Added documents about @fedify/lint

Author: 2chanhaeng

AGENTS.md

@@ -77,6 +77,7 @@ The repository is organized as a monorepo with the following packages:
  -  *packages/koa/*: Koa integration (@fedify/koa)
  -  *packages/postgres/*: PostgreSQL drivers (@fedify/postgres)
  -  *packages/redis/*: Redis drivers (@fedify/redis)
+ -  *packages/lint/*: Linting utilities (@fedify/lint)
  -  *packages/nestjs/*: NestJS integration (@fedify/nestjs)
  -  *packages/next/*: Next.js integration (@fedify/next)
  -  *packages/sqlite/*: SQLite driver (@fedify/sqlite)

CHANGES.md

@@ -186,6 +186,13 @@ To be released.
      -  This package is primarily used by generated vocabulary classes and
         provides the runtime infrastructure for ActivityPub object processing.
 
+### @fedify/lint
+
+ -  Created Fedify linting tools as the *@fedify/lint* package.
+    This package provides shared Deno Lint and ESLint configurations for
+    consistent code style across Fedify packages and user projects. 
+    [[#297], [#494] by ChanHaeng Lee]
+
 
 Version 1.10.0
 --------------

docs/tutorial/basics.md

@@ -1279,6 +1279,128 @@ should see the actor's followers in the bulleted list.
 [Hono]: https://hono.dev/
 
 
+Linting your federation code
+-----------------------------
+
+As your federated server grows, it's important to maintain code quality and
+catch common mistakes early.  Fedify provides linting plugins for both
+[Deno Lint] and [ESLint], which include specialized linting rules for
+federation code.
+
+The `@fedify/lint` package helps you avoid common pitfalls such as:
+
+ -  Using incorrect actor IDs (e.g., relative URLs instead of
+    `Context.getActorUri()`)
+ -  Missing required actor properties (inbox, outbox, followers, etc.)
+ -  Incorrect URL patterns for actor collections
+ -  Missing public keys or assertion methods
+
+### Using Deno Lint
+
+If you are using Deno, you can use the Deno Lint plugin.  First, install the
+plugin:
+
+~~~~ sh
+deno add jsr:@fedify/lint
+~~~~
+
+Then add the plugin to your *deno.json* configuration file:
+
+~~~~ json
+{
+  "lint": {
+    "plugins": ["jsr:@fedify/lint"]
+  }
+}
+~~~~
+
+Now you can run the linter on your code:
+
+~~~~ sh
+deno lint
+~~~~
+
+### Using ESLint
+
+For ESLint users (including Deno, Bun, and Node.js), first install the plugin:
+
+::: code-group
+
+~~~~ sh [Bun]
+bun add -D @fedify/lint eslint
+~~~~
+
+~~~~ sh [Node.js]
+npm add -D @fedify/lint eslint
+~~~~
+
+:::
+
+Then create an ESLint configuration file (e.g., *eslint.config.ts*) in your
+project directory:
+
+~~~~ typescript twoslash
+import fedifyLint from "@fedify/lint";
+
+export default [{
+  ...fedifyLint,
+  files: ["**/*.ts"],
+}];
+~~~~
+
+Now you can run the linter on your code:
+
+::: code-group
+
+~~~~ sh [Bun]
+bun run eslint .
+~~~~
+
+~~~~ sh [Node.js]
+npx eslint .
+~~~~
+
+:::
+
+> [!NOTE]
+> When using ESLint with Deno, you may need to exclude some Deno-specific
+> lint rules like `no-unused-vars` to avoid conflicts.
+
+### Example
+
+For example, if you had written the actor dispatcher like this:
+
+~~~~ typescript
+// ❌ Wrong: Using relative URL
+federation.setActorDispatcher(
+  "/{identifier}",
+  (_ctx, identifier) => {
+    return new Person({
+      id: new URL(`/${identifier}`),  // ❌ Linter will catch this
+      name: "Example User",
+    });
+  },
+);
+~~~~
+
+The linter would warn you:
+
+~~~~
+error[fedify-lint/actor-id-mismatch]: Actor's `id` property must match
+`_ctx.getActorUri(identifier)`. Ensure you're using the correct context method.
+~~~~
+
+This helps you catch mistakes before they cause issues in production.  The
+linter includes many other rules to ensure your federation code follows best
+practices.
+
+For more information about available rules and configuration options, see
+the [`@fedify/lint` documentation](https://jsr.io/@fedify/lint).
+
+[Deno Lint]: https://docs.deno.com/runtime/reference/lint_plugins/
+[ESLint]: https://eslint.org/
+
+
 Wrapping up
 -----------