/**
* @license
* Copyright 2017 Google LLC
* SPDX-License-Identifier: BSD-3-Clause
*/
/**
* Use this module if you want to create your own base class extending
* {@link ReactiveElement}.
* @packageDocumentation
*/
import { CSSResultGroup, CSSResultOrNative } from './css-tag.js';
import type { ReactiveController, ReactiveControllerHost } from './reactive-controller.js';
export * from './css-tag.js';
export type { ReactiveController, ReactiveControllerHost, } from './reactive-controller.js';
/**
* Contains types that are part of the unstable debug API.
*
* Everything in this API is not stable and may change or be removed in the future,
* even on patch releases.
*/
export declare namespace ReactiveUnstable {
/**
* When Lit is running in dev mode and `window.emitLitDebugLogEvents` is true,
* we will emit 'lit-debug' events to window, with live details about the update and render
* lifecycle. These can be useful for writing debug tooling and visualizations.
*
* Please be aware that running with window.emitLitDebugLogEvents has performance overhead,
* making certain operations that are normally very cheap (like a no-op render) much slower,
* because we must copy data and dispatch events.
*/
namespace DebugLog {
type Entry = Update;
interface Update {
kind: 'update';
}
}
}
/**
* Converts property values to and from attribute values.
*/
export interface ComplexAttributeConverter<Type = unknown, TypeHint = unknown> {
/**
* Called to convert an attribute value to a property
* value.
*/
fromAttribute?(value: string | null, type?: TypeHint): Type;
/**
* Called to convert a property value to an attribute
* value.
*
* It returns unknown instead of string, to be compatible with
* https://github.com/WICG/trusted-types (and similar efforts).
*/
toAttribute?(value: Type, type?: TypeHint): unknown;
}
type AttributeConverter<Type = unknown, TypeHint = unknown> = ComplexAttributeConverter<Type> | ((value: string | null, type?: TypeHint) => Type);
/**
* Defines options for a property accessor.
*/
export interface PropertyDeclaration<Type = unknown, TypeHint = unknown> {
/**
* When set to `true`, indicates the property is internal private state. The
* property should not be set by users. When using TypeScript, this property
* should be marked as `private` or `protected`, and it is also a common
* practice to use a leading `_` in the name. The property is not added to
* `observedAttributes`.
*/
readonly state?: boolean;
/**
* Indicates how and whether the property becomes an observed attribute.
* If the value is `false`, the property is not added to `observedAttributes`.
* If true or absent, the lowercased property name is observed (e.g. `fooBar`
* becomes `foobar`). If a string, the string value is observed (e.g
* `attribute: 'foo-bar'`).
*/
readonly attribute?: boolean | string;
/**
* Indicates the type of the property. This is used only as a hint for the
* `converter` to determine how to convert the attribute
* to/from a property.
*/
readonly type?: TypeHint;
/**
* Indicates how to convert the attribute to/from a property. If this value
* is a function, it is used to convert the attribute value a the property
* value. If it's an object, it can have keys for `fromAttribute` and
* `toAttribute`. If no `toAttribute` function is provided and
* `reflect` is set to `true`, the property value is set directly to the
* attribute. A default `converter` is used if none is provided; it supports
* `Boolean`, `String`, `Number`, `Object`, and `Array`. Note,
* when a property changes and the converter is used to update the attribute,
* the property is never updated again as a result of the attribute changing,
* and vice versa.
*/
readonly converter?: AttributeConverter<Type, TypeHint>;
/**
* Indicates if the property should reflect to an attribute.
* If `true`, when the property is set, the attribute is set using the
* attribute name determined according to the rules for the `attribute`
* property option and the value of the property converted using the rules
* from the `converter` property option.
*/
readonly reflect?: boolean;
/**
* A function that indicates if a property should be considered changed when
* it is set. The function should take the `newValue` and `oldValue` and
* return `true` if an update should be requested.
*/
hasChanged?(value: Type, oldValue: Type): boolean;
/**
* Indicates whether an accessor will be created for this property. By
* default, an accessor will be generated for this property that requests an
* update when set. If this flag is `true`, no accessor will be created, and
* it will be the user's responsibility to call
* `this.requestUpdate(propertyName, oldValue)` to request an update when
* the property changes.
*/
readonly noAccessor?: boolean;
}
/**
* Map of properties to PropertyDeclaration options. For each property an
* accessor is made, and the property is processed according to the
* PropertyDeclaration options.
