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// A collection of helper functions that make use of the `remoteContextHelper`
// to test BFCache support and behavior.
// Call `prepareForBFCache()` before navigating away from the page. This simply
// sets a variable in window.
async function prepareForBFCache(remoteContextHelper) {
await remoteContextHelper.executeScript(() => {
window.beforeBFCache = true;
});
}
// Call `getBeforeCache()` after navigating back to the page. This returns the
// value in window.
async function getBeforeBFCache(remoteContextHelper) {
return await remoteContextHelper.executeScript(() => {
return window.beforeBFCache;
});
}
// If the value in window is set to true, this means that the page was reloaded,
// i.e., the page was restored from BFCache.
// Call `prepareForBFCache()` before navigating away to call this function.
async function assertImplementsBFCacheOptional(remoteContextHelper) {
var beforeBFCache = await getBeforeBFCache(remoteContextHelper);
assert_implements_optional(beforeBFCache == true, 'BFCache not supported.');
}
// Subtracts set `b` from set `a` and returns the result.
function setMinus(a, b) {
const minus = new Set();
a.forEach(e => {
if (!b.has(e)) {
minus.add(e);
}
});
return minus;
}
// Return a sorted Array from the iterable `s`.
function sorted(s) {
return Array.from(s).sort();
}
// Assert expected reasons are all present. Note that the extra reasons are allowed
// as UAs might block bfcache for their specific reasons.
function matchReasons(expectedNotRestoredReasonsSet, notRestoredReasonsSet) {
const missing = setMinus(
expectedNotRestoredReasonsSet, notRestoredReasonsSet, 'Missing reasons');
const extra = setMinus(
notRestoredReasonsSet, expectedNotRestoredReasonsSet, 'Extra reasons');
assert_true(missing.size == 0, `Expected: ${sorted(expectedNotRestoredReasonsSet)}\n` +
`Got: ${sorted(notRestoredReasonsSet)}\n` +
`Missing: ${sorted(missing)}\n` +
`Extra: ${sorted(extra)}\n`);
}
// This function takes a set of reasons and extracts reasons out of it and returns a set of strings.
// For example, if the input is [{"reason": "error-document"}, {"reason": "masked"}],
// the output is ["error-document", "masked"].
function extractReason(reasonSet) {
let reasonsExtracted = new Set();
for (let reason of reasonSet) {
reasonsExtracted.add(reason.reason);
}
return reasonsExtracted;
}
// A helper function to assert that the page is not restored from BFCache by
// checking whether the `beforeBFCache` value from `window` is undefined
// due to page reload.
// This function also takes an optional `notRestoredReasons` list which
// indicates the set of expected reasons that make the page not restored.
// If the reasons list is undefined, the check will be skipped. Otherwise
// this check will use the `notRestoredReasons` API, to obtain the reasons
// in a tree structure, and flatten the reasons before making the order-
// insensitive comparison.
// If the API is not available, the function will terminate instead of marking
// the assertion failed.
// Call `prepareForBFCache()` before navigating away to call this function.
async function assertNotRestoredFromBFCache(
remoteContextHelper, notRestoredReasons) {
var beforeBFCache = await getBeforeBFCache(remoteContextHelper);
assert_equals(beforeBFCache, undefined, 'document unexpectedly BFCached');
// The reason is optional, so skip the remaining test if the
// `notRestoredReasons` is not set.
if (notRestoredReasons === undefined) {
return;
}
let isFeatureEnabled = await remoteContextHelper.executeScript(() => {
return 'notRestoredReasons' in
performance.getEntriesByType('navigation')[0];
});
// Return if the `notRestoredReasons` API is not available.
if (!isFeatureEnabled) {
return;
}
let result = await remoteContextHelper.executeScript(() => {
return performance.getEntriesByType('navigation')[0].notRestoredReasons;
});
let expectedNotRestoredReasonsSet = new Set(notRestoredReasons);
let notRestoredReasonsSet = new Set();
// Flatten the reasons from the main frame and all the child frames.
const collectReason = (node) => {
for (let reason of node.reasons) {
notRestoredReasonsSet.add(reason.reason);
}
for (let child of node.children) {
collectReason(child);
}
};
collectReason(result);
matchReasons(expectedNotRestoredReasonsSet, notRestoredReasonsSet);
}
// A helper function that combines the steps of setting window property,
// navigating away and back, and making assertion on whether BFCache is
// supported.
// This function can be used to check if the current page is eligible for
// BFCache.
async function assertBFCacheEligibility(
remoteContextHelper, shouldRestoreFromBFCache) {
await prepareForBFCache(remoteContextHelper);
// Navigate away and back.
const newRemoteContextHelper = await remoteContextHelper.navigateToNew();
await newRemoteContextHelper.historyBack();
if (shouldRestoreFromBFCache) {
await assertImplementsBFCacheOptional(remoteContextHelper);
} else {
await assertNotRestoredFromBFCache(remoteContextHelper);
}
}