@polymer/lit-element/lib/updating-element.js

/**
 * @license
 * Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at
 * http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at
 * http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at
 * http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at
 * http://polymer.github.io/PATENTS.txt
 */
/**
 * When using Closure Compiler, JSCompiler_renameProperty(property, object) is
 * replaced at compile time by the munged name for object[property]. We cannot
 * alias this function, so we have to use a small shim that has the same
 * behavior when not compiling.
 */
const JSCompiler_renameProperty = (prop, _obj) => prop;
/**
 * Returns the property descriptor for a property on this prototype by walking
 * up the prototype chain. Note that we stop just before Object.prototype, which
 * also avoids issues with Symbol polyfills (core-js, get-own-property-symbols),
 * which create accessors for the symbols on Object.prototype.
 */
const descriptorFromPrototype = (name, proto) => {
    if (name in proto) {
        while (proto !== Object.prototype) {
            if (proto.hasOwnProperty(name)) {
                return Object.getOwnPropertyDescriptor(proto, name);
            }
            proto = Object.getPrototypeOf(proto);
        }
    }
    return undefined;
};
export const defaultConverter = {
    toAttribute(value, type) {
        switch (type) {
            case Boolean:
                return value ? '' : null;
            case Object:
            case Array:
                // if the value is `null` or `undefined` pass this through
                // to allow removing/no change behavior.
                return value == null ? value : JSON.stringify(value);
        }
        return value;
    },
    fromAttribute(value, type) {
        switch (type) {
            case Boolean:
                return value !== null;
            case Number:
                return value === null ? null : Number(value);
            case Object:
            case Array:
                return JSON.parse(value);
        }
        return value;
    }
};
/**
 * Change function that returns true if `value` is different from `oldValue`.
 * This method is used as the default for a property's `hasChanged` function.
 */
export const notEqual = (value, old) => {
    // This ensures (old==NaN, value==NaN) always returns false
    return old !== value && (old === old || value === value);
};
const defaultPropertyDeclaration = {
    attribute: true,
    type: String,
    converter: defaultConverter,
    reflect: false,
    hasChanged: notEqual
};
const microtaskPromise = Promise.resolve(true);
const STATE_HAS_UPDATED = 1;
const STATE_UPDATE_REQUESTED = 1 << 2;
const STATE_IS_REFLECTING_TO_ATTRIBUTE = 1 << 3;
const STATE_IS_REFLECTING_TO_PROPERTY = 1 << 4;
const STATE_HAS_CONNECTED = 1 << 5;
/**
 * Base element class which manages element properties and attributes. When
 * properties change, the `update` method is asynchronously called. This method
 * should be supplied by subclassers to render updates as desired.
 */
export class UpdatingElement extends HTMLElement {
    constructor() {
        super();
        this._updateState = 0;
        this._instanceProperties = undefined;
        this._updatePromise = microtaskPromise;
        this._hasConnectedResolver = undefined;
        /**
         * Map with keys for any properties that have changed since the last
         * update cycle with previous values.
         */
        this._changedProperties = new Map();
        /**
         * Map with keys of properties that should be reflected when updated.
         */
        this._reflectingProperties = undefined;
        this.initialize();
    }
    /**
     * Returns a list of attributes corresponding to the registered properties.
     * @nocollapse
     */
    static get observedAttributes() {
        // note: piggy backing on this to ensure we're _finalized.
        this._finalize();
        const attributes = [];
        for (const [p, v] of this._classProperties) {
            const attr = this._attributeNameForProperty(p, v);
            if (attr !== undefined) {
                this._attributeToPropertyMap.set(attr, p);
                attributes.push(attr);
            }
        }
        return attributes;
    }
    /**
     * Ensures the private `_classProperties` property metadata is created.
     * In addition to `_finalize` this is also called in `createProperty` to
     * ensure the `@property` decorator can add property metadata.
     */
    /** @nocollapse */
    static _ensureClassProperties() {
        // ensure private storage for property declarations.
        if (!this.hasOwnProperty(JSCompiler_renameProperty('_classProperties', this))) {
            this._classProperties = new Map();
            // NOTE: Workaround IE11 not supporting Map constructor argument.
            const superProperties = Object.getPrototypeOf(this)._classProperties;
            if (superProperties !== undefined) {
                superProperties.forEach((v, k) => this._classProperties.set(k, v));
            }
        }
    }
    /**
     * Creates a property accessor on the element prototype if one does not exist.
     * The property setter calls the property's `hasChanged` property option
     * or uses a strict identity check to determine whether or not to request
     * an update.
