gecko-dev/intl/l10n/DOMLocalization.jsm

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JavaScript

/* vim: set ts=2 et sw=2 tw=80 filetype=javascript: */
/* Copyright 2017 Mozilla Foundation and others
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* fluent-dom@0.2.0 */
const { Localization } =
ChromeUtils.import("resource://gre/modules/Localization.jsm", {});
// Match the opening angle bracket (<) in HTML tags, and HTML entities like
// &amp;, &#0038;, &#x0026;.
const reOverlay = /<|&#?\w+;/;
/**
* Elements allowed in translations even if they are not present in the source
* HTML. They are text-level elements as defined by the HTML5 spec:
* https://www.w3.org/TR/html5/text-level-semantics.html with the exception of:
*
* - a - because we don't allow href on it anyways,
* - ruby, rt, rp - because we don't allow nested elements to be inserted.
*/
const TEXT_LEVEL_ELEMENTS = {
"http://www.w3.org/1999/xhtml": [
"em", "strong", "small", "s", "cite", "q", "dfn", "abbr", "data",
"time", "code", "var", "samp", "kbd", "sub", "sup", "i", "b", "u",
"mark", "bdi", "bdo", "span", "br", "wbr"
],
};
const LOCALIZABLE_ATTRIBUTES = {
"http://www.w3.org/1999/xhtml": {
global: ["title", "aria-label", "aria-valuetext", "aria-moz-hint"],
a: ["download"],
area: ["download", "alt"],
// value is special-cased in isAttrNameLocalizable
input: ["alt", "placeholder"],
menuitem: ["label"],
menu: ["label"],
optgroup: ["label"],
option: ["label"],
track: ["label"],
img: ["alt"],
textarea: ["placeholder"],
th: ["abbr"]
},
"http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul": {
global: [
"accesskey", "aria-label", "aria-valuetext", "aria-moz-hint", "label"
],
key: ["key", "keycode"],
textbox: ["placeholder"],
toolbarbutton: ["tooltiptext"],
}
};
/**
* Translate an element.
*
* Translate the element's text content and attributes. Some HTML markup is
* allowed in the translation. The element's children with the data-l10n-name
* attribute will be treated as arguments to the translation. If the
* translation defines the same children, their attributes and text contents
* will be used for translating the matching source child.
*
* @param {Element} element
* @param {Object} translation
* @private
*/
function translateElement(element, translation) {
const {value} = translation;
if (typeof value === "string") {
if (!reOverlay.test(value)) {
// If the translation doesn't contain any markup skip the overlay logic.
element.textContent = value;
} else {
// Else parse the translation's HTML using an inert template element,
// sanitize it and replace the element's content.
const templateElement = element.ownerDocument.createElementNS(
"http://www.w3.org/1999/xhtml", "template"
);
// eslint-disable-next-line no-unsanitized/property
templateElement.innerHTML = value;
overlayChildNodes(templateElement.content, element);
}
}
// Even if the translation doesn't define any localizable attributes, run
// overlayAttributes to remove any localizable attributes set by previous
// translations.
overlayAttributes(translation, element);
}
/**
* Replace child nodes of an element with child nodes of another element.
*
* The contents of the target element will be cleared and fully replaced with
* sanitized contents of the source element.
*
* @param {DocumentFragment} fromFragment - The source of children to overlay.
* @param {Element} toElement - The target of the overlay.
* @private
*/
function overlayChildNodes(fromFragment, toElement) {
for (const childNode of fromFragment.childNodes) {
if (childNode.nodeType === childNode.TEXT_NODE) {
// Keep the translated text node.
continue;
}
if (childNode.hasAttribute("data-l10n-name")) {
const sanitized = namedChildFrom(toElement, childNode);
fromFragment.replaceChild(sanitized, childNode);
continue;
}
if (isElementAllowed(childNode)) {
const sanitized = allowedChild(childNode);
fromFragment.replaceChild(sanitized, childNode);
continue;
}
console.warn(
`An element of forbidden type "${childNode.localName}" was found in ` +
"the translation. Only safe text-level elements and elements with " +
"data-l10n-name are allowed."
);
// If all else fails, replace the element with its text content.
fromFragment.replaceChild(textNode(childNode), childNode);
}
toElement.textContent = "";
toElement.appendChild(fromFragment);
}
/**
* Transplant localizable attributes of an element to another element.
