fix(esm): avoid errors, slightly deal with arrays

src/__tests__/formatPkg.test.js

@@ -1,4 +1,4 @@
-import formatPkg, { getRepositoryInfo } from '../formatPkg.js';
+import formatPkg, { getRepositoryInfo, getMains } from '../formatPkg.js';
 import rawPackages from './rawPackages.json';
 import preact from './preact-simplified.json';
 import isISO8601 from 'validator/lib/isISO8601.js';
@@ -502,4 +502,35 @@ describe('moduleTypes', () => {
   test('preact (esm & umd)', () => {
     expect(formatPkg(preact).moduleTypes).toEqual(['esm']);
   });
+
+  test('silly broken package', () => {
+    expect(
+      formatPkg({
+        name: 'whoever',
+        lastPublisher: { name: 'unknown' },
+        main: [{ personalMain: 'index.mjs' }],
+      }).moduleTypes
+    ).toEqual(['unknown']);
+  });
+});
+
+describe('getMain', () => {
+  test('main === string', () => {
+    expect(getMains({ main: 'index.js' })).toEqual(['index.js']);
+  });
+
+  test('first if array', () => {
+    expect(getMains({ main: ['index.js', 'ondex.jsx'] })).toEqual([
+      'index.js',
+      'ondex.jsx',
+    ]);
+  });
+
+  test('index.js if undefined', () => {
+    expect(getMains({ main: undefined })).toEqual(['index.js']);
+  });
+
+  test('nothing if object', () => {
+    expect(getMains({ main: { something: 'cool.js' } })).toEqual([]);
+  });
 });

src/formatPkg.js

@@ -406,7 +406,8 @@ function getTypes(pkg) {
     return { ts: 'included' };
   }
 
-  const main = pkg.main || 'index.js';
+  // we only look at the first entry in main here
+  const main = getMains(pkg)[0];
   if (typeof main === 'string' && main.endsWith('.js')) {
     const dtsMain = main.replace(/js$/, 'd.ts');
     return {
@@ -438,19 +439,37 @@ function getAlternativeNames(name) {
   );
 }
 
-function getModuleTypes(cleaned) {
-  const main = cleaned.main || '';
-  const moduleTypes = [];
-  if (
-    typeof cleaned.module === 'string' ||
-    cleaned.type === 'module' ||
-    main.endsWith('.mjs')
-  ) {
-    moduleTypes.push('esm');
+export function getMains(pkg) {
+  if (Array.isArray(pkg.main)) {
+    // we can not deal with non-string mains for now
+    return pkg.main.filter(main => typeof main === 'string');
+  }
+  if (typeof pkg.main === 'string') {
+    return [pkg.main];
   }
-  if (cleaned.type === 'commonjs' || main.endsWith('.cjs')) {
-    moduleTypes.push('cjs');
+  if (typeof pkg.main === 'undefined') {
+    return ['index.js'];
   }
+  // we can not deal with non-array ||non-string mains for now
+  return [];
+}
+
+function getModuleTypes(pkg) {
+  const mains = getMains(pkg);
+  const moduleTypes = [];
+
+  mains.forEach(main => {
+    if (
+      typeof pkg.module === 'string' ||
+      pkg.type === 'module' ||
+      main.endsWith('.mjs')
+    ) {
+      moduleTypes.push('esm');
+    }
+    if (pkg.type === 'commonjs' || main.endsWith('.cjs')) {
+      moduleTypes.push('cjs');
+    }
+  });
 
   if (moduleTypes.length === 0) {
     moduleTypes.push('unknown');