fix: check undefined string and show how to correct

Author: seongwon-kang

src/createTag/createTag.js

@@ -93,6 +93,12 @@ export default function createTag(...rawTransformers) {
     if (!Array.isArray(strings)) {
       return tag([strings]);
     }
+    
+    if (typeof strings[0] === 'undefined') {
+      throw TypeError(`input string is undefined: Check your template string. 
+        (e.g. \\4 will throw SyntaxError with 'Octal escape sequences are not allowed')
+      `);
+    }
 
     const tagCallInfo = getTagCallInfo(transformers);
 

src/createTag/createTag.test.js

@@ -298,3 +298,16 @@ test('accepts other tags as arguments and applies them in order', () => {
 
   expect(superTag`foo`).toBe('foo1234');
 });
+
+test('invalid template string should throw error message', () => {
+  const getInitialContext = jest.fn();
+  const tag = createTag({ getInitialContext });
+
+  let actual = ()=> {
+    tag`\4`;
+  };
+
+  expect(actual).toThrow(
+    `input string is undefined: Check your template string.`,
+  );
+});