Add ha-form context (#12062)

src/components/ha-selector/ha-selector-attribute.ts

@@ -1,9 +1,10 @@
 import "../entity/ha-entity-attribute-picker";
-import { html, LitElement } from "lit";
+import { html, LitElement, PropertyValues } from "lit";
 import { customElement, property } from "lit/decorators";
 import { AttributeSelector } from "../../data/selector";
 import { SubscribeMixin } from "../../mixins/subscribe-mixin";
 import { HomeAssistant } from "../../types";
+import { fireEvent } from "../../common/dom/fire_event";
 
 @customElement("ha-selector-attribute")
 export class HaSelectorAttribute extends SubscribeMixin(LitElement) {
@@ -17,11 +18,16 @@ export class HaSelectorAttribute extends SubscribeMixin(LitElement) {
 
   @property({ type: Boolean }) public disabled = false;
 
+  @property() public context?: {
+    filter_entity?: string;
+  };
+
   protected render() {
     return html`
       <ha-entity-attribute-picker
         .hass=${this.hass}
-        .entityId=${this.selector.attribute.entity_id}
+        .entityId=${this.selector.attribute.entity_id ||
+        this.context?.filter_entity}
         .value=${this.value}
         .label=${this.label}
         .disabled=${this.disabled}
@@ -29,6 +35,47 @@ export class HaSelectorAttribute extends SubscribeMixin(LitElement) {
       ></ha-entity-attribute-picker>
     `;
   }
+
+  protected updated(changedProps: PropertyValues): void {
+    super.updated(changedProps);
+    if (
+      // No need to filter value if no value
+      !this.value ||
+      // Only adjust value if we used the context
+      this.selector.attribute.entity_id ||
+      // Only check if context has changed
+      !changedProps.has("context")
+    ) {
+      return;
+    }
+
+    const oldContext = changedProps.get("context") as this["context"];
+
+    if (
+      !this.context ||
+      oldContext?.filter_entity === this.context.filter_entity
+    ) {
+      return;
+    }
+
+    // Validate that that the attribute is still valid for this entity, else unselect.
+    let invalid = false;
+    if (this.context.filter_entity) {
+      const stateObj = this.hass.states[this.context.filter_entity];
+
+      if (!(stateObj && this.value in stateObj.attributes)) {
+        invalid = true;
+      }
+    } else {
+      invalid = this.value !== undefined;
+    }
+
+    if (invalid) {
+      fireEvent(this, "value-changed", {
+        value: undefined,
+      });
+    }
+  }
 }
 
 declare global {