Render should always return a html template (#4612)

cast/src/launcher/layout/hc-cast.ts

@@ -39,7 +39,7 @@ class HcCast extends LitElement {
   @property() private askWrite = false;
   @property() private lovelaceConfig?: LovelaceConfig | null;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (this.lovelaceConfig === undefined) {
       return html`
         <loading-screen></loading-screen>>

cast/src/launcher/layout/hc-connect.ts

@@ -70,7 +70,7 @@ export class HcConnect extends LitElement {
   @property() private castManager?: CastManager | null;
   private openDemo = false;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (this.cannotConnect) {
       const tokens = loadTokens();
       return html`

cast/src/launcher/layout/hc-layout.ts

@@ -22,7 +22,7 @@ class HcLayout extends LitElement {
   @property() public connection?: Connection;
   @property() public user?: HassUser;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <ha-card>
         <div class="layout">

cast/src/receiver/layout/hc-demo.ts

@@ -16,7 +16,7 @@ class HcDemo extends HassElement {
   @property() public lovelacePath!: string;
   @property() private _lovelaceConfig?: LovelaceConfig;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._lovelaceConfig) {
       return html``;
     }

cast/src/receiver/layout/hc-launch-screen.ts

@@ -14,7 +14,7 @@ class HcLaunchScreen extends LitElement {
   @property() public hass?: HomeAssistant;
   @property() public error?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="container">
         <img

cast/src/receiver/layout/hc-lovelace.ts

@@ -22,7 +22,7 @@ class HcLovelace extends LitElement {
 
   @property() public viewPath?: string | number;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const index = this._viewIndex;
     if (index === undefined) {
       return html`

cast/src/receiver/layout/hc-main.ts

@@ -50,7 +50,7 @@ export class HcMain extends HassElement {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (this._showDemo) {
       return html`
         <hc-demo .lovelacePath=${this._lovelacePath}></hc-demo>

demo/src/custom-cards/cast-demo-row.ts

@@ -27,7 +27,7 @@ class CastDemoRow extends LitElement implements LovelaceRow {
     // No config possible.
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (
       !this._castManager ||
       this._castManager.castState === "NO_DEVICES_AVAILABLE"

gallery/src/demos/demo-util-long-press.ts

@@ -6,7 +6,7 @@ import { actionHandler } from "../../../src/panels/lovelace/common/directives/ac
 import { ActionHandlerEvent } from "../../../src/data/lovelace";
 
 export class DemoUtilLongPress extends LitElement {
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       ${this.renderStyle()}
       ${[1, 2, 3].map(

hassio/src/addon-store/hassio-addon-repository.ts

@@ -36,7 +36,7 @@ class HassioAddonRepositoryEl extends LitElement {
     }
   );
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const repo = this.repo;
     const addons = this._getAddons(this.addons, this.filter);
 

hassio/src/addon-store/hassio-addon-store.ts

@@ -48,7 +48,7 @@ class HassioAddonStore extends LitElement {
     await this._loadData();
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._addons || !this._repos) {
       return html`
         <loading-screen></loading-screen>

hassio/src/addon-store/hassio-repositories-editor.ts

@@ -33,7 +33,7 @@ class HassioRepositoriesEditor extends LitElement {
       .sort((a, b) => (a.name < b.name ? -1 : 1))
   );
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const repos = this._sortedRepos(this.repos);
     return html`
       <div class="card-group">

hassio/src/addon-view/hassio-addon-audio.ts

@@ -39,7 +39,7 @@ class HassioAddonAudio extends LitElement {
   @property() private _selectedInput!: null | string;
   @property() private _selectedOutput!: null | string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <paper-card heading="Audio">
         <div class="card-content">

hassio/src/addon-view/hassio-addon-config.ts

@@ -31,7 +31,7 @@ class HassioAddonConfig extends LitElement {
   @property() private _config!: string;
   @property({ type: Boolean }) private _configHasChanged = false;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <paper-card heading="Config">
         <div class="card-content">

hassio/src/addon-view/hassio-addon-info.ts

@@ -95,7 +95,7 @@ class HassioAddonInfo extends LitElement {
   @property() public addon!: HassioAddonDetails;
   @property() private _error?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       ${
         this._computeUpdateAvailable

hassio/src/addon-view/hassio-addon-logs.ts

@@ -31,7 +31,7 @@ class HassioAddonLogs extends LitElement {
     await this._loadData();
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <paper-card heading="Log">
         ${this._error

