Add handling of parent being absent from cache and parent being self

fixture-importer.js

@@ -0,0 +1,7 @@
+const importFresh = require('.');
+
+module.exports = what => {
+	return importFresh(what);
+};
+
+module.exports.__filename = __filename;

index.js

@@ -24,9 +24,9 @@ module.exports = moduleId => {
 		}
 	}
 
-	// Delete module from cache
-	delete require.cache[filePath];
+	delete require.cache[filePath]; // Delete module from cache
 
-	// Return fresh module
-	return require.cache[parentPath].require(filePath);
+	const parent = require.cache[parentPath]; // If `filePath` and `parentPath` are the same, cache will already be deleted so we won't get a memory leak in next step
+
+	return parent === undefined ? require(filePath) : parent.require(filePath); // In case cache doesn't have parent, fall back to normal require
 };

test.js

@@ -21,3 +21,20 @@ test('proper parent value', t => {
 	const childModule = require.cache[path.resolve(__dirname, `${id}.js`)];
 	t.is(childModule.parent, module);
 });
+
+test('self import', t => {
+	const id = './fixture-importer';
+	t.notThrows(() => {
+		importFresh(id)(id);
+	});
+});
+
+test('import when parent removed from cache', t => {
+	const id = './fixture-importer';
+	const importer = importFresh(id);
+	t.true(require.cache[importer.__filename] !== undefined);
+	delete require.cache[importer.__filename];
+	t.notThrows(() => {
+		importer(id);
+	});
+});