feat: add Fresh lint plugin

Author: csvn

deno.json

@@ -3,6 +3,7 @@
   "workspace": [
     "./examples",
     "./init",
+    "./lint",
     "./plugin-tailwindcss",
     "./plugin-tailwindcss-v3",
     "./update",
@@ -13,8 +14,8 @@
   "license": "MIT",
   "exports": {
     ".": "./src/mod.ts",
-    "./runtime": "./src/runtime/shared.ts",
     "./dev": "./src/dev/mod.ts",
+    "./runtime": "./src/runtime/shared.ts",
     "./compat": "./src/compat.ts",
     "./do-not-use": "./src/internals.ts"
   },

init/src/init.ts

@@ -4,6 +4,7 @@ import * as path from "@std/path";
 
 // Keep these as is, as we replace these version in our release script
 const FRESH_VERSION = "2.0.0-alpha.54";
+const FRESH_LINT_VERSION = "0.0.0";
 const FRESH_TAILWIND_VERSION = "0.0.1-alpha.9";
 const PREACT_VERSION = "10.27.0";
 const PREACT_SIGNALS_VERSION = "2.2.1";
@@ -507,13 +508,15 @@ if (Deno.args.includes("build")) {
       update: "deno run -A -r jsr:@fresh/update .",
     },
     lint: {
+      plugins: ["@fresh/lint"],
       rules: {
         tags: ["fresh", "recommended"],
       },
     },
     exclude: ["**/_fresh/*"],
     imports: {
       "fresh": `jsr:@fresh/core@^${FRESH_VERSION}`,
+      "@fresh/lint": `jsr:@fresh/lint@^${FRESH_LINT_VERSION}`,
       "preact": `npm:preact@^${PREACT_VERSION}`,
       "@preact/signals": `npm:@preact/signals@^${PREACT_SIGNALS_VERSION}`,
     } as Record<string, string>,

lint/README.md

@@ -0,0 +1,26 @@
+# Fresh Lint rules
+
+This is a plugin with custom rules specifically for Fresh.
+
+## Usage
+
+1. Install the Fresh lint plugin
+   ```sh
+   deno add jsr:@fresh/lint
+   ```
+2. Configure the plugin in `deno.json`
+   ```json deno.json
+   {
+     "lint": {
+       "plugins": ["@fresh/lint"],
+       "rules": {
+         "include": ["fresh/[lint-rule]"]
+       }
+     }
+   }
+   ```
+3. You can now start linting Fresh code! 🎉
+
+## Rules
+
+TODO: COMING SOON!

lint/deno.json

@@ -0,0 +1,13 @@
+{
+  "name": "@fresh/lint",
+  "version": "0.0.0",
+  "license": "MIT",
+  "exports": "./src/mod.ts",
+  "publish": {
+    "include": [
+      "src/**/*.ts",
+      "deno.json",
+      "README.md"
+    ]
+  }
+}

lint/src/mod.ts

@@ -0,0 +1,28 @@
+import { rules } from "./rules.ts";
+
+/**
+ * Plugin for Fresh linting rules.
+ *
+ * For a full list of rules, see {@linkcode rules}.
+ *
+ * Enable lint rules by updating `deno.json`, each rule
+ * should be prefixed with `fresh/<rule_name>`.
+ *
+ * @example
+ * ```json deno.json
+ * {
+ *   "lint": {
+ *     "plugins": ["@fresh/lint"],
+ *     "rules": {
+ *       "include": ["fresh/test"]
+ *     }
+ *   }
+ * }
+ * ```
+ */
+const plugin: Deno.lint.Plugin = {
+  name: "fresh",
+  rules,
+};
+
+export default plugin;

lint/src/rules.ts

@@ -0,0 +1,5 @@
+import * as test from "./rules/test-rule.ts";
+
+export const rules: Deno.lint.Plugin["rules"] = {
+  [test.RULE_NAME]: test.rule,
+};

lint/src/rules/test-rule.test.ts

@@ -0,0 +1,22 @@
+import { expect } from "@std/expect";
+import { rule, RULE_NAME } from "./test-rule.ts";
+
+const testPlugin: Deno.lint.Plugin = {
+  name: "fresh",
+  rules: { [RULE_NAME]: rule },
+};
+
+Deno.test("fresh/test - disallow 'test' const", () => {
+  const diagnostics = Deno.lint.runPlugin(
+    testPlugin,
+    "main.ts",
+    "const _a = 'a';\n\nconst test = 2;\n",
+  );
+
+  const d = diagnostics[0];
+
+  expect(diagnostics.length).toBe(1);
+  expect(d.id).toBe("fresh/test");
+  expect(d.range).toEqual([23, 27]);
+  expect(d.message).toBe("Do not use 'test' as a variable name.");
+});

lint/src/rules/test-rule.ts

@@ -0,0 +1,25 @@
+/**
+ * This rule is just a test.
+ *
+ * @module
+ */
+
+export const RULE_NAME = "test";
+
+export const rule: Deno.lint.Rule = {
+  create(ctx) {
+    const bannedVarName = "test";
+    const selector =
+      `VariableDeclaration > VariableDeclarator > Identifier[name="${bannedVarName}"]`;
+
+    return {
+      [selector](node: Deno.lint.Identifier) {
+        ctx.report({
+          message: `Do not use '${bannedVarName}' as a variable name.`,
+          node,
+          range: node.range,
+        });
+      },
+    };
+  },
+};

www/deno.json

@@ -3,5 +3,8 @@
     "start": "deno run -A --watch=static/,routes/,../src,../docs dev.ts",
     "build": "deno run -A dev.ts build",
     "preview": "deno serve -A _fresh/server.js"
+  },
+  "lint": {
+    "plugins": ["../lint/src/mod.ts"]
   }
 }