Add ha-form context

gallery/src/pages/components/ha-form.ts

@@ -139,6 +139,7 @@ const SCHEMAS: {
       {
         name: "Attribute",
         selector: { attribute: { entity_id: "" } },
+        context: { filter_entity: "entity" },
       },
       { name: "Device", selector: { device: {} } },
       { name: "Duration", selector: { duration: {} } },

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

@@ -106,6 +106,7 @@ export class HaForm extends LitElement implements HaFormElement {
                   .disabled=${this.disabled}
                   .helper=${this._computeHelper(item)}
                   .required=${item.required || false}
+                  .context=${this._generateContext(item)}
                 ></ha-selector>`
               : dynamicElement(`ha-form-${item.type}`, {
                   schema: item,
@@ -115,13 +116,28 @@ export class HaForm extends LitElement implements HaFormElement {
                   hass: this.hass,
                   computeLabel: this.computeLabel,
                   computeHelper: this.computeHelper,
+                  context: this._generateContext(item),
                 })}
           `;
         })}
       </div>
     `;
   }
 
+  private _generateContext(
+    schema: HaFormSchema
+  ): Record<string, any> | undefined {
+    if (!schema.context) {
+      return undefined;
+    }
+
+    const context = {};
+    for (const [context_key, data_key] of Object.entries(schema.context)) {
+      context[context_key] = this.data[data_key];
+    }
+    return context;
+  }
+
   protected createRenderRoot() {
     const root = super.createRenderRoot();
     // attach it as soon as possible to make sure we fetch all events.

src/components/ha-form/types.ts

@@ -24,6 +24,7 @@ export interface HaFormBaseSchema {
     // This value will be set initially when form is loaded
     suggested_value?: HaFormData;
   };
+  context?: Record<string, string>;
 }
 
 export interface HaFormGridSchema extends HaFormBaseSchema {

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) {
@@ -17,18 +18,64 @@ 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}
         allow-custom-value
       ></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 {

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

@@ -42,6 +42,8 @@ export class HaSelector extends LitElement {
 
   @property({ type: Boolean }) public required = true;
 
+  @property() public context?: Record<string, any>;
+
   public focus() {
     this.shadowRoot?.getElementById("selector")?.focus();
   }
@@ -61,6 +63,7 @@ export class HaSelector extends LitElement {
         disabled: this.disabled,
         required: this.required,
         helper: this.helper,
+        context: this.context,
         id: "selector",
       })}
     `;

src/data/selector.ts

@@ -31,7 +31,7 @@ export interface EntitySelector {
 
 export interface AttributeSelector {
   attribute: {
-    entity_id: string;
+    entity_id?: string;
   };
 }