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Fix bug where calling load() on lazy element breaks the loading #66

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Merged
merged 2 commits into from
Jul 29, 2021
Merged

Fix bug where calling load() on lazy element breaks the loading #66

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e1b4bd0
Add failing test for preload bug
Jul 29, 2021
2d22690
Move load() to be a private function and call caching getData from lo…
Jul 29, 2021
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83 changes: 43 additions & 40 deletions src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@ const privateData = new WeakMap()
const observer = new IntersectionObserver(entries => {
for(const entry of entries) {
if (entry.isIntersecting) {
const {target} = entry
const {target} = entry
observer.unobserve(target)
if (!(target instanceof IncludeFragmentElement)) return
if (target.loading === 'lazy') {
Expand Down Expand Up @@ -52,7 +52,7 @@ function getData(el: IncludeFragmentElement) {
return data.data
} else {
if (src) {
data = el.load()
data = fetchDataWithEvents(el)
} else {
data = Promise.reject(new Error('missing src'))
}
Expand All @@ -61,6 +61,46 @@ function getData(el: IncludeFragmentElement) {
}
}

function fetchDataWithEvents(el: IncludeFragmentElement) {
// We mimic the same event order as <img>, including the spec
// which states events must be dispatched after "queue a task".
// https://www.w3.org/TR/html52/semantics-embedded-content.html#the-img-element
return task()
.then(() => {
el.dispatchEvent(new Event('loadstart'))
return el.fetch(el.request())
})
.then(response => {
if (response.status !== 200) {
throw new Error(`Failed to load resource: the server responded with a status of ${response.status}`)
}
const ct = response.headers.get('Content-Type')
if (!isWildcard(el.accept) && (!ct || !ct.includes(el.accept ? el.accept : 'text/html'))) {
throw new Error(`Failed to load resource: expected ${el.accept || 'text/html'} but was ${ct}`)
}
return response.text()
})
.then(data => {
// Dispatch `load` and `loadend` async to allow
// the `load()` promise to resolve _before_ these
// events are fired.
task().then(() => {
el.dispatchEvent(new Event('load'))
el.dispatchEvent(new Event('loadend'))
})
return data
}, error => {
// Dispatch `error` and `loadend` async to allow
// the `load()` promise to resolve _before_ these
// events are fired.
task().then(() => {
el.dispatchEvent(new Event('error'))
el.dispatchEvent(new Event('loadend'))
})
throw error
})
}

function isWildcard(accept: string | null) {
return accept && !!accept.split(',').find(x => x.match(/^\s*\*\/\*/))
}
Expand Down Expand Up @@ -146,44 +186,7 @@ export default class IncludeFragmentElement extends HTMLElement {
}

load(): Promise<string> {
observer.unobserve(this)
// We mimic the same event order as <img>, including the spec
// which states events must be dispatched after "queue a task".
// https://www.w3.org/TR/html52/semantics-embedded-content.html#the-img-element
return task()
.then(() => {
this.dispatchEvent(new Event('loadstart'))
return this.fetch(this.request())
})
.then(response => {
if (response.status !== 200) {
throw new Error(`Failed to load resource: the server responded with a status of ${response.status}`)
}
const ct = response.headers.get('Content-Type')
if (!isWildcard(this.accept) && (!ct || !ct.includes(this.accept ? this.accept : 'text/html'))) {
throw new Error(`Failed to load resource: expected ${this.accept || 'text/html'} but was ${ct}`)
}
return response.text()
})
.then(data => {
// Dispatch `load` and `loadend` async to allow
// the `load()` promise to resolve _before_ these
// events are fired.
task().then(() => {
this.dispatchEvent(new Event('load'))
this.dispatchEvent(new Event('loadend'))
})
return data
}, error => {
// Dispatch `error` and `loadend` async to allow
// the `load()` promise to resolve _before_ these
// events are fired.
task().then(() => {
this.dispatchEvent(new Event('error'))
this.dispatchEvent(new Event('loadend'))
})
throw error
})
return getData(this)
}

fetch(request: RequestInfo): Promise<Response> {
Expand Down
5 changes: 3 additions & 2 deletions test/test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -485,7 +485,6 @@ suite('include-fragment-element', function() {
const div = document.createElement('div')
div.innerHTML = '<include-fragment loading="lazy" src="/hello">loading</include-fragment>'
document.body.appendChild(div)

return when(div.firstChild, 'include-fragment-replaced').then(() => {
assert.equal(document.querySelector('include-fragment'), null)
assert.equal(document.querySelector('#replaced').textContent, 'hello')
Expand Down Expand Up @@ -582,9 +581,11 @@ suite('include-fragment-element', function() {
}, 0)

return load
.then(() => when(div.firstChild, 'loadend'))
.then(() => when(div.firstChild, 'include-fragment-replaced'))
.then(() => {
assert.equal(count, 1, "Load occured too many times")
assert.equal(document.querySelector('include-fragment'), null)
assert.equal(document.querySelector('#replaced').textContent, 'hello')
})
})
})