feat: load entrypoints from package.json

lib/cli.ts

@@ -28,6 +28,13 @@ const options = [
     description: 'Recursively look into files until the project is clean',
     default: false,
   },
+  {
+    name: 'read-package-json',
+    alias: 'P',
+    type: 'boolean',
+    description: 'Load entrypoints defined in package.json',
+    default: false,
+  },
   {
     name: 'include-d-ts',
     type: 'boolean',
@@ -76,6 +83,9 @@ Examples:
   # Check unused code for a project with a custom tsconfig.json
   tsr --project tsconfig.app.json 'src/main\\.ts$'
 
+  # Load entrypoints from package.json
+  tsr --read-package-json
+
   # Check unused code for a project with multiple entrypoints in src/pages
   tsr 'src/pages/.*\\.ts$'
 
@@ -105,6 +115,7 @@ const main = () => {
     configFile: parsed.project || 'tsconfig.json',
     recursive: parsed.recursive,
     includeDts: parsed['include-d-ts'],
+    readPackageJson: parsed['read-package-json'],
   }).catch((error) => {
     if (error instanceof CheckResultError || error instanceof ArgError) {
       process.exitCode = 1;

lib/tsr.ts

@@ -8,6 +8,7 @@ import { relative, resolve } from 'node:path';
 import { formatCount } from './util/formatCount.js';
 import { CliOutput } from './util/CliOutput.js';
 import { ArgError, CheckResultError } from './util/error.js';
+import { loadEntrypoints } from './util/loadEntrypoints.js';
 
 const createNodeJsLogger = (): Logger =>
   'isTTY' in stdout && stdout.isTTY
@@ -34,6 +35,7 @@ export type Config = {
   system?: ts.System;
   logger?: Logger;
   includeDts?: boolean;
+  readPackageJson?: boolean;
 };
 
 // is async for backwards compatibility
@@ -46,6 +48,7 @@ export const tsr = async ({
   system = ts.sys,
   logger = createNodeJsLogger(),
   includeDts = false,
+  readPackageJson = false,
 }: Config) => {
   const configPath = resolve(projectRoot, configFile);
 
@@ -63,6 +66,12 @@ export const tsr = async ({
     fileNames.map((n) => [n, system.readFile(n) || '']),
   );
 
+  if (readPackageJson) {
+    fileService.set('/package.json', system.readFile('package.json') || '');
+    entrypoints = entrypoints.concat(loadEntrypoints({ options, fileService }));
+    fileService.delete('/package.json');
+  }
+
   const entrypointFiles = fileNames.filter(
     (fileName) =>
       entrypoints.some((regex) => regex.test(fileName)) ||

lib/util/loadEntrypoints.test.ts

@@ -0,0 +1,32 @@
+import { describe, it } from 'node:test';
+import { MemoryFileService } from './MemoryFileService.js';
+import assert from 'node:assert/strict';
+import ts from 'typescript';
+import { loadEntrypoints } from './loadEntrypoints.js';
+
+describe('loadEntrypoints', () => {
+  it('should load entrypoints from package.json using tsconfig as reference', async () => {
+    const options: ts.CompilerOptions = {
+      rootDir: '/src',
+      outDir: '/dist',
+    };
+    const fileService = new MemoryFileService();
+    fileService.set(
+      '/package.json',
+      JSON.stringify({
+        bin: './dist/cli.js',
+        main: './dist/index.js',
+        exports: { '.': 'dist/default-export.js' },
+      }),
+    );
+    fileService.set(
+      '/src/index.ts',
+      `export const a = 'a'; export const a2 = 'a2';`,
+    );
+    assert.deepEqual(loadEntrypoints({ options, fileService }), [
+      new RegExp(/^\/src\/cli\.(js|jsx|ts|tsx|mjs|mts)$/),
+      new RegExp(/^\/src\/index\.(js|jsx|ts|tsx|mjs|mts)$/),
+      new RegExp(/^\/src\/default\x2dexport\.(js|jsx|ts|tsx|mjs|mts)$/),
+    ]);
+  });
+});

lib/util/loadEntrypoints.ts

@@ -0,0 +1,68 @@
+import path from 'node:path';
+import type ts from 'typescript';
+import { FileService } from './FileService.js';
+import escapeStringRegexp from 'escape-string-regexp';
+
+// circular references https://github.com/microsoft/TypeScript/issues/3496#issuecomment-128553540
+type PackageJsonExports = string | PackageJsonExportsObject;
+interface PackageJsonExportsObject {
+  [x: string]: PackageJsonExports;
+}
+
+interface PackageJson {
+  // https://nodejs.org/api/packages.html#package-entry-points
+  // https://nodejs.org/api/packages.html#conditional-exports
+  bin?: string;
+  main?: string;
+  exports?: PackageJsonExports;
+}
+
+function findPackageJsonExportsEntries(
+  exports: PackageJsonExports,
+  results: string[],
+): void {
+  if (typeof exports === 'string') results.push(exports);
+  if (exports !== null && typeof exports === 'object')
+    for (const value of Object.values(exports))
+      findPackageJsonExportsEntries(value, results);
+}
+
+export const loadEntrypoints = ({
+  options,
+  fileService,
+}: {
+  options: ts.CompilerOptions;
+  fileService: FileService;
+}): RegExp[] => {
+  if (!options.outDir || !options.rootDir) return [];
+
+  const packageJson = JSON.parse(
+    fileService.get('/package.json'),
+  ) as PackageJson;
+
+  const entries = [];
+
+  if (packageJson.bin) entries.push(packageJson.bin);
+  if (packageJson.main) entries.push(packageJson.main);
+  if (packageJson.exports)
+    findPackageJsonExportsEntries(packageJson.exports, entries);
+
+  const outDir = path.basename(options.outDir);
+
+  return entries.map((entry) => {
+    const ext = path.extname(entry);
+
+    const relativePath = path.relative(outDir, entry);
+    const rootDirRelative = path.join(options.rootDir!, relativePath);
+
+    // remove extension
+    const dirname = path.dirname(rootDirRelative);
+    const base = path.basename(rootDirRelative, ext);
+
+    const fullPathNoExt = path.join(dirname, base);
+
+    return new RegExp(
+      `^${escapeStringRegexp(fullPathNoExt)}\\.(js|jsx|ts|tsx|mjs|mts)$`,
+    );
+  });
+};

package.json

@@ -36,6 +36,7 @@
     "typescript-eslint": "^8.14.0"
   },
   "dependencies": {
+    "escape-string-regexp": "^5.0.0",
     "mri": "^1.2.0",
     "picocolors": "^1.1.1"
   },