*
* Any localizable attributes already set on the target element will be
* cleared.
*
* @param {Element|Object} fromElement - The source of child nodes to overlay.
* @param {Element} toElement - The target of the overlay.
* @private
*/
function overlayAttributes(fromElement, toElement) {
const explicitlyAllowed = toElement.hasAttribute("data-l10n-attrs")
? toElement.getAttribute("data-l10n-attrs")
.split(",").map(i => i.trim())
: null;
// Remove existing localizable attributes.
for (const attr of Array.from(toElement.attributes)) {
if (isAttrNameLocalizable(attr.name, toElement, explicitlyAllowed)) {
toElement.removeAttribute(attr.name);
}
}
// fromElement might be a {value, attributes} object as returned by
// Localization.messageFromContext. In which case attributes may be null to
// save GC cycles.
if (!fromElement.attributes) {
return;
}
// Set localizable attributes.
for (const attr of Array.from(fromElement.attributes)) {
if (isAttrNameLocalizable(attr.name, toElement, explicitlyAllowed)) {
toElement.setAttribute(attr.name, attr.value);
}
}
}
/**
* Sanitize a child element created by the translation.
*
* Try to find a corresponding child in sourceElement and use it as the base
* for the sanitization. This will preserve functional attribtues defined on
* the child element in the source HTML.
*
* @param {Element} sourceElement - The source for data-l10n-name lookups.
* @param {Element} translatedChild - The translated child to be sanitized.
* @returns {Element}
* @private
*/
function namedChildFrom(sourceElement, translatedChild) {
const childName = translatedChild.getAttribute("data-l10n-name");
const sourceChild = sourceElement.querySelector(
`[data-l10n-name="${childName}"]`
);
if (!sourceChild) {
console.warn(
`An element named "${childName}" wasn't found in the source.`
);
return textNode(translatedChild);
}
if (sourceChild.localName !== translatedChild.localName) {
console.warn(
`An element named "${childName}" was found in the translation ` +
`but its type ${translatedChild.localName} didn't match the ` +
`element found in the source (${sourceChild.localName}).`
);
return textNode(translatedChild);
}
// Remove it from sourceElement so that the translation cannot use
// the same reference name again.
sourceElement.removeChild(sourceChild);
// We can't currently guarantee that a translation won't remove
// sourceChild from the element completely, which could break the app if
// it relies on an event handler attached to the sourceChild. Let's make
// this limitation explicit for now by breaking the identitiy of the
// sourceChild by cloning it. This will destroy all event handlers
// attached to sourceChild via addEventListener and via on<name>
// properties.
const clone = sourceChild.cloneNode(false);
return shallowPopulateUsing(translatedChild, clone);
}
/**
* Sanitize an allowed element.
*
* Text-level elements allowed in translations may only use safe attributes
* and will have any nested markup stripped to text content.
*
* @param {Element} element - The element to be sanitized.
* @returns {Element}
* @private
*/
function allowedChild(element) {
// Start with an empty element of the same type to remove nested children
// and non-localizable attributes defined by the translation.
const clone = element.ownerDocument.createElement(element.localName);
return shallowPopulateUsing(element, clone);
}
/**
* Convert an element to a text node.
*
* @param {Element} element - The element to be sanitized.
* @returns {Node}
* @private
*/
function textNode(element) {
return element.ownerDocument.createTextNode(element.textContent);
}
/**
* Check if element is allowed in the translation.
*
* This method is used by the sanitizer when the translation markup contains
* an element which is not present in the source code.
*
* @param {Element} element
* @returns {boolean}
* @private
*/
function isElementAllowed(element) {
const allowed = TEXT_LEVEL_ELEMENTS[element.namespaceURI];
return allowed && allowed.includes(element.localName);
}
/**
* Check if attribute is allowed for the given element.
*
* This method is used by the sanitizer when the translation markup contains
* DOM attributes, or when the translation has traits which map to DOM
* attributes.
*
* `explicitlyAllowed` can be passed as a list of attributes explicitly
* allowed on this element.
