From 0a1704bb9acc6e3a12a4e59cc118a29179a9117a Mon Sep 17 00:00:00 2001
From: Tim van der Horst <tim.vanderhorst@sportsmedglobal.com>
Date: Fri, 9 Jun 2017 12:30:55 +1000
Subject: [PATCH 1/2] feat: Extended diff option to allow for a custom differ
 function

---
 README.md         |  7 ++++---
 spec/diff.spec.js | 12 ++++++++++++
 src/core.js       |  3 ++-
 src/diff.js       |  4 ++--
 4 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/README.md b/README.md
index 2737cc0..842ea76 100644
--- a/README.md
+++ b/README.md
@@ -73,7 +73,7 @@ Note: logger **must be** the last middleware in chain, otherwise it will log thu
   logger = console: LoggerObject, // implementation of the `console` API.
   logErrors = true: Boolean, // should the logger catch, log, and re-throw errors?
 
-  diff = false: Boolean, // (alpha) show diff between states?
+  diff = false: Boolean | customDiffer, // (alpha) show diff between states?
   diffPredicate // (alpha) filter function for showing states diff, similar to `predicate`
 }
 ```
@@ -159,8 +159,9 @@ Format the title used for each action.
 
 *Default: prints something like `action @ ${time} ${action.type} (in ${took.toFixed(2)} ms)`*
 
-#### __diff (Boolean)__
-Show states diff.
+#### __diff = (prevState: Object, newState: Object) => diff__
+Show states diff. Takes a boolean or optionally a custom differ to use instead of the default
+[`deep-diff`](https://github.com/flitbit/diff).
 
 *Default: `false`*
 
diff --git a/spec/diff.spec.js b/spec/diff.spec.js
index a89b4bf..e71e42f 100644
--- a/spec/diff.spec.js
+++ b/spec/diff.spec.js
@@ -1,5 +1,6 @@
 import sinon from 'sinon';
 import { expect } from 'chai';
+import differ from 'deep-diff';
 import { style, render, default as diffLogger } from '../src/diff';
 
 context('Diff', () => {
@@ -111,5 +112,16 @@ context('Diff', () => {
 
       expect(logger.log.calledWithExactly('%c CHANGED:', 'color: #2196F3; font-weight: bold', 'name', 'kirk', '→', 'picard')).to.be.true;
     });
+
+    it('should use a custom differ if provided', () => {
+      const callback = sinon.spy();
+      const customDiffer = (prevState, newState) => {
+        callback();
+        return differ(prevState, newState);
+      };
+      diffLogger({name: 'kirk'}, {name: 'picard'}, logger, false, customDiffer);
+
+      expect(callback.called).to.be.true;
+    });
   });
 });
diff --git a/src/core.js b/src/core.js
index fba99bc..de7602c 100644
--- a/src/core.js
+++ b/src/core.js
@@ -46,6 +46,7 @@ function printBuffer(buffer, options) {
     level,
     diff,
   } = options;
+  const customDiffer = typeof diff === 'function' ? diff : undefined;
 
   const isUsingDefaultFormatter = typeof options.titleFormatter === 'undefined';
 
@@ -126,7 +127,7 @@ function printBuffer(buffer, options) {
     }
 
     if (diff) {
-      diffLogger(prevState, nextState, logger, isCollapsed);
+      diffLogger(prevState, nextState, logger, isCollapsed, customDiffer);
     }
 
     try {
diff --git a/src/diff.js b/src/diff.js
index 31d20d6..431f71d 100644
--- a/src/diff.js
+++ b/src/diff.js
@@ -41,8 +41,8 @@ export function render(diff) {
   }
 }
 
-export default function diffLogger(prevState, newState, logger, isCollapsed) {
-  const diff = differ(prevState, newState);
+export default function diffLogger(prevState, newState, logger, isCollapsed, customDiffer) {
+  const diff = (customDiffer || differ)(prevState, newState);
 
   try {
     if (isCollapsed) {

From b1f3281a3392ea9381baf39b6cb2a83abfd161b3 Mon Sep 17 00:00:00 2001
From: Tim van der Horst <tim.vanderhorst@sportsmedglobal.com>
Date: Mon, 12 Jun 2017 14:07:20 +1000
Subject: [PATCH 2/2] Changed custom differ to be a parameter defaulting to
 `deep-diff`

---
 spec/diff.spec.js | 4 ++--
 src/diff.js       | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/spec/diff.spec.js b/spec/diff.spec.js
index e71e42f..599e7cd 100644
--- a/spec/diff.spec.js
+++ b/spec/diff.spec.js
@@ -1,6 +1,6 @@
 import sinon from 'sinon';
 import { expect } from 'chai';
-import differ from 'deep-diff';
+import deepDiff from 'deep-diff';
 import { style, render, default as diffLogger } from '../src/diff';
 
 context('Diff', () => {
@@ -117,7 +117,7 @@ context('Diff', () => {
       const callback = sinon.spy();
       const customDiffer = (prevState, newState) => {
         callback();
-        return differ(prevState, newState);
+        return deepDiff(prevState, newState);
       };
       diffLogger({name: 'kirk'}, {name: 'picard'}, logger, false, customDiffer);
 
diff --git a/src/diff.js b/src/diff.js
index 431f71d..b51ded2 100644
--- a/src/diff.js
+++ b/src/diff.js
@@ -1,4 +1,4 @@
-import differ from 'deep-diff';
+import deepDiff from 'deep-diff';
 
 // https://github.com/flitbit/diff#differences
 const dictionary = {
@@ -41,8 +41,8 @@ export function render(diff) {
   }
 }
 
-export default function diffLogger(prevState, newState, logger, isCollapsed, customDiffer) {
-  const diff = (customDiffer || differ)(prevState, newState);
+export default function diffLogger(prevState, newState, logger, isCollapsed, differ = deepDiff) {
+  const diff = differ(prevState, newState);
 
   try {
     if (isCollapsed) {