=\n (globalThis.litIssuedWarnings ??= new Set());\n\n // Issue a warning, if we haven't already.\n issueWarning = (code: string, warning: string) => {\n warning += ` See https://lit.dev/msg/${code} for more information.`;\n if (!issuedWarnings.has(warning)) {\n console.warn(warning);\n issuedWarnings.add(warning);\n }\n };\n\n issueWarning(\n 'dev-mode',\n `Lit is in dev mode. Not recommended for production!`\n );\n\n // Issue polyfill support warning.\n if (window.ShadyDOM?.inUse && polyfillSupport === undefined) {\n issueWarning(\n 'polyfill-support-missing',\n `Shadow DOM is being polyfilled via \\`ShadyDOM\\` but ` +\n `the \\`polyfill-support\\` module has not been loaded.`\n );\n }\n\n requestUpdateThenable = (name) => ({\n then: (\n onfulfilled?: (value: boolean) => void,\n _onrejected?: () => void\n ) => {\n issueWarning(\n 'request-update-promise',\n `The \\`requestUpdate\\` method should no longer return a Promise but ` +\n `does so on \\`${name}\\`. Use \\`updateComplete\\` instead.`\n );\n if (onfulfilled !== undefined) {\n onfulfilled(false);\n }\n },\n });\n}\n\n/*\n * When using Closure Compiler, JSCompiler_renameProperty(property, object) is\n * replaced at compile time by the munged name for object[property]. We cannot\n * alias this function, so we have to use a small shim that has the same\n * behavior when not compiling.\n */\n/*@__INLINE__*/\nconst JSCompiler_renameProperty = (\n prop: P,\n _obj: unknown\n): P => prop;\n\n/**\n * Converts property values to and from attribute values.\n */\nexport interface ComplexAttributeConverter {\n /**\n * Called to convert an attribute value to a property\n * value.\n */\n fromAttribute?(value: string | null, type?: TypeHint): Type;\n\n /**\n * Called to convert a property value to an attribute\n * value.\n *\n * It returns unknown instead of string, to be compatible with\n * https://github.com/WICG/trusted-types (and similar efforts).\n */\n toAttribute?(value: Type, type?: TypeHint): unknown;\n}\n\ntype AttributeConverter =\n | ComplexAttributeConverter\n | ((value: string | null, type?: TypeHint) => Type);\n\n/**\n * Defines options for a property accessor.\n */\nexport interface PropertyDeclaration {\n /**\n * When set to `true`, indicates the property is internal private state. The\n * property should not be set by users. When using TypeScript, this property\n * should be marked as `private` or `protected`, and it is also a common\n * practice to use a leading `_` in the name. The property is not added to\n * `observedAttributes`.\n */\n readonly state?: boolean;\n\n /**\n * Indicates how and whether the property becomes an observed attribute.\n * If the value is `false`, the property is not added to `observedAttributes`.\n * If true or absent, the lowercased property name is observed (e.g. `fooBar`\n * becomes `foobar`). If a string, the string value is observed (e.g\n * `attribute: 'foo-bar'`).\n */\n readonly attribute?: boolean | string;\n\n /**\n * Indicates the type of the property. This is used only as a hint for the\n * `converter` to determine how to convert the attribute\n * to/from a property.\n */\n readonly type?: TypeHint;\n\n /**\n * Indicates how to convert the attribute to/from a property. If this value\n * is a function, it is used to convert the attribute value a the property\n * value. If it's an object, it can have keys for `fromAttribute` and\n * `toAttribute`. If no `toAttribute` function is provided and\n * `reflect` is set to `true`, the property value is set directly to the\n * attribute. A default `converter` is used if none is provided; it supports\n * `Boolean`, `String`, `Number`, `Object`, and `Array`. Note,\n * when a property changes and the converter is used to update the attribute,\n * the property is never updated again as a result of the attribute changing,\n * and vice versa.\n */\n readonly converter?: AttributeConverter;\n\n /**\n * Indicates if the property should reflect to an attribute.\n * If `true`, when the property is set, the attribute is set using the\n * attribute name determined according to the rules for the `attribute`\n * property option and the value of the property converted using the rules\n * from the `converter` property option.\n */\n readonly reflect?: boolean;\n\n /**\n * A function that indicates if a property should be considered changed when\n * it is set. The function should take the `newValue` and `oldValue` and\n * return `true` if an update should be requested.