*
* @param {string} name
* @param {Element} element
* @param {Array} explicitlyAllowed
* @returns {boolean}
* @private
*/
function isAttrNameLocalizable(name, element, explicitlyAllowed = null) {
if (explicitlyAllowed && explicitlyAllowed.includes(name)) {
return true;
}
const allowed = LOCALIZABLE_ATTRIBUTES[element.namespaceURI];
if (!allowed) {
return false;
}
const attrName = name.toLowerCase();
const elemName = element.localName;
// Is it a globally safe attribute?
if (allowed.global.includes(attrName)) {
return true;
}
// Are there no allowed attributes for this element?
if (!allowed[elemName]) {
return false;
}
// Is it allowed on this element?
if (allowed[elemName].includes(attrName)) {
return true;
}
// Special case for value on HTML inputs with type button, reset, submit
if (element.namespaceURI === "http://www.w3.org/1999/xhtml" &&
elemName === "input" && attrName === "value") {
const type = element.type.toLowerCase();
if (type === "submit" || type === "button" || type === "reset") {
return true;
}
}
return false;
}
/**
* Helper to set textContent and localizable attributes on an element.
*
* @param {Element} fromElement
* @param {Element} toElement
* @returns {Element}
* @private
*/
function shallowPopulateUsing(fromElement, toElement) {
toElement.textContent = fromElement.textContent;
overlayAttributes(fromElement, toElement);
return toElement;
}
/**
* Sanitizes a translation before passing them to Node.localize API.
*
* It returns `false` if the translation contains DOM Overlays and should
* not go into Node.localize.
*
* Note: There's a third item of work that JS DOM Overlays do - removal
* of attributes from the previous translation.
* This is not trivial to implement for Node.localize scenario, so
* at the moment it is not supported.
*
* @param {{
* localName: string,
* namespaceURI: string,
* type: string || null
* l10nId: string,
* l10nArgs: Array<Object> || null,
* l10nAttrs: string ||null,
* }} l10nItems
* @param {{value: string, attrs: Object}} translations
* @returns boolean
* @private
*/
function sanitizeTranslationForNodeLocalize(l10nItem, translation) {
if (reOverlay.test(translation.value)) {
return false;
}
if (translation.attributes) {
const explicitlyAllowed = l10nItem.l10nAttrs === null ? null :
l10nItem.l10nAttrs.split(",").map(i => i.trim());
for (const [j, {name}] of translation.attributes.entries()) {
if (!isAttrNameLocalizable(name, l10nItem, explicitlyAllowed)) {
translation.attributes.splice(j, 1);
}
}
}
return true;
}
const L10NID_ATTR_NAME = "data-l10n-id";
const L10NARGS_ATTR_NAME = "data-l10n-args";
const L10N_ELEMENT_QUERY = `[${L10NID_ATTR_NAME}]`;
/**
* The `DOMLocalization` class is responsible for fetching resources and
* formatting translations.
*
* It implements the fallback strategy in case of errors encountered during the
* formatting of translations and methods for observing DOM
* trees with a `MutationObserver`.
*/
class DOMLocalization extends Localization {
/**
* @param {Window} windowElement
* @param {Array<String>} resourceIds - List of resource IDs
* @param {Function} generateMessages - Function that returns a
* generator over MessageContexts
* @returns {DOMLocalization}
*/
constructor(windowElement, resourceIds, generateMessages) {
super(resourceIds, generateMessages);
// A Set of DOM trees observed by the `MutationObserver`.
this.roots = new Set();
// requestAnimationFrame handler.
this.pendingrAF = null;
// list of elements pending for translation.
this.pendingElements = new Set();
this.windowElement = windowElement;
this.mutationObserver = new windowElement.MutationObserver(
mutations => this.translateMutations(mutations)
);
this.observerConfig = {
attribute: true,
characterData: false,
childList: true,
subtree: true,
attributeFilter: [L10NID_ATTR_NAME, L10NARGS_ATTR_NAME]
};
}
onChange() {
super.onChange();
this.translateRoots();
}
/**
* Set the `data-l10n-id` and `data-l10n-args` attributes on DOM elements.
* FluentDOM makes use of mutation observers to detect changes
* to `data-l10n-*` attributes and translate elements asynchronously.
* `setAttributes` is a convenience method which allows to translate
* DOM elements declaratively.
*
* You should always prefer to use `data-l10n-id` on elements (statically in
* HTML or dynamically via `setAttributes`) over manually retrieving
* translations with `format`. The use of attributes ensures that the
* elements can be retranslated when the user changes their language
* preferences.