*/
export interface PropertyDeclarations {
readonly [key: string]: PropertyDeclaration;
}
type PropertyDeclarationMap = Map<PropertyKey, PropertyDeclaration>;
/**
* A Map of property keys to values.
*
* Takes an optional type parameter T, which when specified as a non-any,
* non-unknown type, will make the Map more strongly-typed, associating the map
* keys with their corresponding value type on T.
*
* Use `PropertyValues<this>` when overriding ReactiveElement.update() and
* other lifecycle methods in order to get stronger type-checking on keys
* and values.
*/
export type PropertyValues<T = any> = T extends object ? PropertyValueMap<T> : Map<PropertyKey, unknown>;
/**
* Do not use, instead prefer {@linkcode PropertyValues}.
*/
export interface PropertyValueMap<T> extends Map<PropertyKey, unknown> {
get<K extends keyof T>(k: K): T[K] | undefined;
set<K extends keyof T>(key: K, value: T[K]): this;
has<K extends keyof T>(k: K): boolean;
delete<K extends keyof T>(k: K): boolean;
}
export declare const defaultConverter: ComplexAttributeConverter;
export interface HasChanged {
(value: unknown, old: unknown): boolean;
}
/**
* 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 declare const notEqual: HasChanged;
/**
* A string representing one of the supported dev mode warning categories.
*/
export type WarningKind = 'change-in-update' | 'migration' | 'async-perform-update';
export type Initializer = (element: ReactiveElement) => void;
declare global {
interface SymbolConstructor {
readonly metadata: unique symbol;
}
}
declare global {
var litPropertyMetadata: WeakMap<object, Map<PropertyKey, PropertyDeclaration>>;
}
/**
* Base element class which manages element properties and attributes. When
* properties change, the `update` method is asynchronously called. This method
* should be supplied by subclasses to render updates as desired.
* @noInheritDoc
*/
export declare abstract class ReactiveElement extends HTMLElement implements ReactiveControllerHost {
/**
* Read or set all the enabled warning categories for this class.
*
* This property is only used in development builds.
*
* @nocollapse
* @category dev-mode
*/
static enabledWarnings?: WarningKind[];
/**
* Enable the given warning category for this class.
*
* This method only exists in development builds, so it should be accessed
* with a guard like:
*
* ```ts
* // Enable for all ReactiveElement subclasses
* ReactiveElement.enableWarning?.('migration');
*
* // Enable for only MyElement and subclasses
* MyElement.enableWarning?.('migration');
* ```
*
* @nocollapse
* @category dev-mode
*/
static enableWarning?: (warningKind: WarningKind) => void;
/**
* Disable the given warning category for this class.
*
* This method only exists in development builds, so it should be accessed
* with a guard like:
*
* ```ts
* // Disable for all ReactiveElement subclasses
* ReactiveElement.disableWarning?.('migration');
*
* // Disable for only MyElement and subclasses
* MyElement.disableWarning?.('migration');
* ```
*
* @nocollapse
* @category dev-mode
*/
static disableWarning?: (warningKind: WarningKind) => void;
/**
* Adds an initializer function to the class that is called during instance
* construction.
*
* This is useful for code that runs against a `ReactiveElement`
* subclass, such as a decorator, that needs to do work for each
* instance, such as setting up a `ReactiveController`.
*
* ```ts
* const myDecorator = (target: typeof ReactiveElement, key: string) => {
* target.addInitializer((instance: ReactiveElement) => {
* // This is run during construction of the element
* new MyController(instance);
* });
* }
* ```
*
* Decorating a field will then cause each instance to run an initializer
* that adds a controller:
*
* ```ts
* class MyElement extends LitElement {
* @myDecorator foo;
* }
* ```
*
* Initializers are stored per-constructor. Adding an initializer to a
* subclass does not add it to a superclass. Since initializers are run in
* constructors, initializers will run in order of the class hierarchy,
* starting with superclasses and progressing to the instance's class.
*
* @nocollapse
*/
static addInitializer(initializer: Initializer): void;
static _initializers?: Initializer[];
/**
* Maps attribute names to properties; for example `foobar` attribute to
* `fooBar` property. Created lazily on user subclasses when finalizing the
* class.