\n */\n hasChanged?(value: Type, oldValue: Type): boolean;\n\n /**\n * Indicates whether an accessor will be created for this property. By\n * default, an accessor will be generated for this property that requests an\n * update when set. If this flag is `true`, no accessor will be created, and\n * it will be the user's responsibility to call\n * `this.requestUpdate(propertyName, oldValue)` to request an update when\n * the property changes.\n */\n readonly noAccessor?: boolean;\n}\n\n/**\n * Map of properties to PropertyDeclaration options. For each property an\n * accessor is made, and the property is processed according to the\n * PropertyDeclaration options.\n */\nexport interface PropertyDeclarations {\n readonly [key: string]: PropertyDeclaration;\n}\n\ntype PropertyDeclarationMap = Map;\n\ntype AttributeMap = Map;\n\n/**\n * Map of changed properties with old values. Takes an optional generic\n * interface corresponding to the declared element properties.\n */\n// eslint-disable-next-line @typescript-eslint/no-explicit-any\nexport type PropertyValues = keyof T extends PropertyKey\n ? Map\n : never;\n\nexport const defaultConverter: ComplexAttributeConverter = {\n toAttribute(value: unknown, type?: unknown): unknown {\n switch (type) {\n case Boolean:\n value = value ? '' : null;\n break;\n case Object:\n case Array:\n // if the value is `null` or `undefined` pass this through\n // to allow removing/no change behavior.\n value = value == null ? value : JSON.stringify(value);\n break;\n }\n return value;\n },\n\n fromAttribute(value: string | null, type?: unknown) {\n let fromValue: unknown = value;\n switch (type) {\n case Boolean:\n fromValue = value !== null;\n break;\n case Number:\n fromValue = value === null ? null : Number(value);\n break;\n case Object:\n case Array:\n // Do *not* generate exception when invalid JSON is set as elements\n // don't normally complain on being mis-configured.\n // TODO(sorvell): Do generate exception in *dev mode*.\n try {\n // Assert to adhere to Bazel's \"must type assert JSON parse\" rule.\n fromValue = JSON.parse(value!) as unknown;\n } catch (e) {\n fromValue = null;\n }\n break;\n }\n return fromValue;\n },\n};\n\nexport interface HasChanged {\n (value: unknown, old: unknown): boolean;\n}\n\n/**\n * Change function that returns true if `value` is different from `oldValue`.\n * This method is used as the default for a property's `hasChanged` function.\n */\nexport const notEqual: HasChanged = (value: unknown, old: unknown): boolean => {\n // This ensures (old==NaN, value==NaN) always returns false\n return old !== value && (old === old || value === value);\n};\n\nconst defaultPropertyDeclaration: PropertyDeclaration = {\n attribute: true,\n type: String,\n converter: defaultConverter,\n reflect: false,\n hasChanged: notEqual,\n};\n\n/**\n * The Closure JS Compiler doesn't currently have good support for static\n * property semantics where \"this\" is dynamic (e.g.\n * https://github.com/google/closure-compiler/issues/3177 and others) so we use\n * this hack to bypass any rewriting by the compiler.\n */\nconst finalized = 'finalized';\n\n/**\n * A string representing one of the supported dev mode warning categories.\n */\nexport type WarningKind = 'change-in-update' | 'migration';\n\nexport type Initializer = (element: ReactiveElement) => void;\n\n/**\n * Base element class which manages element properties and attributes. When\n * properties change, the `update` method is asynchronously called. This method\n * should be supplied by subclassers to render updates as desired.\n * @noInheritDoc\n */\nexport abstract class ReactiveElement\n extends HTMLElement\n implements ReactiveControllerHost\n{\n // Note: these are patched in only in DEV_MODE.\n /**\n * Read or set all the enabled warning categories for this class.\n *\n * This property is only used in development builds.\n *\n * @nocollapse\n * @category dev-mode\n */\n static enabledWarnings?: WarningKind[];\n\n /**\n * Enable the given warning category for this class.\n *\n * This method only exists in development builds, so it should be accessed\n * with a guard like:\n *\n * ```ts\n * // Enable for all ReactiveElement subclasses\n * ReactiveElement.enableWarning.?('migration');\n *\n * // Enable for only MyElement and subclasses\n * MyElement.enableWarning.?('migration');\n * ```\n *\n * @nocollapse\n * @category dev-mode\n */\n static enableWarning?: (warningKind: WarningKind) => void;\n\n /**\n * Disable the given warning category for this class.