only add tip for autocomplete

Wire haJinjaHoverSource into ha-code-editor via CodeMirror hoverTooltip.
Two types of hover are now shown in jinja2/yaml mode:

- Hovering a function/filter/tag/expression name shows its signature,
  description, and a doc-link icon (non-tags only).
- Hovering a string-literal argument of a known HA Jinja function (e.g.
  states(), device_name(), area_entities()) shows the friendly name,
  current state, device, and area for entity_id arguments; the device
  name and area for device_id arguments; and the area name for area_id
  arguments. The same applies to states["entity_id"] subscripts.

The arg-value tooltip reuses CompletionItem / ha-code-editor-completion-items
(the same component used for autocomplete info popovers) via a new
ha-code-editor-jinja-arg-hover element. HA registry data is passed from
ha-code-editor via a HassArgHoverContext interface to keep jinja_ha_completions.ts
free of HomeAssistant type imports.

src/components/ha-code-editor-jinja-arg-hover.ts

@@ -0,0 +1,42 @@
+import { css, html, LitElement, nothing } from "lit";
+import { customElement, property } from "lit/decorators";
+import type { CompletionItem } from "./ha-code-editor-completion-items";
+import "./ha-code-editor-completion-items";
+
+@customElement("ha-code-editor-jinja-arg-hover")
+export class HaCodeEditorJinjaArgHover extends LitElement {
+  /** Bold heading shown above the items grid (e.g. entity/device/area name). */
+  @property({ attribute: false }) public heading?: string;
+
+  @property({ attribute: false }) public items: CompletionItem[] = [];
+
+  render() {
+    return html`
+      ${this.heading
+        ? html`<div class="heading">${this.heading}</div>`
+        : nothing}
+      <ha-code-editor-completion-items
+        .items=${this.items}
+      ></ha-code-editor-completion-items>
+    `;
+  }
+
+  static styles = css`
+    :host {
+      display: block;
+      padding: 6px 10px;
+      max-width: 360px;
+    }
+
+    .heading {
+      font-weight: var(--ha-font-weight-bold);
+      margin-bottom: 4px;
+    }
+  `;
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "ha-code-editor-jinja-arg-hover": HaCodeEditorJinjaArgHover;
+  }
+}

src/components/ha-code-editor-jinja-hover.ts

@@ -0,0 +1,98 @@
+import type { Completion } from "@codemirror/autocomplete";
+import { css, html, LitElement, nothing } from "lit";
+import { customElement, property } from "lit/decorators";
+import { mdiHelpCircleOutline } from "@mdi/js";
+import "./ha-svg-icon";
+
+@customElement("ha-code-editor-jinja-hover")
+export class HaCodeEditorJinjaHover extends LitElement {
+  @property({ attribute: false }) public completion!: Completion;
+
+  @property({ attribute: false }) public docUrl?: string;
+
+  render() {
+    const info =
+      typeof this.completion.info === "string"
+        ? this.completion.info
+        : undefined;
+
+    return html`
+      <div class="header">
+        <div class="sig">
+          <strong>${this.completion.label}</strong>
+          ${this.completion.detail
+            ? html`<span class="detail">(${this.completion.detail})</span>`
+            : nothing}
+        </div>
+        ${this.docUrl
+          ? html`<a
+              class="doc-link"
+              href=${this.docUrl}
+              target="_blank"
+              rel="noreferrer"
+              title="Open documentation"
+              ><ha-svg-icon .path=${mdiHelpCircleOutline}></ha-svg-icon
+            ></a>`
+          : nothing}
+      </div>
+      ${info ? html`<div class="desc">${info}</div>` : nothing}
+    `;
+  }
+
+  static styles = css`
+    :host {
+      display: block;
+      padding: 6px 10px;
+      max-width: 360px;
+      line-height: 1.5;
+    }
+
+    .header {
+      display: flex;
+      align-items: center;
+      gap: 6px;
+      margin-bottom: 4px;
+    }
+
+    .sig {
+      font-family: var(--ha-font-family-code);
+      font-size: 0.9em;
+      flex: 1;
+      min-width: 0;
+    }
+
+    .detail {
+      color: var(--secondary-text-color);
+    }
+
+    .doc-link {
+      flex-shrink: 0;
+      display: inline-flex;
+      align-items: center;
+      color: var(--secondary-text-color);
+      opacity: 0.7;
+      line-height: 1;
+    }
+
+    .doc-link:hover {
+      opacity: 1;
+      color: var(--primary-color);
+    }
+
+    .doc-link ha-svg-icon {
+      width: 16px;
+      height: 16px;
+    }
+
+    .desc {
+      font-size: 0.9em;
+      color: var(--secondary-text-color);
+    }
+  `;
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    "ha-code-editor-jinja-hover": HaCodeEditorJinjaHover;
+  }
+}

src/components/ha-code-editor.ts

@@ -36,9 +36,13 @@ import { computeAreaName } from "../common/entity/compute_area_name";
 import { computeFloorName } from "../common/entity/compute_floor_name";
 import { copyToClipboard } from "../common/util/copy-clipboard";
 import { haStyleScrollbar } from "../resources/styles";
-import type { JinjaArgType } from "../resources/jinja_ha_completions";
+import type {
+  JinjaArgType,
+  HassArgHoverContext,
+} from "../resources/jinja_ha_completions";
 import type { HomeAssistant } from "../types";
 import { showToast } from "../util/toast";
+import { documentationUrl } from "../util/documentation-url";
 import { labelsContext } from "../data/context";
 import type { LabelRegistryEntry } from "../data/label/label_registry";
 import "./ha-code-editor-completion-items";
@@ -326,6 +330,16 @@ export class HaCodeEditor extends ReactiveElement {
       this._loadedCodeMirror.tooltips({
         position: "absolute",
       }),
+      this._loadedCodeMirror.hoverTooltip(
+        (view, pos) =>
+          this._loadedCodeMirror!.haJinjaHoverSource(
+            view,
+            pos,
+            this.hass ? documentationUrl(this.hass, "") : undefined,
+            this.hass ? this._hassArgHoverContext() : undefined
+          ),
+        { hoverTime: 300 }
+      ),
       ...(this.placeholder ? [placeholder(this.placeholder)] : []),
     ];
 
