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Replaced network.onRequestFinished() caching with network.getHAR()
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This avoids the need for us to redundantly (pre) cache JavaScript content. In the event that the HAR log doesn't contain a match, we'll fall back to fetching from the Network (and hoping for a cache hit from that layer).
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Brian Vaughn committed Sep 10, 2021
1 parent 0fd195f commit 649a424
Showing 1 changed file with 97 additions and 66 deletions.
163 changes: 97 additions & 66 deletions packages/react-devtools-extensions/src/main.js
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Original file line number Diff line number Diff line change
Expand Up @@ -19,33 +19,13 @@ import {
localStorageSetItem,
} from 'react-devtools-shared/src/storage';
import DevTools from 'react-devtools-shared/src/devtools/views/DevTools';
import {__DEBUG__} from 'react-devtools-shared/src/constants';

const LOCAL_STORAGE_SUPPORTS_PROFILING_KEY =
'React::DevTools::supportsProfiling';

const isChrome = getBrowserName() === 'Chrome';

const cachedNetworkEvents = new Map();

// Cache JavaScript resources as the page loads them.
// This helps avoid unnecessary duplicate requests when hook names are parsed.
// Responses with a Vary: 'Origin' might not match future requests.
// This lets us avoid a possible (expensive) cache miss.
// For more info see: github.com/facebook/react/pull/22198
chrome.devtools.network.onRequestFinished.addListener(
function onRequestFinished(event) {
if (event.request.method === 'GET') {
switch (event.response.content.mimeType) {
case 'application/javascript':
case 'application/x-javascript':
case 'text/javascript':
cachedNetworkEvents.set(event.request.url, event);
break;
}
}
},
);

let panelCreated = false;

// The renderer interface can't read saved component filters directly,
Expand Down Expand Up @@ -233,56 +213,113 @@ function createPanelIfReactLoaded() {
}
};

let debugIDCounter = 0;

// For some reason in Firefox, chrome.runtime.sendMessage() from a content script
// never reaches the chrome.runtime.onMessage event listener.
let fetchFileWithCaching = null;
if (isChrome) {
// Fetching files from the extension won't make use of the network cache
// for resources that have already been loaded by the page.
// This helper function allows the extension to request files to be fetched
// by the content script (running in the page) to increase the likelihood of a cache hit.
fetchFileWithCaching = url => {
const event = cachedNetworkEvents.get(url);
if (event != null) {
// If this resource has already been cached locally,
// skip the network queue (which might not be a cache hit anyway)
// and just use the cached response.
return new Promise(resolve => {
event.getContent(content => resolve(content));
});
const fetchFromNetworkCache = (url, resolve, reject) => {
// Debug ID allows us to avoid re-logging (potentially long) URL strings below,
// while also still associating (potentially) interleaved logs with the original request.
let debugID = null;

if (__DEBUG__) {
debugID = debugIDCounter++;
console.log(`[main] fetchFromNetworkCache(${debugID})`, url);
}

// If DevTools was opened after the page started loading,
// we may have missed some requests.
// So fall back to a fetch() and hope we get a cached response.

return new Promise((resolve, reject) => {
function onPortMessage({payload, source}) {
if (source === 'react-devtools-content-script') {
switch (payload?.type) {
case 'fetch-file-with-cache-complete':
chrome.runtime.onMessage.removeListener(onPortMessage);
resolve(payload.value);
break;
case 'fetch-file-with-cache-error':
chrome.runtime.onMessage.removeListener(onPortMessage);
reject(payload.value);
break;
chrome.devtools.network.getHAR(harLog => {
for (let i = 0; i < harLog.entries.length; i++) {
const entry = harLog.entries[i];
if (url === entry.request.url) {
if (__DEBUG__) {
console.log(
`[main] fetchFromNetworkCache(${debugID}) Found matching URL in HAR`,
url,
);
}

entry.getContent(content => {
if (content) {
if (__DEBUG__) {
console.log(
`[main] fetchFromNetworkCache(${debugID}) Content retrieved`,
);
}

resolve(content);
} else {
if (__DEBUG__) {
console.log(
`[main] fetchFromNetworkCache(${debugID}) Invalid content returned by getContent()`,
content,
);
}

// Edge case where getContent() returned null; fall back to fetch.
fetchFromPage(url, resolve);
}
});

return;
}
}

chrome.runtime.onMessage.addListener(onPortMessage);
if (__DEBUG__) {
console.log(
`[main] fetchFromNetworkCache(${debugID}) No cached request found in getHAR()`,
);
}

chrome.devtools.inspectedWindow.eval(`
window.postMessage({
source: 'react-devtools-extension',
payload: {
type: 'fetch-file-with-cache',
url: "${url}",
},
});
`);
// No matching URL found; fall back to fetch.
fetchFromPage(url, resolve);
});
};

const fetchFromPage = (url, resolve, reject) => {
if (__DEBUG__) {
console.log('[main] fetchFromPage()', url);
}

function onPortMessage({payload, source}) {
if (source === 'react-devtools-content-script') {
switch (payload?.type) {
case 'fetch-file-with-cache-complete':
chrome.runtime.onMessage.removeListener(onPortMessage);
resolve(payload.value);
break;
case 'fetch-file-with-cache-error':
chrome.runtime.onMessage.removeListener(onPortMessage);
reject(payload.value);
break;
}
}
}

chrome.runtime.onMessage.addListener(onPortMessage);

chrome.devtools.inspectedWindow.eval(`
window.postMessage({
source: 'react-devtools-extension',
payload: {
type: 'fetch-file-with-cache',
url: "${url}",
},
});
`);
};

// Fetching files from the extension won't make use of the network cache
// for resources that have already been loaded by the page.
// This helper function allows the extension to request files to be fetched
// by the content script (running in the page) to increase the likelihood of a cache hit.
fetchFileWithCaching = url => {
return new Promise((resolve, reject) => {
// Try fetching from the Network cache first.
// If DevTools was opened after the page started loading, we may have missed some requests.
// So fall back to a fetch() from the page and hope we get a cached response that way.
fetchFromNetworkCache(url, resolve, reject);
});
};
}
Expand Down Expand Up @@ -441,9 +478,6 @@ function createPanelIfReactLoaded() {

// Re-initialize DevTools panel when a new page is loaded.
chrome.devtools.network.onNavigated.addListener(function onNavigated() {
// Clear cached requests when a new page is opened.
cachedNetworkEvents.clear();

// Re-initialize saved filters on navigation,
// since global values stored on window get reset in this case.
syncSavedPreferences();
Expand All @@ -460,9 +494,6 @@ function createPanelIfReactLoaded() {

// Load (or reload) the DevTools extension when the user navigates to a new page.
function checkPageForReact() {
// Clear cached requests when a new page is opened.
cachedNetworkEvents.clear();

syncSavedPreferences();
createPanelIfReactLoaded();
}
Expand Down

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