*
* ```javascript
* localization.setAttributes(
* document.querySelector('#welcome'), 'hello', { who: 'world' }
* );
* ```
*
* This will set the following attributes on the `#welcome` element.
* The MutationObserver will pick up this change and will localize the element
* asynchronously.
*
* ```html
* <p id='welcome'
* data-l10n-id='hello'
* data-l10n-args='{"who": "world"}'>
* </p>
* ```
*
* @param {Element} element - Element to set attributes on
* @param {string} id - l10n-id string
* @param {Object<string, string>} args - KVP list of l10n arguments
* @returns {Element}
*/
setAttributes(element, id, args) {
element.setAttribute(L10NID_ATTR_NAME, id);
if (args) {
element.setAttribute(L10NARGS_ATTR_NAME, JSON.stringify(args));
} else {
element.removeAttribute(L10NARGS_ATTR_NAME);
}
return element;
}
/**
* Get the `data-l10n-*` attributes from DOM elements.
*
* ```javascript
* localization.getAttributes(
* document.querySelector('#welcome')
* );
* // -> { id: 'hello', args: { who: 'world' } }
* ```
*
* @param {Element} element - HTML element
* @returns {{id: string, args: Object}}
*/
getAttributes(element) {
return {
id: element.getAttribute(L10NID_ATTR_NAME),
args: JSON.parse(element.getAttribute(L10NARGS_ATTR_NAME) || null)
};
}
/**
* Add `newRoot` to the list of roots managed by this `DOMLocalization`.
*
* Additionally, if this `DOMLocalization` has an observer, start observing
* `newRoot` in order to translate mutations in it.
*
* @param {Element} newRoot - Root to observe.
*/
connectRoot(newRoot) {
for (const root of this.roots) {
if (root === newRoot ||
root.contains(newRoot) ||
newRoot.contains(root)) {
throw new Error("Cannot add a root that overlaps with existing root.");
}
}
this.roots.add(newRoot);
this.mutationObserver.observe(newRoot, this.observerConfig);
}
/**
* Remove `root` from the list of roots managed by this `DOMLocalization`.
*
* Additionally, if this `DOMLocalization` has an observer, stop observing
* `root`.
*
* Returns `true` if the root was the last one managed by this
* `DOMLocalization`.
*
* @param {Element} root - Root to disconnect.
* @returns {boolean}
*/
disconnectRoot(root) {
this.roots.delete(root);
// Pause and resume the mutation observer to stop observing `root`.
this.pauseObserving();
this.resumeObserving();
return this.roots.size === 0;
}
/**
* Translate all roots associated with this `DOMLocalization`.
*
* @returns {Promise}
*/
translateRoots() {
const roots = Array.from(this.roots);
return Promise.all(
roots.map(root => this.translateFragment(root))
);
}
/**
* Pauses the `MutationObserver`.
*
* @private
*/
pauseObserving() {
this.translateMutations(this.mutationObserver.takeRecords());
this.mutationObserver.disconnect();
}
/**
* Resumes the `MutationObserver`.
*
* @private
*/
resumeObserving() {
for (const root of this.roots) {
this.mutationObserver.observe(root, this.observerConfig);
}
}
/**
* Translate mutations detected by the `MutationObserver`.
*
* @private
*/
translateMutations(mutations) {
for (const mutation of mutations) {
switch (mutation.type) {
case "attributes":
if (mutation.target.hasAttribute("data-l10n-id")) {
this.pendingElements.add(mutation.target);
}
break;
case "childList":
for (const addedNode of mutation.addedNodes) {
if (addedNode.nodeType === addedNode.ELEMENT_NODE) {
if (addedNode.childElementCount) {
for (const element of this.getTranslatables(addedNode)) {
this.pendingElements.add(element);
}
} else if (addedNode.hasAttribute(L10NID_ATTR_NAME)) {
this.pendingElements.add(addedNode);
}
}
}
break;
}
}
// This fragment allows us to coalesce all pending translations
// into a single requestAnimationFrame.
if (this.pendingElements.size > 0) {
if (this.pendingrAF === null) {
this.pendingrAF = this.windowElement.requestAnimationFrame(() => {
// We need to filter for elements that lost their l10n-id while
// waiting for the animation frame.
this.translateElements(Array.from(this.pendingElements)
.filter(elem => elem.hasAttribute("data-l10n-id")));
this.pendingElements.clear();
this.pendingrAF = null;
});
}
}
}
/**
* Translate a DOM element or fragment asynchronously using this
* `DOMLocalization` object.
