detect test files if tsx --test script is present

packages/knip/fixtures/plugins/tsx/package.json

@@ -0,0 +1,9 @@
+{
+  "name": "@fixtures/tsx",
+  "devDependencies": {
+    "tsx": "*"
+  },
+  "scripts": {
+    "test": "tsx --test"
+  }
+}

packages/knip/src/plugins/tsx/index.ts

@@ -1,9 +1,38 @@
-import type { Plugin } from '../../types/config.js';
+import type { PackageJson } from 'src/types/package-json.js';
+import { toDependency, toEntry } from 'src/util/input.js';
+import { hasDependency } from 'src/util/plugin.js';
+import type { IsPluginEnabled, Plugin, ResolveConfig } from '../../types/config.js';
 
 // https://tsx.is
 
 const title = 'tsx';
 
+const enablers = ['tsx'];
+
+const isEnabled: IsPluginEnabled = ({ dependencies }) => hasDependency(dependencies, enablers);
+
+const config = ['package.json'];
+
+const packageJsonPath = (id: PackageJson) => id;
+
+const resolveConfig: ResolveConfig<PackageJson> = localConfig => {
+  const scripts = localConfig.scripts;
+
+  const entries = [toDependency('tsx')];
+
+  if (scripts && Object.keys(scripts).some(script => /(?<=^|\s)tsx\s(.*)--test/.test(scripts[script]))) {
+    const patterns = [
+      '**/*{.,-,_}test.?(c|m)(j|t)s',
+      '**/test-*.?(c|m)(j|t)s',
+      '**/test.?(c|m)(j|t)s',
+      '**/test/**/*.?(c|m)(j|t)s',
+    ];
+    entries.push(...patterns.map(id => toEntry(id)));
+  }
+
+  return entries;
+};
+
 const args = {
   positional: true,
   nodeImportArgs: true,
@@ -12,5 +41,9 @@ const args = {
 
 export default {
   title,
+  isEnabled,
+  packageJsonPath,
+  config,
+  resolveConfig,
   args,
 } satisfies Plugin;

packages/knip/test/plugins/tsx.test.ts

@@ -0,0 +1,21 @@
+import { test } from 'bun:test';
+import assert from 'node:assert/strict';
+import { main } from '../../src/index.js';
+import { resolve } from '../../src/util/path.js';
+import baseArguments from '../helpers/baseArguments.js';
+import baseCounters from '../helpers/baseCounters.js';
+
+const cwd = resolve('fixtures/plugins/tsx');
+
+test('Find dependencies with the tsx plugin', async () => {
+  const { counters } = await main({
+    ...baseArguments,
+    cwd,
+  });
+
+  assert.deepEqual(counters, {
+    ...baseCounters,
+    processed: 2,
+    total: 2,
+  });
+});