From 8dc1ee0adc2f14aa2f37c8514613c6835441b9f0 Mon Sep 17 00:00:00 2001
From: Tejas Kumar <tejas@contiamo.com>
Date: Thu, 19 Jul 2018 16:23:19 +0200
Subject: [PATCH] Add error handling to Poll, do not rerender polled results
 unless content changes

---
 package.json |  5 +++--
 src/Poll.tsx | 30 +++++++++++++++++++++++++-----
 yarn.lock    | 10 +++++++---
 3 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/package.json b/package.json
index 5f86b291..9ef9b1c7 100644
--- a/package.json
+++ b/package.json
@@ -67,10 +67,11 @@
     "tslint": "^5.10.0",
     "tslint-config-prettier": "^1.13.0",
     "tslint-plugin-blank-line": "^0.0.8",
-    "typescript": "^3.1.0-dev.20180717"
+    "typescript": "^2.9.2"
   },
   "dependencies": {
-    "react": "^16.4.1"
+    "react": "^16.4.1",
+    "react-fast-compare": "^2.0.1"
   },
   "peerDependencies": {
     "react": "^16.4.1"
diff --git a/src/Poll.tsx b/src/Poll.tsx
index 5407adf4..0180b046 100644
--- a/src/Poll.tsx
+++ b/src/Poll.tsx
@@ -1,4 +1,6 @@
 import React from "react";
+import equal from "react-fast-compare";
+
 import { RestfulReactConsumer } from "./Context";
 import { GetComponentProps, GetComponentState, Meta as GetComponentMeta } from "./Get";
 
@@ -147,6 +149,16 @@ class ContextlessPoll<T> extends React.Component<PollProps<T>, Readonly<PollStat
 
   private keepPolling = !this.props.lazy;
 
+  private isModified = (response: Response, nextData: T) => {
+    if (response.status === 304) {
+      return false;
+    }
+    if (equal(this.state.data, nextData)) {
+      return false;
+    }
+    return true;
+  };
+
   /**
    * This thing does the actual poll.
    */
@@ -173,11 +185,19 @@ class ContextlessPoll<T> extends React.Component<PollProps<T>, Readonly<PollStat
     const responseBody =
       response.headers.get("content-type") === "application/json" ? await response.json() : await response.text();
 
-    this.setState(() => ({
-      loading: false,
-      lastResponse: response,
-      data: resolve ? resolve(responseBody) : responseBody,
-    }));
+    if (!response.ok) {
+      const error = `${response.status} ${response.statusText}`;
+      this.setState({ loading: false, lastResponse: response, data: responseBody, error });
+      throw new Error(`Failed to Poll: ${error}`);
+    }
+
+    if (this.isModified(response, responseBody)) {
+      this.setState(() => ({
+        loading: false,
+        lastResponse: response,
+        data: resolve ? resolve(responseBody) : responseBody,
+      }));
+    }
 
     // Wait for interval to pass.
     await new Promise(resolvePromise => setTimeout(resolvePromise, interval));
diff --git a/yarn.lock b/yarn.lock
index de151228..052253e5 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3201,6 +3201,10 @@ rc@^1.2.7:
     minimist "^1.2.0"
     strip-json-comments "~2.0.1"
 
+react-fast-compare@^2.0.1:
+  version "2.0.1"
+  resolved "https://registry.yarnpkg.com/react-fast-compare/-/react-fast-compare-2.0.1.tgz#92c91ac4814aa8cfcfb04780ad1bfff2bbe3a3c6"
+
 react@^16.4.1:
   version "16.4.1"
   resolved "https://registry.yarnpkg.com/react/-/react-16.4.1.tgz#de51ba5764b5dbcd1f9079037b862bd26b82fe32"
@@ -3980,9 +3984,9 @@ type-check@~0.3.2:
   dependencies:
     prelude-ls "~1.1.2"
 
-typescript@^3.1.0-dev.20180717:
-  version "3.1.0-dev.20180717"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.1.0-dev.20180717.tgz#a623e4df35ee102641020b1fe9dd5258547be74a"
+typescript@^2.9.2:
+  version "2.9.2"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-2.9.2.tgz#1cbf61d05d6b96269244eb6a3bce4bd914e0f00c"
 
 ua-parser-js@^0.7.18:
   version "0.7.18"