     * @nocollapse
     */
    static createProperty(name, options = defaultPropertyDeclaration) {
        // Note, since this can be called by the `@property` decorator which
        // is called before `_finalize`, we ensure storage exists for property
        // metadata.
        this._ensureClassProperties();
        this._classProperties.set(name, options);
        if (!options.noAccessor) {
            const superDesc = descriptorFromPrototype(name, this.prototype);
            let desc;
            // If there is a super accessor, capture it and "super" to it
            if (superDesc !== undefined && (superDesc.set && superDesc.get)) {
                const { set, get } = superDesc;
                desc = {
                    get() { return get.call(this); },
                    set(value) {
                        const oldValue = this[name];
                        set.call(this, value);
                        this.requestUpdate(name, oldValue);
                    },
                    configurable: true,
                    enumerable: true
                };
            }
            else {
                const key = typeof name === 'symbol' ? Symbol() : `__${name}`;
                desc = {
                    get() { return this[key]; },
                    set(value) {
                        const oldValue = this[name];
                        this[key] = value;
                        this.requestUpdate(name, oldValue);
                    },
                    configurable: true,
                    enumerable: true
                };
            }
            Object.defineProperty(this.prototype, name, desc);
        }
    }
    /**
     * Creates property accessors for registered properties and ensures
     * any superclasses are also finalized.
     * @nocollapse
     */
    static _finalize() {
        if (this.hasOwnProperty(JSCompiler_renameProperty('finalized', this)) &&
            this.finalized) {
            return;
        }
        // finalize any superclasses
        const superCtor = Object.getPrototypeOf(this);
        if (typeof superCtor._finalize === 'function') {
            superCtor._finalize();
        }
        this.finalized = true;
        this._ensureClassProperties();
        // initialize Map populated in observedAttributes
        this._attributeToPropertyMap = new Map();
        // make any properties
        // Note, only process "own" properties since this element will inherit
        // any properties defined on the superClass, and finalization ensures
        // the entire prototype chain is finalized.
        if (this.hasOwnProperty(JSCompiler_renameProperty('properties', this))) {
            const props = this.properties;
            // support symbols in properties (IE11 does not support this)
            const propKeys = [
                ...Object.getOwnPropertyNames(props),
                ...(typeof Object.getOwnPropertySymbols === 'function')
                    ? Object.getOwnPropertySymbols(props)
                    : []
            ];
            for (const p of propKeys) {
                // note, use of `any` is due to TypeSript lack of support for symbol in
                // index types
                this.createProperty(p, props[p]);
            }
        }
    }
    /**
     * Returns the property name for the given attribute `name`.
     * @nocollapse
     */
    static _attributeNameForProperty(name, options) {
        const attribute = options.attribute;
        return attribute === false
            ? undefined
            : (typeof attribute === 'string'
                ? attribute
                : (typeof name === 'string' ? name.toLowerCase()
                    : undefined));
    }
    /**
     * Returns true if a property should request an update.
     * Called when a property value is set and uses the `hasChanged`
     * option for the property if present or a strict identity check.
     * @nocollapse
     */
    static _valueHasChanged(value, old, hasChanged = notEqual) {
        return hasChanged(value, old);
    }
    /**
     * Returns the property value for the given attribute value.
     * Called via the `attributeChangedCallback` and uses the property's
     * `converter` or `converter.fromAttribute` property option.
     * @nocollapse
     */
    static _propertyValueFromAttribute(value, options) {
        const type = options.type;
        const converter = options.converter || defaultConverter;
        const fromAttribute = (typeof converter === 'function' ? converter : converter.fromAttribute);
        return fromAttribute ? fromAttribute(value, type) : value;
    }
    /**
     * Returns the attribute value for the given property value. If this
     * returns undefined, the property will *not* be reflected to an attribute.
     * If this returns null, the attribute will be removed, otherwise the
     * attribute will be set to the value.
     * This uses the property's `reflect` and `type.toAttribute` property options.
     * @nocollapse
     */
    static _propertyValueToAttribute(value, options) {
        if (options.reflect === undefined) {
            return;
        }
        const type = options.type;
        const converter = options.converter;
        const toAttribute = converter && converter.toAttribute ||
            defaultConverter.toAttribute;
        return toAttribute(value, type);
    }
    /**
     * Performs element initialization. By default captures any pre-set values for
     * registered properties.
     */
    initialize() { this._saveInstanceProperties(); }
    /**
     * Fixes any properties set on the instance before upgrade time.
     * Otherwise these would shadow the accessor and break these properties.
     * The properties are stored in a Map which is played back after the
     * constructor runs. Note, on very old versions of Safari (<=9) or Chrome
     * (<=41), properties created for native platform properties like (`id` or
     * `name`) may not have default values set in the element constructor. On
     * these browsers native properties appear on instances and therefore their
     * default value will overwrite any element default (e.g. if the element sets
     * this.id = 'id' in the constructor, the 'id' will become '' since this is
     * the native platform default).