hassio/src/addon-view/hassio-addon-network.ts

@@ -44,7 +44,7 @@ class HassioAddonNetwork extends LitElement {
     this._setNetworkConfig();
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._config) {
       return html``;
     }

hassio/src/addon-view/hassio-addon-view.ts

@@ -33,7 +33,7 @@ class HassioAddonView extends LitElement {
   @property() public route!: Route;
   @property() public addon?: HassioAddonDetails;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.addon) {
       return html`
         <paper-spinner-lite active></paper-spinner-lite>

hassio/src/components/hassio-card-content.ts

@@ -23,7 +23,7 @@ class HassioCardContent extends LitElement {
   @property() public iconClass?: string;
   @property() public icon = "hass:help-circle";
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <iron-icon
         class=${this.iconClass}

hassio/src/components/hassio-search-input.ts

@@ -16,7 +16,7 @@ import "@material/mwc-button";
 class HassioSearchInput extends LitElement {
   @property() private filter?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="search-container">
         <paper-input

hassio/src/dashboard/hassio-addons.ts

@@ -21,7 +21,7 @@ class HassioAddons extends LitElement {
   @property() public hass!: HomeAssistant;
   @property() public addons?: HassioAddonInfo[];
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="content card-group">
         <div class="title">Add-ons</div>

hassio/src/dashboard/hassio-dashboard.ts

@@ -24,7 +24,7 @@ class HassioDashboard extends LitElement {
   @property() public hassInfo!: HassioHomeAssistantInfo;
   @property() public hassOsInfo!: HassioHassOSInfo;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="content">
         <hassio-update

hassio/src/dashboard/hassio-update.ts

@@ -32,7 +32,7 @@ export class HassioUpdate extends LitElement {
   @property() public supervisorInfo: HassioSupervisorInfo;
   @property() private _error?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const updatesAvailable: number = [
       this.hassInfo,
       this.supervisorInfo,

hassio/src/dialogs/markdown/dialog-hassio-markdown.ts

@@ -32,7 +32,7 @@ class HassioMarkdownDialog extends LitElement {
     this._dialog.open();
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <ha-paper-dialog id="dialog" with-backdrop="">
         <app-toolbar>

hassio/src/dialogs/snapshot/dialog-hassio-snapshot.ts

@@ -102,7 +102,7 @@ class HassioSnapshotDialog extends LitElement {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.snapshot) {
       return html``;
     }

hassio/src/hassio-pages-with-tabs.ts

@@ -41,7 +41,7 @@ class HassioPagesWithTabs extends LitElement {
   @property() public hassInfo!: HassioHomeAssistantInfo;
   @property() public hassOsInfo!: HassioHassOSInfo;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const page = this._page;
     return html`
       <app-header-layout has-scrolling-region>

hassio/src/ingress-view/hassio-ingress-view.ts

@@ -23,7 +23,7 @@ class HassioIngressView extends LitElement {
   @property() public route!: Route;
   @property() private _addon?: HassioAddonDetails;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._addon) {
       return html`
         <hass-loading-screen></hass-loading-screen>

hassio/src/snapshots/hassio-snapshots.ts

@@ -76,7 +76,7 @@ class HassioSnapshots extends LitElement {
     await this._updateSnapshots();
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="content">
         <div class="card-group">

src/cards/ha-badges-card.ts

@@ -12,7 +12,7 @@ class HaBadgesCard extends LitElement {
   @property() public hass?: HomeAssistant;
   @property() public states?: HassEntity[];
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.states) {
       return html``;
     }

src/common/search/search-input.ts

@@ -20,7 +20,7 @@ class SearchInput extends LitElement {
     this.shadowRoot!.querySelector("paper-input")!.focus();
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="search-container">
         <paper-input

src/components/device/ha-area-devices-picker.ts

@@ -255,9 +255,9 @@ export class HaAreaDevicesPicker extends SubscribeMixin(LitElement) {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._devices || !this._areas || !this._entities) {
-      return;
+      return html``;
     }
     const areas = this._getDevices(
       this._devices,

src/components/device/ha-device-automation-picker.ts

@@ -83,7 +83,7 @@ export abstract class HaDeviceAutomationPicker<
     return `${this._automations[idx].device_id}_${idx}`;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (this._renderEmpty) {
       return html``;
     }

src/components/device/ha-device-picker.ts

@@ -203,9 +203,9 @@ export class HaDevicePicker extends SubscribeMixin(LitElement) {
     ];
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.devices || !this.areas || !this.entities) {
-      return;
+      return html``;
     }
     const devices = this._getDevices(
       this.devices,