\n *\n * This method only exists in development builds, so it should be accessed\n * with a guard like:\n *\n * ```ts\n * // Disable for all ReactiveElement subclasses\n * ReactiveElement.disableWarning.?('migration');\n *\n * // Disable for only MyElement and subclasses\n * MyElement.disableWarning.?('migration');\n * ```\n *\n * @nocollapse\n * @category dev-mode\n */\n static disableWarning?: (warningKind: WarningKind) => void;\n\n /**\n * Adds an initializer function to the class that is called during instance\n * construction.\n *\n * This is useful for code that runs against a `ReactiveElement`\n * subclass, such as a decorator, that needs to do work for each\n * instance, such as setting up a `ReactiveController`.\n *\n * ```ts\n * const myDecorator = (target: typeof ReactiveElement, key: string) => {\n * target.addInitializer((instance: ReactiveElement) => {\n * // This is run during construction of the element\n * new MyController(instance);\n * });\n * }\n * ```\n *\n * Decorating a field will then cause each instance to run an initializer\n * that adds a controller:\n *\n * ```ts\n * class MyElement extends LitElement {\n * @myDecorator foo;\n * }\n * ```\n *\n * Initializers are stored per-constructor. Adding an initializer to a\n * subclass does not add it to a superclass. Since initializers are run in\n * constructors, initializers will run in order of the class hierarchy,\n * starting with superclasses and progressing to the instance's class.\n *\n * @nocollapse\n */\n static addInitializer(initializer: Initializer) {\n this._initializers ??= [];\n this._initializers.push(initializer);\n }\n\n static _initializers?: Initializer[];\n\n /*\n * Due to closure compiler ES6 compilation bugs, @nocollapse is required on\n * all static methods and properties with initializers. Reference:\n * - https://github.com/google/closure-compiler/issues/1776\n */\n\n /**\n * Maps attribute names to properties; for example `foobar` attribute to\n * `fooBar` property. Created lazily on user subclasses when finalizing the\n * class.\n * @nocollapse\n */\n private static __attributeToPropertyMap: AttributeMap;\n\n /**\n * Marks class as having finished creating properties.\n */\n protected static [finalized] = true;\n\n /**\n * Memoized list of all element properties, including any superclass properties.\n * Created lazily on user subclasses when finalizing the class.\n * @nocollapse\n * @category properties\n */\n static elementProperties: PropertyDeclarationMap = new Map();\n\n /**\n * User-supplied object that maps property names to `PropertyDeclaration`\n * objects containing options for configuring reactive properties. When\n * a reactive property is set the element will update and render.\n *\n * By default properties are public fields, and as such, they should be\n * considered as primarily settable by element users, either via attribute or\n * the property itself.\n *\n * Generally, properties that are changed by the element should be private or\n * protected fields and should use the `state: true` option. Properties\n * marked as `state` do not reflect from the corresponding attribute\n *\n * However, sometimes element code does need to set a public property. This\n * should typically only be done in response to user interaction, and an event\n * should be fired informing the user; for example, a checkbox sets its\n * `checked` property when clicked and fires a `changed` event. Mutating\n * public properties should typically not be done for non-primitive (object or\n * array) properties. In other cases when an element needs to manage state, a\n * private property set with the `state: true` option should be used. When\n * needed, state properties can be initialized via public properties to\n * facilitate complex interactions.\n * @nocollapse\n * @category properties\n */\n static properties: PropertyDeclarations;\n\n /**\n * Memoized list of all element styles.\n * Created lazily on user subclasses when finalizing the class.\n * @nocollapse\n * @category styles\n */\n static elementStyles: Array = [];\n\n /**\n * Array of styles to apply to the element. The styles should be defined\n * using the [[`css`]] tag function, via constructible stylesheets, or\n * imported from native CSS module scripts.\n *\n * Note on Content Security Policy:\n *\n * Element styles are implemented with `