     */
    _saveInstanceProperties() {
        for (const [p] of this.constructor
            ._classProperties) {
            if (this.hasOwnProperty(p)) {
                const value = this[p];
                delete this[p];
                if (!this._instanceProperties) {
                    this._instanceProperties = new Map();
                }
                this._instanceProperties.set(p, value);
            }
        }
    }
    /**
     * Applies previously saved instance properties.
     */
    _applyInstanceProperties() {
        for (const [p, v] of this._instanceProperties) {
            this[p] = v;
        }
        this._instanceProperties = undefined;
    }
    connectedCallback() {
        this._updateState = this._updateState | STATE_HAS_CONNECTED;
        // Ensure connection triggers an update. Updates cannot complete before
        // connection and if one is pending connection the `_hasConnectionResolver`
        // will exist. If so, resolve it to complete the update, otherwise
        // requestUpdate.
        if (this._hasConnectedResolver) {
            this._hasConnectedResolver();
            this._hasConnectedResolver = undefined;
        }
        else {
            this.requestUpdate();
        }
    }
    /**
     * Allows for `super.disconnectedCallback()` in extensions while
     * reserving the possibility of making non-breaking feature additions
     * when disconnecting at some point in the future.
     */
    disconnectedCallback() { }
    /**
     * Synchronizes property values when attributes change.
     */
    attributeChangedCallback(name, old, value) {
        if (old !== value) {
            this._attributeToProperty(name, value);
        }
    }
    _propertyToAttribute(name, value, options = defaultPropertyDeclaration) {
        const ctor = this.constructor;
        const attr = ctor._attributeNameForProperty(name, options);
        if (attr !== undefined) {
            const attrValue = ctor._propertyValueToAttribute(value, options);
            // an undefined value does not change the attribute.
            if (attrValue === undefined) {
                return;
            }
            // Track if the property is being reflected to avoid
            // setting the property again via `attributeChangedCallback`. Note:
            // 1. this takes advantage of the fact that the callback is synchronous.
            // 2. will behave incorrectly if multiple attributes are in the reaction
            // stack at time of calling. However, since we process attributes
            // in `update` this should not be possible (or an extreme corner case
            // that we'd like to discover).
            // mark state reflecting
            this._updateState = this._updateState | STATE_IS_REFLECTING_TO_ATTRIBUTE;
            if (attrValue == null) {
                this.removeAttribute(attr);
            }
            else {
                this.setAttribute(attr, attrValue);
            }
            // mark state not reflecting
            this._updateState = this._updateState & ~STATE_IS_REFLECTING_TO_ATTRIBUTE;
        }
    }
    _attributeToProperty(name, value) {
        // Use tracking info to avoid deserializing attribute value if it was
        // just set from a property setter.
        if (this._updateState & STATE_IS_REFLECTING_TO_ATTRIBUTE) {
            return;
        }
        const ctor = this.constructor;
        const propName = ctor._attributeToPropertyMap.get(name);
        if (propName !== undefined) {
            const options = ctor._classProperties.get(propName) || defaultPropertyDeclaration;
            // mark state reflecting
            this._updateState = this._updateState | STATE_IS_REFLECTING_TO_PROPERTY;
            this[propName] =
                ctor._propertyValueFromAttribute(value, options);
            // mark state not reflecting
            this._updateState = this._updateState & ~STATE_IS_REFLECTING_TO_PROPERTY;
        }
    }
    /**
     * Requests an update which is processed asynchronously. This should
     * be called when an element should update based on some state not triggered
     * by setting a property. In this case, pass no arguments. It should also be
     * called when manually implementing a property setter. In this case, pass the
     * property `name` and `oldValue` to ensure that any configured property
     * options are honored. Returns the `updateComplete` Promise which is resolved
     * when the update completes.
     *
     * @param name {PropertyKey} (optional) name of requesting property
     * @param oldValue {any} (optional) old value of requesting property
     * @returns {Promise} A Promise that is resolved when the update completes.
     */
    requestUpdate(name, oldValue) {
        let shouldRequestUpdate = true;
        // if we have a property key, perform property update steps.
        if (name !== undefined && !this._changedProperties.has(name)) {
            const ctor = this.constructor;
            const options = ctor._classProperties.get(name) || defaultPropertyDeclaration;
            if (ctor._valueHasChanged(this[name], oldValue, options.hasChanged)) {
                // track old value when changing.
                this._changedProperties.set(name, oldValue);
                // add to reflecting properties set
                if (options.reflect === true &&
                    !(this._updateState & STATE_IS_REFLECTING_TO_PROPERTY)) {
                    if (this._reflectingProperties === undefined) {
                        this._reflectingProperties = new Map();
                    }
                    this._reflectingProperties.set(name, options);
                }
                // abort the request if the property should not be considered changed.
