fix: mark vercel.ts config as used

README.md

@@ -84,7 +84,7 @@ For cleanup-specific findings:
 npx fallow dead-code
 ```
 
-116 framework plugins. No Node.js runtime required for static analysis. No config needed for the first run.
+117 framework plugins. No Node.js runtime required for static analysis. No config needed for the first run.
 
 ## What is Fallow?
 
@@ -749,14 +749,15 @@ See the [full configuration reference](https://docs.fallow.tools/configuration/o
 
 ## Framework plugins
 
-116 built-in plugins detect entry points, convention exports, config-defined aliases, and template-visible usage for your framework automatically.
+117 built-in plugins detect entry points, convention exports, config-defined aliases, and template-visible usage for your framework automatically.
 
 | Category | Plugins |
 |---|---|
 | **Frameworks** | Next.js, Nuxt, Remix, Qwik, SvelteKit, Gatsby, Astro, Angular, NestJS, AdonisJS, Contentlayer, Fumadocs, Lit, Obsidian, Ember, Expo, Expo Router, Electron, and more |
 | **Bundlers** | Vite, Webpack, Rspack, Rsbuild, Rollup, Rolldown, Tsup, Tsdown, pkg-utils, Parcel |
 | **Testing** | Vitest, Jest, Playwright, Cypress, Storybook, Stryker, Mocha, Ava, tap, tsd |
 | **CI/CD & Release** | Danger, Commitlint, Commitizen, Semantic Release |
+| **Deployment** | Vercel, Wrangler, Sentry, OpenNext Cloudflare |
 | **CSS** | Tailwind, PostCSS, UnoCSS, PandaCSS |
 | **Databases & Backend** | Prisma, Drizzle, Knex, TypeORM, Kysely, Convex |
 | **Blockchain** | Hardhat |

crates/core/src/plugins/mod.rs

@@ -1228,6 +1228,7 @@ mod typescript;
 mod unocss;
 mod varlock;
 mod velite;
+mod vercel;
 mod vite;
 mod vitepress;
 mod vitest;

crates/core/src/plugins/registry/builtin.rs

@@ -34,9 +34,10 @@ use super::super::{
     tailwind::TailwindPlugin, tanstack_router::TanstackRouterPlugin, tap::TapPlugin,
     tsd::TsdPlugin, tsdown::TsdownPlugin, tsup::TsupPlugin, turborepo::TurborepoPlugin,
     typedoc::TypedocPlugin, typeorm::TypeormPlugin, typescript::TypeScriptPlugin,
-    unocss::UnoCssPlugin, varlock::VarlockPlugin, velite::VelitePlugin, vite::VitePlugin,
-    vitepress::VitePressPlugin, vitest::VitestPlugin, webdriverio::WebdriverioPlugin,
-    webpack::WebpackPlugin, wrangler::WranglerPlugin, wuchale::WuchalePlugin, wxt::WxtPlugin,
+    unocss::UnoCssPlugin, varlock::VarlockPlugin, velite::VelitePlugin, vercel::VercelPlugin,
+    vite::VitePlugin, vitepress::VitePressPlugin, vitest::VitestPlugin,
+    webdriverio::WebdriverioPlugin, webpack::WebpackPlugin, wrangler::WranglerPlugin,
+    wuchale::WuchalePlugin, wxt::WxtPlugin,
 };
 
 /// Create all built-in plugin instances, categorized by domain.
@@ -145,6 +146,7 @@ pub fn create_builtin_plugins() -> Vec<Box<dyn Plugin>> {
         // Blockchain
         Box::new(HardhatPlugin),
         // Deployment
+        Box::new(VercelPlugin),
         Box::new(WranglerPlugin),
         Box::new(OpenNextCloudflarePlugin),
         Box::new(SentryPlugin),

crates/core/src/plugins/vercel.rs

@@ -0,0 +1,20 @@
+//! Vercel plugin.
+
+use super::{Plugin, PluginResult};
+
+const ENABLERS: &[&str] = &["vercel", "@vercel/config"];
+
+const CONFIG_PATTERNS: &[&str] = &["vercel.{ts,js,mjs,cjs,mts}"];
+
+const ALWAYS_USED: &[&str] = &["vercel.{ts,js,mjs,cjs,mts}"];
+
+const TOOLING_DEPENDENCIES: &[&str] = &["vercel", "@vercel/config"];
+
+define_plugin! {
+    struct VercelPlugin => "vercel",
+    enablers: ENABLERS,
+    config_patterns: CONFIG_PATTERNS,
+    always_used: ALWAYS_USED,
+    tooling_dependencies: TOOLING_DEPENDENCIES,
+    resolve_config: imports_only,
+}

crates/core/tests/integration_test.rs

@@ -191,6 +191,8 @@ mod issue_635_scaffold_template_assets;
 mod issue_638_node_script_entrypoints;
 #[path = "integration_test/issue_754_eslint_meta_preset.rs"]
 mod issue_754_eslint_meta_preset;
+#[path = "integration_test/issue_820_vercel_ts_config.rs"]
+mod issue_820_vercel_ts_config;
 #[path = "integration_test/lexical_nodes.rs"]
 mod lexical_nodes;
 #[path = "integration_test/script_multiplexers.rs"]

crates/core/tests/integration_test/issue_820_vercel_ts_config.rs

@@ -0,0 +1,39 @@
+//! Issue #820: Vercel programmatic config files are convention entrypoints.
+
+use super::common::{create_config, fixture_path};
+
+fn unused_file_paths(
+    root: &std::path::Path,
+    results: &fallow_types::results::AnalysisResults,
+) -> Vec<String> {
+    results
+        .unused_files
+        .iter()
+        .map(|finding| {
+            finding
+                .file
+                .path
+                .strip_prefix(root)
+                .unwrap_or(&finding.file.path)
+                .to_string_lossy()
+                .replace('\\', "/")
+        })
+        .collect()
+}
+
+#[test]
+fn vercel_ts_config_is_not_reported_as_unused() {
+    let root = fixture_path("issue-820-vercel-ts-config");
+    let config = create_config(root.clone());
+    let results = fallow_core::analyze(&config).expect("analysis should succeed");
+
+    let unused_paths = unused_file_paths(&root, &results);
+    assert!(
+        !unused_paths.contains(&"vercel.ts".to_string()),
+        "vercel.ts is loaded by Vercel convention and must be credited, got {unused_paths:?}"
+    );
+    assert!(
+        unused_paths.contains(&"src/orphan.ts".to_string()),
+        "ordinary unused file should still be reported, got {unused_paths:?}"
+    );
+}

tests/fixtures/issue-820-vercel-ts-config/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "issue-820-vercel-ts-config",
+  "version": "1.0.0",
+  "type": "module",
+  "main": "src/index.ts",
+  "devDependencies": {
+    "@vercel/config": "latest",
+    "vercel": "latest"
+  }
+}

tests/fixtures/issue-820-vercel-ts-config/src/index.ts

@@ -0,0 +1,3 @@
+export const greeting = "hello";
+
+console.log(greeting);

tests/fixtures/issue-820-vercel-ts-config/src/orphan.ts

@@ -0,0 +1 @@
+export const orphan = "unused";

tests/fixtures/issue-820-vercel-ts-config/vercel.ts

@@ -0,0 +1,6 @@
+import type { VercelConfig } from "@vercel/config/v1";
+
+export const config = {
+  regions: ["dub1"],
+  fluid: true,
+} satisfies VercelConfig;