feat(esl-utils): extend attr decorator with inherit option

src/modules/esl-utils/decorators/attr.ts

@@ -1,6 +1,6 @@
 import {identity, resolveProperty} from '../misc/functions';
 import {parseString, toKebabCase} from '../misc/format';
-import {getAttr, setAttr} from '../dom/attr';
+import {getAttr, getClosestAttr, setAttr} from '../dom/attr';
 
 import type {PropertyProvider} from '../misc/functions';
 import type {ESLAttributeDecorator} from '../dom/attr';
@@ -15,6 +15,17 @@ type AttrDescriptor<T = string> = {
   name?: string;
   /** Create getter only */
   readonly?: boolean;
+  /**
+   * Specifies the attribute inheritance behavior.
+   * If `inherit` is set to `true`, the attribute will inherit the value from the same-named attribute of the closest parent element in the DOM tree.
+   * For instance, `@attr({inherit: true}) ignore;` will look for an `ignore` attribute in the parent elements if it's not defined in the current element.
+   * If `dataAttr` is also true, it will search for `data-ignore` instead.
+   *
+   * If `inherit` is set to a string, it will use this string as the attribute name to search for in the parent elements.
+   * For example, `@attr({inherit: 'alt-ignore'}) ignore;` will first look for its own `ignore` attribute (or 'data-ignore' if `dataAttr` is true),
+   * and if not found, it will look for an `alt-ignore` attribute in the parent elements.
+   */
+  inherit?: boolean | string;
   /** Use data-* attribute */
   dataAttr?: boolean;
   /** Default property value. Used if no attribute is present on the element. Empty string by default. Supports provider function. */
@@ -36,14 +47,14 @@ const buildAttrName =
 export const attr = <T = string>(config: AttrDescriptor<T> = {}): ESLAttributeDecorator => {
   return (target: ESLDomElementTarget, propName: string): any => {
     const attrName = buildAttrName(config.name || propName, !!config.dataAttr);
+    const inheritAttrName = typeof config.inherit === 'string' ? config.inherit : attrName;
 
     function get(): T | null {
-      const val = getAttr(this, attrName);
-      if (val === null && 'defaultValue' in config) {
-        return resolveProperty(config.defaultValue, this) as T;
-      }
+      const val = config.inherit ? getAttr(this, attrName) || getClosestAttr(this, inheritAttrName) : getAttr(this, attrName);
+      if (val === null && 'defaultValue' in config) return resolveProperty(config.defaultValue, this) as T;
       return (config.parser || parseString as AttrParser<any>)(val);
     }
+
     function set(value: T): void {
       setAttr(this, attrName, (config.serializer as AttrSerializer<any> || identity)(value));
     }

src/modules/esl-utils/decorators/test/attr.test.ts

@@ -1,5 +1,6 @@
 import '../../../../polyfills/es5-target-shim';
 import {attr} from '../attr';
+import {ESLTestTemplate} from '../../test/template';
 
 describe('Decorator: attr', () => {
 
@@ -106,6 +107,121 @@ describe('Decorator: attr', () => {
     expect(el.defProvider).toBe('');
   });
 