src/components/device/ha-devices-picker.ts

@@ -37,9 +37,9 @@ class HaDevicesPicker extends LitElement {
   public pickedDeviceLabel?: string;
   @property({ attribute: "pick-device-label" }) public pickDeviceLabel?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass) {
-      return;
+      return html``;
     }
 
     const currentDevices = this._currentDevices;

src/components/entity/ha-entities-picker.ts

@@ -40,9 +40,9 @@ class HaEntitiesPickerLight extends LitElement {
   public pickedEntityLabel?: string;
   @property({ attribute: "pick-entity-label" }) public pickEntityLabel?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass) {
-      return;
+      return html``;
     }
 
     const currentEntities = this._currentEntities;

src/components/entity/ha-entity-picker.ts

@@ -145,7 +145,7 @@ class HaEntityPicker extends LitElement {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const states = this._getStates(
       this._hass,
       this.includeDomains,

src/components/entity/ha-entity-toggle.ts

@@ -28,7 +28,7 @@ class HaEntityToggle extends LitElement {
   @property() public stateObj?: HassEntity;
   @property() private _isOn: boolean = false;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.stateObj) {
       return html`
         <ha-switch disabled></ha-switch>

src/components/entity/ha-state-label-badge.ts

@@ -52,7 +52,7 @@ export class HaStateLabelBadge extends LitElement {
     this.clearInterval();
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const state = this.state;
 
     if (!state) {

src/components/entity/state-badge.ts

@@ -28,7 +28,7 @@ export class StateBadge extends LitElement {
   @property({ type: Boolean }) public stateColor?: boolean;
   @query("ha-icon") private _icon!: HaIcon;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const stateObj = this.stateObj;
 
     if (!stateObj) {

src/components/ha-area-picker.ts

@@ -85,9 +85,9 @@ export class HaAreaPicker extends SubscribeMixin(LitElement) {
     ];
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._areas) {
-      return;
+      return html``;
     }
     return html`
       <vaadin-combo-box-light

src/components/ha-attributes.ts

@@ -16,7 +16,7 @@ class HaAttributes extends LitElement {
   @property() public stateObj?: HassEntity;
   @property() public extraFilters?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.stateObj) {
       return html``;
     }

src/components/ha-camera-stream.ts

@@ -42,7 +42,7 @@ class HaCameraStream extends LitElement {
     this._attached = false;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.stateObj || !this._attached) {
       return html``;
     }

src/components/ha-form/ha-form-positive_time_period_dict.ts

@@ -23,7 +23,7 @@ export class HaFormTimePeriod extends LitElement implements HaFormElement {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <paper-time-input
         .label=${this.label}

src/components/ha-label-badge.ts

@@ -17,7 +17,7 @@ class HaLabelBadge extends LitElement {
   @property() public description?: string;
   @property() public image?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="badge-container">
         <div class="label-badge" id="badge">

src/components/ha-menu-button.ts

@@ -42,7 +42,7 @@ class HaMenuButton extends LitElement {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const hasNotifications =
       (this.narrow || this.hass.dockedSidebar === "always_hidden") &&
       (this._hasNotifications ||

src/components/ha-related-items.ts

@@ -64,7 +64,7 @@ export class HaRelatedItems extends SubscribeMixin(LitElement) {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._related) {
       return html``;
     }

src/components/map/ha-location-editor.ts

@@ -50,7 +50,7 @@ class LocationEditor extends LitElement {
     this._ignoreFitToMap = this.location;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div id="map"></div>
     `;

src/components/map/ha-locations-editor.ts

@@ -90,7 +90,7 @@ export class HaLocationsEditor extends LitElement {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div id="map"></div>
     `;

src/components/user/ha-user-badge.ts

@@ -31,7 +31,7 @@ const computeInitials = (name: string) => {
 class StateBadge extends LitElement {
   @property() public user?: User | CurrentUser;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const user = this.user;
     const initials = user ? computeInitials(user.name) : "?";
     return html`

src/components/user/ha-user-picker.ts

@@ -34,7 +34,7 @@ class HaUserPicker extends LitElement {
       .sort((a, b) => compare(a.name, b.name));
   });
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <paper-dropdown-menu-light .label=${this.label}>
         <paper-listbox

