From ae338441f0f49db67a2c7401d11b243540913ba3 Mon Sep 17 00:00:00 2001
From: Domenico de Feo <domenico.defeo@gmail.com>
Date: Thu, 22 Aug 2019 10:41:40 +0200
Subject: [PATCH] fix track and untracked changes and logs (#1)

---
 src/index.js      | 49 ++++++++++++++++++++++++-----------------------
 src/index.spec.js | 26 +++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 24 deletions(-)

diff --git a/src/index.js b/src/index.js
index f06aca3..f21fd4a 100644
--- a/src/index.js
+++ b/src/index.js
@@ -26,47 +26,48 @@ const WARN_COUNT = 1;
 const RESET_COUNT_INTERVAL = 1000;
 const SHOW_UNKNOWN_PROP_WARNING = true;
 
+// Find the keys that have changed since last render
 function findChanges(prev, next) {
-  // Find the keys that have changed since last render
-  const changed = Object.entries(next)
+  return Object.entries(next)
     .map(([key, val]) => (prev[key] !== val ? key : false))
     .filter(Boolean);
+}
 
-  // Are there any? Should we use singular or plural?
-  const count = changed.length;
-
-  if (!count) {
-    // There was a re-render but we're not tracking it
-    if (SHOW_UNKNOWN_PROP_WARNING === true) {
-      console.warn(
-        `An unknown data item has triggered a re-render. Chances are you're not providing it to %creact-whyupdate`,
-        'font-face: monospace; font-size: 0.65rem; font-style: italic;'
-      );
-    }
-    return;
+// Log or Warn about the changes
+function logChanges(changes) {
+  const count = changes.length;
+  if (!count && SHOW_UNKNOWN_PROP_WARNING) {
+    console.warn(
+      `An unknown data item has triggered a re-render. Chances are you're not providing it to %creact-whyupdate`,
+      'font-face: monospace; font-size: 0.65rem; font-style: italic;'
+    );
+  }
+  else if (count) {
+    console.log(
+      `Key${count > 1 ? 's' : ''} %c ${changes.join(', ')} %c ${count > 1 ? 'have' : 'has'} changed`,
+      'background: #FF5C5D; color: #F5F5F5; padding: 3px;',
+      'color: "inherit", background: "inherit"'
+    );
   }
-
-  // List all properties that have changed in this run
-  console.log(
-    `Key${count > 1 ? 's' : ''} %c ${changed.join(', ')} %c ${count > 1 ? 'have' : 'has'} changed`,
-    'background: #FF5C5D; color: #F5F5F5; padding: 3px;',
-    'color: "inherit", background: "inherit"'
-  );
 }
 
 function useWhyUpdate(...args) {
   if (process.env.NODE_ENV !== 'production') {
     // Initialize ref for the initial render
-    const ref = useRef({ time: Date.now(), count: 1, args, warn: undefined });
+    const ref = useRef({ time: Date.now(), count: 0, args, warn: undefined });
 
     // Previous props will be in ref.current.args
     const prev = ref.current.args;
 
     // compare previous and next only if previous exist
-    if (prev && Array.isArray(args)) {
+    if (prev && Array.isArray(args) && ref.current.count) {
+      
       // compare previous argument to the next one. Make sure indices are matched
       if (ref.current.count >= WARN_COUNT) {
-        args.forEach((next, idx) => findChanges(prev[idx], next));
+        const changes = args
+          .map((next, idx) => findChanges(prev[idx], next))
+          .reduce((acc, arg) => acc.concat(arg));
+        logChanges(changes);
       }
 
       // if it's been a while since the last re-render then it's a good time to reset update count
diff --git a/src/index.spec.js b/src/index.spec.js
index 7de57c7..13a62fc 100644
--- a/src/index.spec.js
+++ b/src/index.spec.js
@@ -3,6 +3,7 @@ import { create } from 'react-test-renderer';
 import useWhyUpdate from './index';
 
 const log = jest.spyOn(console, 'log').mockImplementation();
+const warn = jest.spyOn(console, 'warn').mockImplementation();
 
 const HINT_REGXP = /opportunity for improvement/;
 
@@ -18,6 +19,18 @@ const ThreeUpdates = (props = {}) => {
   return <div>{count}</div>;
 };
 
+const OneUntrackedUpdate = (props = {}) => {
+  const [untrackedCount, setUntrackedCount] = useState(0);
+  useEffect(() => {
+    if (untrackedCount < 1) {
+      setUntrackedCount(untrackedCount + 1);
+    }
+  }, [untrackedCount]);
+  useWhyUpdate(props);
+
+  return <div>{untrackedCount}</div>;
+};
+
 const NoState = props => {
   useWhyUpdate(props);
   return <div>Nothing happening here</div>;
@@ -50,6 +63,19 @@ describe('useWhyChange', () => {
     log.mockClear();
   });
 
+  it(`renders with one untracked state update`, async () => {
+    create(<OneUntrackedUpdate />);
+    // give it a cycle to process updates
+    await pause(100);
+    // log called zero times
+    expect(log).toHaveBeenCalledTimes(0);
+    // warn called once for each untracked update (1) 
+    expect(warn).toHaveBeenCalledTimes(1);
+    // clear any stale timeouts
+    Array.from(new Array(10), (_, idx) => clearTimeout(idx));
+    log.mockClear();
+  });
+
   it(`shows _too many updates_ hint`, async () => {
     create(<ThreeUpdates />);
     await pause(1200);