From c4336dd0cc185b692ebba896f0da9eb9067af27d Mon Sep 17 00:00:00 2001
From: Javi Velasco <javier.velasco86@gmail.com>
Date: Sat, 28 Jan 2017 12:08:02 +0100
Subject: [PATCH] Warn the case when a string is being merged with an object

---
 src/components/themr.js       | 6 ++++++
 test/components/themr.spec.js | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/src/components/themr.js b/src/components/themr.js
index 01c6745..97a2328 100644
--- a/src/components/themr.js
+++ b/src/components/themr.js
@@ -183,6 +183,12 @@ export function themeable(original = {}, mixin) {
 
       let newValue
 
+      //when you are mixing an string with a object it should fail
+      invariant(!(typeof originalValue === 'string' && typeof mixinValue === 'object'),
+        `You are merging a string "${originalValue}" with an Object,` +
+        'Make sure you are passing the proper theme descriptors.'
+      )
+
       //check if values are nested objects
       if (typeof originalValue === 'object' && typeof mixinValue === 'object') {
         //go recursive
diff --git a/test/components/themr.spec.js b/test/components/themr.spec.js
index 749158b..51b564b 100644
--- a/test/components/themr.spec.js
+++ b/test/components/themr.spec.js
@@ -555,4 +555,10 @@ describe('themeable function', () => {
     const result = themeable(themeA, themeB)
     expect(result).toEqual(expected)
   })
+
+  it('throws an exception when its called mixing a string with an object', () => {
+    expect(() => {
+      themeable('fail', { test: { foo: 'baz' } })
+    }).toThrow(/sure you are passing the proper theme descriptors/)
+  })
 })