@@ -575,6 +589,48 @@ export class HaCodeEditor extends ReactiveElement {
     }
   };
 
+  /**
+   * Builds a HassArgHoverContext from the current hass object so that
+   * haJinjaHoverSource can resolve entity / device / area friendly names
+   * without importing the full HomeAssistant type into the resource file.
+   */
+  private _hassArgHoverContext(): HassArgHoverContext {
+    const hass = this.hass!;
+    const labelMap: Record<
+      string,
+      { name: string; description?: string | null }
+    > = {};
+    for (const label of this._labels ?? []) {
+      labelMap[label.label_id] = {
+        name: label.name,
+        description: label.description,
+      };
+    }
+    return {
+      states: hass.states as HassArgHoverContext["states"],
+      devices: hass.devices as HassArgHoverContext["devices"],
+      areas: hass.areas as HassArgHoverContext["areas"],
+      floors: hass.floors as HassArgHoverContext["floors"],
+      entities: hass.entities as HassArgHoverContext["entities"],
+      labels: labelMap,
+      formatEntityState: (entityId) =>
+        hass.formatEntityState(hass.states[entityId]),
+      formatEntityName: (entityId) => {
+        const stateObj = hass.states[entityId];
+        return (
+          (stateObj?.attributes.friendly_name as string | undefined) ??
+          hass.entities[entityId]?.name ??
+          undefined
+        );
+      },
+      formatAttributeName: (entityId, attribute) =>
+        hass.formatEntityAttributeName(hass.states[entityId], attribute),
+      formatAttributeValue: (entityId, attribute) =>
+        hass.formatEntityAttributeValue(hass.states[entityId], attribute),
+      localize: (key) => hass.localize(key as never),
+    };
+  }
+
   private _renderInfo = (completion: Completion): CompletionInfo => {
     const key =
       typeof completion.apply === "string"

src/panels/config/developer-tools/template/developer-tools-template.ts

@@ -9,6 +9,7 @@ import "../../../../components/ha-button";
 import "../../../../components/ha-card";
 import "../../../../components/ha-code-editor";
 import "../../../../components/ha-spinner";
+import "../../../../components/ha-tip";
 import type { RenderTemplateResult } from "../../../../data/ws-templates";
 import { subscribeRenderTemplate } from "../../../../data/ws-templates";
 import { showConfirmationDialog } from "../../../../dialogs/generic/show-dialog-box";
@@ -158,6 +159,14 @@ class HaPanelDevTemplate extends LitElement {
               ${this.hass.localize("ui.common.clear")}
             </ha-button>
           </div>
+          <ha-tip .hass=${this.hass}>
+            ${this.hass.localize(
+              "ui.panel.config.developer-tools.tabs.templates.keyboard_tip",
+              {
+                autocomplete: html`<kbd>Ctrl</kbd>+<kbd>Space</kbd>`,
+              }
+            )}
+          </ha-tip>
         </ha-card>
 
         <ha-card
@@ -361,6 +370,22 @@ ${type === "object"
           color: var(--warning-color);
         }
 
+        ha-tip {
+          padding: 0 var(--ha-space-4) var(--ha-space-4);
+          display: block;
+        }
+
+        kbd {
+          display: inline-block;
+          font-family: var(--ha-font-family-code);
+          font-size: 0.85em;
+          padding: 1px 5px;
+          border: 1px solid var(--divider-color);
+          border-radius: var(--ha-border-radius-xs);
+          background-color: var(--secondary-background-color);
+          white-space: nowrap;
+        }
+
         @media all and (max-width: 870px) {
           .content ha-card {
             max-width: 100%;

src/resources/codemirror.ts

@@ -43,6 +43,7 @@ export {
   drawSelection,
   EditorView,
   highlightActiveLine,
+  hoverTooltip,
   keymap,
   lineNumbers,
   rectangularSelection,
@@ -70,9 +71,10 @@ export const closeBracketsOverride = Prec.highest(
 
 export {
   haJinjaCompletionSource,
+  haJinjaHoverSource,
   JINJA_FUNCTION_ARG_TYPES,
 } from "./jinja_ha_completions";
-export type { JinjaArgType } from "./jinja_ha_completions";
+export type { HassArgHoverContext, JinjaArgType } from "./jinja_ha_completions";
 export { closePercentBrace };
 
 export const langCompartment = new Compartment();

src/translations/en.json

@@ -3867,7 +3867,8 @@
               "no_listeners": "This template does not listen for any events and will not update automatically.",
               "listeners": "This template listens for the following state changed events:",
               "entity": "Entity",
-              "domain": "Domain"
+              "domain": "Domain",
+              "keyboard_tip": "Press {autocomplete} to trigger autocomplete, when your cursor is inside a function that supports it."
             },
             "statistics": {
               "title": "Statistics",