* @nocollapse
*/
private static __attributeToPropertyMap;
/**
* Marks class as having been finalized, which includes creating properties
* from `static properties`, but does *not* include all properties created
* from decorators.
* @nocollapse
*/
protected static finalized: true | undefined;
/**
* Memoized list of all element properties, including any superclass
* properties. Created lazily on user subclasses when finalizing the class.
*
* @nocollapse
* @category properties
*/
static elementProperties: PropertyDeclarationMap;
/**
* User-supplied object that maps property names to `PropertyDeclaration`
* objects containing options for configuring reactive properties. When
* a reactive property is set the element will update and render.
*
* By default properties are public fields, and as such, they should be
* considered as primarily settable by element users, either via attribute or
* the property itself.
*
* Generally, properties that are changed by the element should be private or
* protected fields and should use the `state: true` option. Properties
* marked as `state` do not reflect from the corresponding attribute
*
* However, sometimes element code does need to set a public property. This
* should typically only be done in response to user interaction, and an event
* should be fired informing the user; for example, a checkbox sets its
* `checked` property when clicked and fires a `changed` event. Mutating
* public properties should typically not be done for non-primitive (object or
* array) properties. In other cases when an element needs to manage state, a
* private property set with the `state: true` option should be used. When
* needed, state properties can be initialized via public properties to
* facilitate complex interactions.
* @nocollapse
* @category properties
*/
static properties: PropertyDeclarations;
/**
* Memoized list of all element styles.
* Created lazily on user subclasses when finalizing the class.
* @nocollapse
* @category styles
*/
static elementStyles: Array<CSSResultOrNative>;
/**
* Array of styles to apply to the element. The styles should be defined
* using the {@linkcode css} tag function, via constructible stylesheets, or
* imported from native CSS module scripts.
*
* Note on Content Security Policy:
*
* Element styles are implemented with `<style>` tags when the browser doesn't
* support adopted StyleSheets. To use such `<style>` tags with the style-src
* CSP directive, the style-src value must either include 'unsafe-inline' or
* `nonce-<base64-value>` with `<base64-value>` replaced be a server-generated
* nonce.
*
* To provide a nonce to use on generated `<style>` elements, set
* `window.litNonce` to a server-generated nonce in your page's HTML, before
* loading application code:
*
* ```html
* <script>
* // Generated and unique per request:
* window.litNonce = 'a1b2c3d4';
* </script>
* ```
* @nocollapse
* @category styles
*/
static styles?: CSSResultGroup;
/**
* Returns a list of attributes corresponding to the registered properties.
* @nocollapse
* @category attributes
*/
static get observedAttributes(): string[];
private __instanceProperties?;
/**
* Creates a property accessor on the element prototype if one does not exist
* and stores a {@linkcode PropertyDeclaration} for the property with the
* given options. 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.
*
* This method may be overridden to customize properties; however,
* when doing so, it's important to call `super.createProperty` to ensure
* the property is setup correctly. This method calls
* `getPropertyDescriptor` internally to get a descriptor to install.
* To customize what properties do when they are get or set, override
* `getPropertyDescriptor`. To customize the options for a property,
* implement `createProperty` like this:
*
* ```ts
* static createProperty(name, options) {
* options = Object.assign(options, {myOption: true});
* super.createProperty(name, options);
* }
* ```
*
* @nocollapse
* @category properties
*/
static createProperty(name: PropertyKey, options?: PropertyDeclaration): void;
/**
* Returns a property descriptor to be defined on the given named property.
* If no descriptor is returned, the property will not become an accessor.
* For example,
*
* ```ts
* class MyElement extends LitElement {
* static getPropertyDescriptor(name, key, options) {
* const defaultDescriptor =
* super.getPropertyDescriptor(name, key, options);
* const setter = defaultDescriptor.set;
* return {
* get: defaultDescriptor.get,
* set(value) {
* setter.call(this, value);
* // custom action.
* },
* configurable: true,
* enumerable: true
* }
* }
* }
* ```
*
* @nocollapse
* @category properties
*/
protected static getPropertyDescriptor(name: PropertyKey, key: string | symbol, options: PropertyDeclaration): PropertyDescriptor | undefined;
/**
* Returns the property options associated with the given property.
* These options are defined with a `PropertyDeclaration` via the `properties`
* object or the `@property` decorator and are registered in
* `createProperty(...)`.
