From f5e5c2877b19f2fcd6c6ed4fd7c344c9c9fcc2a1 Mon Sep 17 00:00:00 2001
From: Tim Hudson <tim.hudson15@gmail.com>
Date: Tue, 7 May 2019 18:35:10 -0400
Subject: [PATCH 1/4] Add test coverage that triggers Maximum call stack
 exception

---
 test/index.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/test/index.js b/test/index.js
index 4960c87ae..c1b157f5e 100644
--- a/test/index.js
+++ b/test/index.js
@@ -277,13 +277,15 @@ test('mapProps copies propTypes', t => {
 
 test('merge deeply merges', t => {
   const result = merge(
-    { hello: { hi: 'beep' } },
-    { hello: { hey: 'boop' } },
+    { hello: { hi: 'beep', merge: 'me', and: 'me' } },
+    { hello: { hey: 'boop', merge: 'me', and: 'all of us' } },
   )
   t.deepEqual(result, {
     hello: {
       hi: 'beep',
       hey: 'boop',
+      merge: 'me',
+      and: 'all of us'
     }
   })
 })

From 926f9f6c5fb697967c4772ce7eb8e11402270c85 Mon Sep 17 00:00:00 2001
From: Tim Hudson <tim.hudson15@gmail.com>
Date: Tue, 7 May 2019 19:06:20 -0400
Subject: [PATCH 2/4] Check that values are objects before merging

---
 src/index.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/index.js b/src/index.js
index 34bd955ca..216373323 100644
--- a/src/index.js
+++ b/src/index.js
@@ -44,8 +44,10 @@ export const merge = (a, b) => {
   for (const key in b) {
     if (!a[key]) {
       result[key] = b[key]
-    } else {
+    } else if (typeof a[key] === 'object') {
       result[key] = merge(a[key], b[key])
+    } else {
+      result[key] = b[key]
     }
   }
   return result

From bc70315e9624da7e37b6570ec3757714ac6ea5f4 Mon Sep 17 00:00:00 2001
From: Tim Hudson <tim.hudson15@gmail.com>
Date: Wed, 8 May 2019 06:27:47 -0400
Subject: [PATCH 3/4] Add realistic variant test case

---
 test/index.js | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/test/index.js b/test/index.js
index c1b157f5e..15aebefce 100644
--- a/test/index.js
+++ b/test/index.js
@@ -11,6 +11,7 @@ import {
   cloneFunction,
   mapProps,
   merge,
+  fontSize,
 } from '../src'
 
 const width = style({
@@ -289,3 +290,27 @@ test('merge deeply merges', t => {
     }
   })
 })
+
+test('variant can be composed', t => {
+  const system = compose(
+    variant({ key: 'typography' }),
+    fontSize,
+    color
+  )
+  const result = system({
+    theme: {
+      typography: {
+        primary: {
+          fontSize: '32px',
+          color: '#fff'
+        },
+      },
+    },
+    variant: 'primary',
+    color: '#111'
+  })
+  t.deepEqual(result, {
+    fontSize: '32px',
+    color: '#111'
+  })
+})

From cc67fbb7cd0f258d740a3a31cacc07c78733df62 Mon Sep 17 00:00:00 2001
From: Tim Hudson <tim.hudson15@gmail.com>
Date: Wed, 8 May 2019 10:46:34 -0400
Subject: [PATCH 4/4] Simplify merge conditional

---
 src/index.js | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/index.js b/src/index.js
index 216373323..6b28cfeff 100644
--- a/src/index.js
+++ b/src/index.js
@@ -42,12 +42,10 @@ export const merge = (a, b) => {
     result[key] = a[key]
   }
   for (const key in b) {
-    if (!a[key]) {
+    if (!a[key] || typeof a[key] !== 'object') {
       result[key] = b[key]
-    } else if (typeof a[key] === 'object') {
-      result[key] = merge(a[key], b[key])
     } else {
-      result[key] = b[key]
+      result[key] = merge(a[key], b[key])
     }
   }
   return result