*
* Manually trigger the translation (or re-translation) of a DOM fragment.
* Use the `data-l10n-id` and `data-l10n-args` attributes to mark up the DOM
* with information about which translations to use.
*
* Returns a `Promise` that gets resolved once the translation is complete.
*
* @param {DOMFragment} frag - Element or DocumentFragment to be translated
* @returns {Promise}
*/
translateFragment(frag) {
if (frag.localize) {
// This is a temporary fast-path offered by Gecko to workaround performance
// issues coming from Fluent and XBL+Stylo performing unnecesary
// operations during startup.
// For details see bug 1441037, bug 1442262, and bug 1363862.
// A sparse array which will store translations separated out from
// all translations that is needed for DOM Overlay.
const overlayTranslations = [];
const getTranslationsForItems = async l10nItems => {
const keys = l10nItems.map(
l10nItem => ({id: l10nItem.l10nId, args: l10nItem.l10nArgs}));
const translations = await this.formatMessages(keys);
// Here we want to separate out elements that require DOM Overlays.
// Those elements will have to be translated using our JS
// implementation, while everything else is going to use the fast-path.
for (const [i, translation] of translations.entries()) {
if (translation === undefined) {
continue;
}
const hasOnlyText =
sanitizeTranslationForNodeLocalize(l10nItems[i], translation);
if (!hasOnlyText) {
// Removing from translations to make Node.localize skip it.
// We will translate it below using JS DOM Overlays.
overlayTranslations[i] = translations[i];
translations[i] = undefined;
}
}
// We pause translation observing here because Node.localize
// will translate the whole DOM next, using the `translations`.
//
// The observer will be resumed after DOM Overlays are localized
// in the next microtask.
this.pauseObserving();
return translations;
};
return frag.localize(getTranslationsForItems.bind(this))
.then(untranslatedElements => {
for (let i = 0; i < overlayTranslations.length; i++) {
if (overlayTranslations[i] !== undefined &&
untranslatedElements[i] !== undefined) {
translateElement(untranslatedElements[i], overlayTranslations[i]);
}
}
this.resumeObserving();
})
.catch(e => {
this.resumeObserving();
throw e;
});
}
return this.translateElements(this.getTranslatables(frag));
}
/**
* Translate a list of DOM elements asynchronously using this
* `DOMLocalization` object.
*
* Manually trigger the translation (or re-translation) of a list of elements.
* Use the `data-l10n-id` and `data-l10n-args` attributes to mark up the DOM
* with information about which translations to use.
*
* Returns a `Promise` that gets resolved once the translation is complete.
*
* @param {Array<Element>} elements - List of elements to be translated
* @returns {Promise}
*/
async translateElements(elements) {
if (!elements.length) {
return undefined;
}
const keys = elements.map(this.getKeysForElement);
const translations = await this.formatMessages(keys);
return this.applyTranslations(elements, translations);
}
/**
* Applies translations onto elements.
*
* @param {Array<Element>} elements
* @param {Array<Object>} translations
* @private
*/
applyTranslations(elements, translations) {
this.pauseObserving();
for (let i = 0; i < elements.length; i++) {
if (translations[i] !== undefined) {
translateElement(elements[i], translations[i]);
}
}
this.resumeObserving();
}
/**
* Collects all translatable child elements of the element.
*
* @param {Element} element
* @returns {Array<Element>}
* @private
*/
getTranslatables(element) {
const nodes = Array.from(element.querySelectorAll(L10N_ELEMENT_QUERY));
if (typeof element.hasAttribute === "function" &&
element.hasAttribute(L10NID_ATTR_NAME)) {
nodes.push(element);
}
return nodes;
}
/**
* Get the `data-l10n-*` attributes from DOM elements as a two-element
* array.
*
* @param {Element} element
* @returns {Object}
* @private
*/
getKeysForElement(element) {
return {
id: element.getAttribute(L10NID_ATTR_NAME),
args: JSON.parse(element.getAttribute(L10NARGS_ATTR_NAME) || null)
};
}
}
this.DOMLocalization = DOMLocalization;
var EXPORTED_SYMBOLS = ["DOMLocalization"];