*
* Note, this method should be considered "final" and not overridden. To
* customize the options for a given property, override
* {@linkcode createProperty}.
*
* @nocollapse
* @final
* @category properties
*/
static getPropertyOptions(name: PropertyKey): PropertyDeclaration<unknown, unknown>;
static [Symbol.metadata]: object & Record<PropertyKey, unknown>;
/**
* Initializes static own properties of the class used in bookkeeping
* for element properties, initializers, etc.
*
* Can be called multiple times by code that needs to ensure these
* properties exist before using them.
*
* This method ensures the superclass is finalized so that inherited
* property metadata can be copied down.
* @nocollapse
*/
private static __prepare;
/**
* Finishes setting up the class so that it's ready to be registered
* as a custom element and instantiated.
*
* This method is called by the ReactiveElement.observedAttributes getter.
* If you override the observedAttributes getter, you must either call
* super.observedAttributes to trigger finalization, or call finalize()
* yourself.
*
* @nocollapse
*/
protected static finalize(): void;
/**
* Options used when calling `attachShadow`. Set this property to customize
* the options for the shadowRoot; for example, to create a closed
* shadowRoot: `{mode: 'closed'}`.
*
* Note, these options are used in `createRenderRoot`. If this method
* is customized, options should be respected if possible.
* @nocollapse
* @category rendering
*/
static shadowRootOptions: ShadowRootInit;
/**
* Takes the styles the user supplied via the `static styles` property and
* returns the array of styles to apply to the element.
* Override this method to integrate into a style management system.
*
* Styles are deduplicated preserving the _last_ instance in the list. This
* is a performance optimization to avoid duplicated styles that can occur
* especially when composing via subclassing. The last item is kept to try
* to preserve the cascade order with the assumption that it's most important
* that last added styles override previous styles.
*
* @nocollapse
* @category styles
*/
protected static finalizeStyles(styles?: CSSResultGroup): Array<CSSResultOrNative>;
/**
* Node or ShadowRoot into which element DOM should be rendered. Defaults
* to an open shadowRoot.
* @category rendering
*/
readonly renderRoot: HTMLElement | DocumentFragment;
/**
* Returns the property name for the given attribute `name`.
* @nocollapse
*/
private static __attributeNameForProperty;
private __updatePromise;
/**
* True if there is a pending update as a result of calling `requestUpdate()`.
* Should only be read.
* @category updates
*/
isUpdatePending: boolean;
/**
* Is set to `true` after the first update. The element code cannot assume
* that `renderRoot` exists before the element `hasUpdated`.
* @category updates
*/
hasUpdated: boolean;
/**
* Properties that should be reflected when updated.
*/
private __reflectingProperties?;
/**
* Name of currently reflecting property
*/
private __reflectingProperty;
/**
* Set of controllers.
*/
private __controllers?;
constructor();
/**
* Internal only override point for customizing work done when elements
* are constructed.
*/
private __initialize;
/**
* Registers a `ReactiveController` to participate in the element's reactive
* update cycle. The element automatically calls into any registered
* controllers during its lifecycle callbacks.
*
* If the element is connected when `addController()` is called, the
* controller's `hostConnected()` callback will be immediately called.
* @category controllers
*/
addController(controller: ReactiveController): void;
/**
* Removes a `ReactiveController` from the element.
* @category controllers
*/
removeController(controller: ReactiveController): void;
/**
* 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).
*/
private __saveInstanceProperties;
/**
* Returns the node into which the element should render and by default
* creates and returns an open shadowRoot. Implement to customize where the
* element's DOM is rendered. For example, to render into the element's
* childNodes, return `this`.
*
* @return Returns a node into which to render.
* @category rendering
*/
protected createRenderRoot(): HTMLElement | DocumentFragment;
/**
* On first connection, creates the element's renderRoot, sets up
* element styling, and enables updating.
* @category lifecycle
*/
connectedCallback(): void;
/**
* Note, this method should be considered final and not overridden. It is
* overridden on the element instance with a function that triggers the first
* update.
* @category updates
*/
protected enableUpdating(_requestedUpdate: boolean): void;
/**
* Allows for `super.disconnectedCallback()` in extensions while
* reserving the possibility of making non-breaking feature additions
* when disconnecting at some point in the future.
* @category lifecycle
*/
disconnectedCallback(): void;
/**
* Synchronizes property values when attributes change.
*
* Specifically, when an attribute is set, the corresponding property is set.