src/dialogs/config-entry-system-options/dialog-config-entry-system-options.ts

@@ -48,7 +48,7 @@ class DialogConfigEntrySystemOptions extends LitElement {
     await this.updateComplete;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._params) {
       return html``;
     }

src/dialogs/config-flow/dialog-data-entry-flow.ts

@@ -116,7 +116,7 @@ class DataEntryFlowDialog extends LitElement {
     this._scheduleCenterDialog();
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._params) {
       return html``;
     }

src/dialogs/config-flow/step-flow-abort.ts

@@ -24,7 +24,7 @@ class StepFlowAbort extends LitElement {
   @property()
   private step!: DataEntryFlowStepAbort;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <h2>
         ${this.hass.localize(

src/dialogs/config-flow/step-flow-create-entry.ts

@@ -36,7 +36,7 @@ class StepFlowCreateEntry extends LitElement {
   @property()
   public devices!: DeviceRegistryEntry[];
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const localize = this.hass.localize;
 
     return html`

src/dialogs/config-flow/step-flow-external.ts

@@ -28,7 +28,7 @@ class StepFlowExternal extends LitElement {
   @property()
   private step!: DataEntryFlowStepExternal;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const localize = this.hass.localize;
 
     return html`

src/dialogs/config-flow/step-flow-form.ts

@@ -40,7 +40,7 @@ class StepFlowForm extends LitElement {
   @property()
   private _errorMsg?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const step = this.step;
     const stepData = this._stepDataProcessed;
 

src/dialogs/config-flow/step-flow-loading.ts

@@ -10,7 +10,7 @@ import "@polymer/paper-spinner/paper-spinner-lite";
 
 @customElement("step-flow-loading")
 class StepFlowLoading extends LitElement {
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="init-spinner">
         <paper-spinner-lite active></paper-spinner-lite>

src/dialogs/config-flow/step-flow-pick-handler.ts

@@ -59,7 +59,7 @@ class StepFlowPickHandler extends LitElement {
     );
   });
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const handlers = this._getHandlers(this.handlers, this.filter);
 
     return html`

src/dialogs/device-registry-detail/dialog-device-registry-detail.ts

@@ -44,7 +44,7 @@ class DialogDeviceRegistryDetail extends LitElement {
     await this.updateComplete;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._params) {
       return html``;
     }

src/dialogs/domain-toggler/dialog-domain-toggler.ts

@@ -22,7 +22,7 @@ class DomainTogglerDialog extends LitElement {
     this._params = params;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._params) {
       return html``;
     }

src/dialogs/generic/dialog-box.ts

@@ -32,7 +32,7 @@ class DialogBox extends LitElement {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._params) {
       return html``;
     }

src/dialogs/more-info/controls/more-info-automation.ts

@@ -19,7 +19,7 @@ class MoreInfoAutomation extends LitElement {
   @property() public hass!: HomeAssistant;
   @property() public stateObj?: HassEntity;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.stateObj) {
       return html``;
     }

src/dialogs/more-info/controls/more-info-camera.ts

@@ -38,7 +38,7 @@ class MoreInfoCamera extends LitElement {
     this._attached = false;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._attached || !this.hass || !this.stateObj) {
       return html``;
     }

src/dialogs/more-info/controls/more-info-climate.ts

@@ -39,7 +39,7 @@ class MoreInfoClimate extends LitElement {
   @property() public stateObj?: ClimateEntity;
   private _resizeDebounce?: number;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.stateObj) {
       return html``;
     }

src/dialogs/more-info/controls/more-info-counter.ts

@@ -17,7 +17,7 @@ class MoreInfoCounter extends LitElement {
   @property() public hass!: HomeAssistant;
   @property() public stateObj?: HassEntity;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.stateObj) {
       return html``;
     }

src/dialogs/more-info/controls/more-info-default.ts

@@ -16,7 +16,7 @@ class MoreInfoDefault extends LitElement {
   @property() public hass!: HomeAssistant;
   @property() public stateObj?: HassEntity;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.stateObj) {
       return html``;
     }

src/dialogs/more-info/controls/more-info-script.ts

@@ -16,7 +16,7 @@ class MoreInfoScript extends LitElement {
   @property() public hass!: HomeAssistant;
   @property() public stateObj?: HassEntity;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.stateObj) {
       return html``;
     }

src/dialogs/more-info/controls/more-info-sun.ts

@@ -19,7 +19,7 @@ class MoreInfoSun extends LitElement {
   @property() public hass!: HomeAssistant;
   @property() public stateObj?: HassEntity;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.stateObj) {
       return html``;
     }

src/dialogs/more-info/controls/more-info-timer.ts

@@ -19,7 +19,7 @@ class MoreInfoTimer extends LitElement {
 
   @property() public stateObj?: TimerEntity;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.stateObj) {
       return html``;
     }

src/dialogs/more-info/controls/more-info-weather.ts

@@ -72,7 +72,7 @@ class MoreInfoWeather extends LitElement {
     return false;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.stateObj) {
       return html``;
     }

src/dialogs/notifications/configurator-notification-item.ts

@@ -19,7 +19,7 @@ export class HuiConfiguratorNotificationItem extends LitElement {
 