            }
            else {
                shouldRequestUpdate = false;
            }
        }
        if (!this._hasRequestedUpdate && shouldRequestUpdate) {
            this._enqueueUpdate();
        }
        return this.updateComplete;
    }
    /**
     * Sets up the element to asynchronously update.
     */
    async _enqueueUpdate() {
        // Mark state updating...
        this._updateState = this._updateState | STATE_UPDATE_REQUESTED;
        let resolve;
        const previousUpdatePromise = this._updatePromise;
        this._updatePromise = new Promise((res) => resolve = res);
        // Ensure any previous update has resolved before updating.
        // This `await` also ensures that property changes are batched.
        await previousUpdatePromise;
        // Make sure the element has connected before updating.
        if (!this._hasConnected) {
            await new Promise((res) => this._hasConnectedResolver = res);
        }
        // Allow `performUpdate` to be asynchronous to enable scheduling of updates.
        const result = this.performUpdate();
        // Note, this is to avoid delaying an additional microtask unless we need
        // to.
        if (result != null &&
            typeof result.then === 'function') {
            await result;
        }
        resolve(!this._hasRequestedUpdate);
    }
    get _hasConnected() {
        return (this._updateState & STATE_HAS_CONNECTED);
    }
    get _hasRequestedUpdate() {
        return (this._updateState & STATE_UPDATE_REQUESTED);
    }
    get hasUpdated() { return (this._updateState & STATE_HAS_UPDATED); }
    /**
     * Performs an element update.
     *
     * You can override this method to change the timing of updates. For instance,
     * to schedule updates to occur just before the next frame:
     *
     * ```
     * protected async performUpdate(): Promise<unknown> {
     *   await new Promise((resolve) => requestAnimationFrame(() => resolve()));
     *   super.performUpdate();
     * }
     * ```
     */
    performUpdate() {
        // Mixin instance properties once, if they exist.
        if (this._instanceProperties) {
            this._applyInstanceProperties();
        }
        if (this.shouldUpdate(this._changedProperties)) {
            const changedProperties = this._changedProperties;
            this.update(changedProperties);
            this._markUpdated();
            if (!(this._updateState & STATE_HAS_UPDATED)) {
                this._updateState = this._updateState | STATE_HAS_UPDATED;
                this.firstUpdated(changedProperties);
            }
            this.updated(changedProperties);
        }
        else {
            this._markUpdated();
        }
    }
    _markUpdated() {
        this._changedProperties = new Map();
        this._updateState = this._updateState & ~STATE_UPDATE_REQUESTED;
    }
    /**
     * Returns a Promise that resolves when the element has completed updating.
     * The Promise value is a boolean that is `true` if the element completed the
     * update without triggering another update. The Promise result is `false` if
     * a property was set inside `updated()`. This getter can be implemented to
     * await additional state. For example, it is sometimes useful to await a
     * rendered element before fulfilling this Promise. To do this, first await
     * `super.updateComplete` then any subsequent state.
     *
     * @returns {Promise} The Promise returns a boolean that indicates if the
     * update resolved without triggering another update.
     */
    get updateComplete() { return this._updatePromise; }
    /**
     * Controls whether or not `update` should be called when the element requests
     * an update. By default, this method always returns `true`, but this can be
     * customized to control when to update.
     *
     * * @param _changedProperties Map of changed properties with old values
     */
    shouldUpdate(_changedProperties) {
        return true;
    }
    /**
     * Updates the element. This method reflects property values to attributes.
     * It can be overridden to render and keep updated element DOM.
     * Setting properties inside this method will *not* trigger
     * another update.
     *
     * * @param _changedProperties Map of changed properties with old values
     */
    update(_changedProperties) {
        if (this._reflectingProperties !== undefined &&
            this._reflectingProperties.size > 0) {
            for (const [k, v] of this._reflectingProperties) {
                this._propertyToAttribute(k, this[k], v);
            }
            this._reflectingProperties = undefined;
        }
    }
    /**
     * Invoked whenever the element is updated. Implement to perform
     * post-updating tasks via DOM APIs, for example, focusing an element.
     *
     * Setting properties inside this method will trigger the element to update
     * again after this update cycle completes.
     *
     * * @param _changedProperties Map of changed properties with old values
     */
    updated(_changedProperties) { }
    /**
     * Invoked when the element is first updated. Implement to perform one time
     * work on the element after update.
     *
     * Setting properties inside this method will trigger the element to update
     * again after this update cycle completes.
     *
     * * @param _changedProperties Map of changed properties with old values
     */
    firstUpdated(_changedProperties) { }
}
/**
 * Marks class as having finished creating properties.
 */
UpdatingElement.finalized = true;
//# sourceMappingURL=updating-element.js.map