t) => t.text === "final");
+    expect(finalToken?.style).toBe("keyword");
+
+    const stringToken = result[1].find((t) => t.text.includes("hello"));
+    expect(stringToken?.style).toBe("string");
+  });
+
   it("highlights TSX code with correct dialect", () => {
     const code = 'const el = <div className="test">hello</div>;';
     const result = highlightCode(code, "test.tsx");

packages/highlight/src/__tests__/parsers.test.ts

@@ -14,6 +14,7 @@ describe("isLanguageSupported", () => {
     expect(isLanguageSupported("test.html")).toBe(true);
     expect(isLanguageSupported("test.java")).toBe(true);
     expect(isLanguageSupported("test.swift")).toBe(true);
+    expect(isLanguageSupported("test.dart")).toBe(true);
     expect(isLanguageSupported("test.ex")).toBe(true);
   });
 
@@ -51,6 +52,7 @@ describe("getSupportedExtensions", () => {
     expect(extensions).toContain("go");
     expect(extensions).toContain("rs");
     expect(extensions).toContain("swift");
+    expect(extensions).toContain("dart");
     expect(extensions).toContain("json");
   });
 });

packages/highlight/src/parsers.ts

@@ -1,4 +1,5 @@
 import { StreamLanguage } from "@codemirror/language";
+import { dart } from "@codemirror/legacy-modes/mode/clike";
 import { swift } from "@codemirror/legacy-modes/mode/swift";
 import { parser as jsParser } from "@lezer/javascript";
 import { parser as jsonParser } from "@lezer/json";
@@ -59,6 +60,8 @@ const parsersByExtension: Record<string, Parser> = {
   rs: rustParser,
   // Swift
   swift: StreamLanguage.define(swift).parser,
+  // Dart
+  dart: StreamLanguage.define(dart).parser,
   // Elixir
   ex: elixirParser,
   exs: elixirParser,