   @property() public notification?: PersitentNotificationEntity;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.notification) {
       return html``;
     }

src/dialogs/notifications/notification-item-template.ts

@@ -11,7 +11,7 @@ import "../../components/ha-card";
 
 @customElement("notification-item-template")
 export class HuiNotificationItemTemplate extends LitElement {
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <ha-card>
         <div class="header"><slot name="header"></slot></div>

src/dialogs/notifications/notification-item.ts

@@ -28,7 +28,7 @@ export class HuiNotificationItem extends LitElement {
     return false;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.notification) {
       return html``;
     }

src/dialogs/notifications/persistent-notification-item.ts

@@ -23,7 +23,7 @@ export class HuiPersistentNotificationItem extends LitElement {
 
   @property() public notification?: PersistentNotification;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || !this.notification) {
       return html``;
     }

src/dialogs/zha-device-info-dialog/dialog-zha-device-info.ts

@@ -34,7 +34,7 @@ class DialogZHADeviceInfo extends LitElement {
     this._dialog.open();
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._params || !this._device) {
       return html``;
     }

src/layouts/hass-error-screen.ts

@@ -15,7 +15,7 @@ class HassErrorScreen extends LitElement {
   @property()
   public error?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <hass-subpage>
         <div class="content">

src/layouts/hass-loading-screen.ts

@@ -20,7 +20,7 @@ class HassLoadingScreen extends LitElement {
   @property() public hass?: HomeAssistant;
   @property() public narrow?: boolean;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <app-toolbar>
         ${this.rootnav

src/layouts/hass-subpage.ts

@@ -20,7 +20,7 @@ class HassSubpage extends LitElement {
   @property({ type: Boolean })
   public hassio = false;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="toolbar">
         <ha-paper-icon-button-arrow-prev

src/layouts/home-assistant-main.ts

@@ -38,11 +38,11 @@ class HomeAssistantMain extends LitElement {
   @property() public route?: Route;
   @property({ type: Boolean }) private narrow?: boolean;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const hass = this.hass;
 
     if (!hass) {
-      return;
+      return html``;
     }
 
     const sidebarNarrow = this._sidebarNarrow;

src/layouts/loading-screen.ts

@@ -10,7 +10,7 @@ import {
 
 @customElement("loading-screen")
 class LoadingScreen extends LitElement {
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <paper-spinner-lite active></paper-spinner-lite>
     `;

src/managers/notification-manager.ts

@@ -58,7 +58,7 @@ class NotificationManager extends LitElement {
     });
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <ha-toast .noCancelOnOutsideClick=${this._noCancelOnOutsideClick}>
         ${this._action

src/onboarding/ha-onboarding.ts

@@ -50,7 +50,7 @@ class HaOnboarding extends litLocalizeLiteMixin(HassElement) {
   @property() private _loading = false;
   @property() private _steps?: OnboardingStep[];
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const step = this._curStep()!;
 
     if (this._loading || !step) {
@@ -79,6 +79,7 @@ class HaOnboarding extends litLocalizeLiteMixin(HassElement) {
         ></onboarding-integrations>
       `;
     }
+    return html``;
   }
 
   protected firstUpdated(changedProps: PropertyValues) {

src/onboarding/integration-badge.ts

@@ -16,7 +16,7 @@ class IntegrationBadge extends LitElement {
   @property() public badgeIcon?: string;
   @property({ type: Boolean, reflect: true }) public clickable = false;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="icon">
         <iron-icon .icon=${this.icon}></iron-icon>

src/onboarding/onboarding-core-config.ts

@@ -41,7 +41,7 @@ class OnboardingCoreConfig extends LitElement {
   @property() private _unitSystem!: ConfigUpdateValues["unit_system"];
   @property() private _timeZone!: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <p>
         ${this.onboardingLocalize(