* You should rarely need to implement this callback. If this method is
* overridden, `super.attributeChangedCallback(name, _old, value)` must be
* called.
*
* See [using the lifecycle callbacks](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_custom_elements#using_the_lifecycle_callbacks)
* on MDN for more information about the `attributeChangedCallback`.
* @category attributes
*/
attributeChangedCallback(name: string, _old: string | null, value: string | null): void;
private __propertyToAttribute;
/**
* 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 reactive 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.
*
* @param name name of requesting property
* @param oldValue old value of requesting property
* @param options property options to use instead of the previously
* configured options
* @param initial whether this call is for the initial value of the property.
* Initial values do not reflect to an attribute.
* @category updates
*/
requestUpdate(name?: PropertyKey, oldValue?: unknown, options?: PropertyDeclaration): void;
/**
* Sets up the element to asynchronously update.
*/
private __enqueueUpdate;
/**
* Schedules an element update. You can override this method to change the
* timing of updates by returning a Promise. The update will await the
* returned Promise, and you should resolve the Promise to allow the update
* to proceed. If this method is overridden, `super.scheduleUpdate()`
* must be called.
*
* For instance, to schedule updates to occur just before the next frame:
*
* ```ts
* override protected async scheduleUpdate(): Promise<unknown> {
* await new Promise((resolve) => requestAnimationFrame(() => resolve()));
* super.scheduleUpdate();
* }
* ```
* @category updates
*/
protected scheduleUpdate(): void | Promise<unknown>;
/**
* Performs an element update. Note, if an exception is thrown during the
* update, `firstUpdated` and `updated` will not be called.
*
* Call `performUpdate()` to immediately process a pending update. This should
* generally not be needed, but it can be done in rare cases when you need to
* update synchronously.
*
* @category updates
*/
protected performUpdate(): void;
/**
* Invoked before `update()` to compute values needed during the update.
*
* Implement `willUpdate` to compute property values that depend on other
* properties and are used in the rest of the update process.
*
* ```ts
* willUpdate(changedProperties) {
* // only need to check changed properties for an expensive computation.
* if (changedProperties.has('firstName') || changedProperties.has('lastName')) {
* this.sha = computeSHA(`${this.firstName} ${this.lastName}`);
* }
* }
*
* render() {
* return html`SHA: ${this.sha}`;
* }
* ```
*
* @category updates
*/
protected willUpdate(_changedProperties: PropertyValues): void;
private __markUpdated;
/**
* 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()`. If the Promise is rejected, an
* exception was thrown during the update.
*
* To await additional asynchronous work, override the `getUpdateComplete`
* method. For example, it is sometimes useful to await a rendered element
* before fulfilling this Promise. To do this, first await
* `super.getUpdateComplete()`, then any subsequent state.
*
* @return A promise of a boolean that resolves to true if the update completed
* without triggering another update.
* @category updates
*/
get updateComplete(): Promise<boolean>;
/**
* Override point for the `updateComplete` promise.
*
* It is not safe to override the `updateComplete` getter directly due to a
* limitation in TypeScript which means it is not possible to call a
* superclass getter (e.g. `super.updateComplete.then(...)`) when the target
* language is ES5 (https://github.com/microsoft/TypeScript/issues/338).
* This method should be overridden instead. For example:
*
* ```ts
* class MyElement extends LitElement {
* override async getUpdateComplete() {
* const result = await super.getUpdateComplete();
* await this._myChild.updateComplete;
* return result;
* }
* }
* ```
*
* @return A promise of a boolean that resolves to true if the update completed
* without triggering another update.
* @category updates
*/
protected getUpdateComplete(): Promise<boolean>;
/**
* 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
* @category updates
*/
protected shouldUpdate(_changedProperties: PropertyValues): boolean;
/**
* 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
* @category updates
*/
protected update(_changedProperties: PropertyValues): void;
/**
* 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
* @category updates
*/
protected updated(_changedProperties: PropertyValues): void;
/**
* Invoked when the element is first updated. Implement to perform one time
* work on the element after update.
*
* ```ts
* firstUpdated() {
* this.renderRoot.getElementById('my-text-area').focus();
* }
* ```
*
* 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
* @category updates
*/
protected firstUpdated(_changedProperties: PropertyValues): void;
}
//# sourceMappingURL=reactive-element.d.ts.map
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