fromAST: add explicit null guard

index.js

@@ -41,10 +41,12 @@ module.exports = function(file, callback) {
 /**
  * Determine the module type from an AST node
  *
- * @param  {Object} node
- * @return {String | null}
+ * @param  {Object|null|undefined} node
+ * @return {String|null}
  */
 function fromAST(node) {
+  if (!node) return null;
+
   if (types.isNamedForm(node)) return 'named';
   if (types.isDependencyForm(node)) return 'deps';
   if (types.isREMForm(node)) return 'rem';

test/test.js

@@ -92,3 +92,15 @@ fromSourceTests('should throw an error if an argument is missing', () => {
 });
 
 fromSourceTests.run();
+
+const fromASTTests = suite('From AST tests');
+
+fromASTTests('returns null for a null node', () => {
+  assert.equal(getType.fromAST(null), null);
+});
+
+fromASTTests('returns null for an undefined node', () => {
+  assert.equal(getType.fromAST(undefined), null);
+});
+
+fromASTTests.run();