src/onboarding/onboarding-create-user.ts

@@ -28,7 +28,7 @@ class OnboardingCreateUser extends LitElement {
   @property() private _loading = false;
   @property() private _errorMsg?: string = undefined;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
     <p>
       ${this.localize("ui.panel.page-onboarding.intro")}

src/onboarding/onboarding-integrations.ts

@@ -51,7 +51,7 @@ class OnboardingIntegrations extends LitElement {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._entries || !this._discovered) {
       return html``;
     }

src/onboarding/onboarding-loading.ts

@@ -9,7 +9,7 @@ import {
 
 @customElement("onboarding-loading")
 class OnboardingLoading extends LitElement {
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <div class="loader"></div>
     `;

src/panels/config/areas/dialog-area-registry-detail.ts

@@ -32,7 +32,7 @@ class DialogAreaDetail extends LitElement {
     await this.updateComplete;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._params) {
       return html``;
     }

src/panels/config/areas/ha-config-areas.ts

@@ -45,7 +45,7 @@ export class HaConfigAreas extends LitElement {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.hass || this._areas === undefined) {
       return html`
         <hass-loading-screen></hass-loading-screen>

src/panels/config/automation/ha-automation-editor.ts

@@ -45,7 +45,7 @@ export class HaAutomationEditor extends LitElement {
   @property() private _dirty?: boolean;
   @property() private _errors?: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <ha-app-layout has-scrolling-region>
         <app-header slot="header" fixed>

src/panels/config/automation/ha-automation-picker.ts

@@ -39,7 +39,7 @@ class HaAutomationPicker extends LitElement {
   @property() public isWide!: boolean;
   @property() public automations!: AutomationEntity[];
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <hass-subpage
         .showBackButton=${!this.isWide}

src/panels/config/automation/thingtalk/dialog-thingtalk.ts

@@ -58,7 +58,7 @@ class DialogThingtalk extends LitElement {
     this._opened = true;
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this._params) {
       return html``;
     }

src/panels/config/automation/thingtalk/ha-thingtalk-placeholders.ts

@@ -112,7 +112,7 @@ export class ThingTalkPlaceholders extends SubscribeMixin(LitElement) {
     }
   }
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     return html`
       <ha-paper-dialog
         modal

src/panels/config/cloud/account/cloud-alexa-pref.ts

@@ -23,7 +23,7 @@ export class CloudAlexaPref extends LitElement {
   @property() public cloudStatus?: CloudStatusLoggedIn;
   @property() private _syncing = false;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.cloudStatus) {
       return html``;
     }

src/panels/config/cloud/account/cloud-google-pref.ts

@@ -24,7 +24,7 @@ export class CloudGooglePref extends LitElement {
   @property() public hass?: HomeAssistant;
   @property() public cloudStatus?: CloudStatusLoggedIn;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.cloudStatus) {
       return html``;
     }

src/panels/config/cloud/account/cloud-remote-pref.ts

@@ -29,7 +29,7 @@ export class CloudRemotePref extends LitElement {
   @property() public hass?: HomeAssistant;
   @property() public cloudStatus?: CloudStatusLoggedIn;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (!this.cloudStatus) {
       return html``;
     }

src/panels/config/cloud/alexa/cloud-alexa.ts

@@ -72,7 +72,7 @@ class CloudAlexa extends LitElement {
     )
   );
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (this._entities === undefined) {
       return html`
         <hass-loading-screen></hass-loading-screen>

src/panels/config/cloud/google-assistant/cloud-google-assistant.ts

@@ -71,7 +71,7 @@ class CloudGoogleAssistant extends LitElement {
     )
   );
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     if (this._entities === undefined) {
       return html`
         <hass-loading-screen></hass-loading-screen>

src/panels/config/core/ha-config-core-form.ts

@@ -33,7 +33,7 @@ class ConfigCoreForm extends LitElement {
   @property() private _unitSystem!: ConfigUpdateValues["unit_system"];
   @property() private _timeZone!: string;
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const canEdit = ["storage", "default"].includes(
       this.hass.config.config_source
     );

src/panels/config/core/ha-config-name-form.ts

@@ -24,7 +24,7 @@ class ConfigNameForm extends LitElement {
 
   @property() private _name!: ConfigUpdateValues["location_name"];
 
-  protected render(): TemplateResult | void {
+  protected render(): TemplateResult {
     const canEdit = ["storage", "default"].includes(
       this.hass.config.config_source
     );