+  describe('inherit parameter', () => {
+
+    class ThirdElement extends HTMLElement {
+      @attr({inherit: 'box'})
+      public container: string;
+      @attr({inherit: 'parent', dataAttr: true})
+      public ignore: string;
+      @attr({inherit: true})
+      public disallow: string;
+      @attr({inherit: true, dataAttr: true})
+      public allow: string;
+    }
+    customElements.define('third-el', ThirdElement);
+
+    class SecondElement extends HTMLElement {}
+    customElements.define('second-el', SecondElement);
+
+    const SCOPE: any = {
+      firstEl: '#first-el',
+      secondEl: '#second-el',
+      thirdEl: '#third-el',
+    };
+    const TEMPLATE = ESLTestTemplate.create(`
+      <div id="first-el">
+        <second-el id="second-el">
+          <third-el id="third-el"></third-el>
+        </second-el>
+      </div>
+    `, SCOPE).bind('beforeeach');
+
+    describe('Inherit searches for the closest element with explicitly declared name', () => {
+      //  @attr({inherit: 'box'}) public container: string;
+      test('The attribute inherit the value from own same-named attribute', () => {
+        TEMPLATE.$thirdEl.setAttribute('container', 'value');
+        expect(TEMPLATE.$thirdEl.container).toBe('value');
+      });
+      test('Own attribute setter changes the own value', () => {
+        TEMPLATE.$thirdEl.container = 'container';
+        expect(TEMPLATE.$thirdEl.container).toBe('container');
+      });
+      test('The value resolves from the closest element (custom-element) in DOM', () => {
+        TEMPLATE.$secondEl.setAttribute('box', 'carousel');
+        expect(TEMPLATE.$thirdEl.container).toBe('carousel');
+      });
+      test('The value resolves from the closest element (non-custom-element) in DOM', () => {
+        TEMPLATE.$firstEl.setAttribute('box', 'slide');
+        expect(TEMPLATE.$thirdEl.container).toBe('slide');
+      });
+      test('Elements with declared inherit are absent in DOM and returns empty string', () => {
+        expect(TEMPLATE.$thirdEl.container).toBe('');
+      });
+    });
+
+    describe('Inherit searches for the closest element with explicitly declared data attribute name', () => {
+      // @attr({inherit: 'parent', dataAttr: true}) public ignore: string;
+      test('The attribute inherit the value from the same-named data-attribute', () => {
+        TEMPLATE.$thirdEl.setAttribute('data-ignore', 'swipe');
+        expect(TEMPLATE.$thirdEl.ignore).toBe('swipe');
+      });
+      test('Own attribute setter changes the own value', () => {
+        TEMPLATE.$thirdEl.ignore = 'touch';
+        expect(TEMPLATE.$thirdEl.ignore).toBe('touch');
+      });
+      test('The value resolves from the closest element (custom-element) in DOM', () => {
+        TEMPLATE.$secondEl.setAttribute('parent', 'close');
+        expect(TEMPLATE.$thirdEl.ignore).toBe('close');
+      });
+      test('The value resolves from the closest element (non-custom-element) in DOM', () => {
+        TEMPLATE.$firstEl.setAttribute('parent', 'open');
+        expect(TEMPLATE.$thirdEl.ignore).toBe('open');
+      });
+      test('Elements with declared inherit are absent in DOM and returns empty string', () => {
+        expect(TEMPLATE.$thirdEl.ignore).toBe('');
+      });
+    });
+
+    describe('Inherit searches for the closest element with the same attribute name in DOM', () => {
+      // @attr({inherit: true}) public disallow: string;
+      test('The attribute inherit the value from the same attribute name', () => {
+        TEMPLATE.$thirdEl.disallow = 'scroll';
+        expect(TEMPLATE.$thirdEl.disallow).toBe('scroll');
+      });
+      test('The value resolves from the closest element (custom-element) in DOM with the same attribute name', () => {
+        TEMPLATE.$secondEl.setAttribute('disallow', 'activator');
+        expect(TEMPLATE.$thirdEl.disallow).toBe('activator');
+      });
+      test('The value resolves from the closest element (non-custom-element) in DOM with the same attribute name', () => {
+        TEMPLATE.$firstEl.setAttribute('disallow', 'deactivator');
+        expect(TEMPLATE.$thirdEl.disallow).toBe('deactivator');
+      });
+      test('Elements with declared inherit are absent in DOM and returns empty string', () => {
+        expect(TEMPLATE.$thirdEl.disallow).toBe('');
+      });
+    });
+
+    describe('Inherit searches for the closest element with the same data-attribute name in DOM', () => {
+      // @attr({inherit: true, dataAttr: true}) public allow: string;
+      test('The attribute inherit the value from the same attribute name', () => {
+        TEMPLATE.$thirdEl.allow = 'option';
+        expect(TEMPLATE.$thirdEl.allow).toBe('option');
+      });
+      test('The value resolves from the closest element (custom-element) in DOM with the same data-attribute name', () => {
+        TEMPLATE.$secondEl.setAttribute('data-allow', 'scroll');
+        expect(TEMPLATE.$thirdEl.allow).toBe('scroll');
+      });
+      test('The value resolves from the closest element (non-custom-element) in DOM with the same data-attribute name', () => {
+        TEMPLATE.$firstEl.setAttribute('data-allow', 'swipe');
+        expect(TEMPLATE.$thirdEl.allow).toBe('swipe');
+      });
+      test('Elements with declared inherit are absent in DOM and returns empty string', () => {
+        expect(TEMPLATE.$thirdEl.allow).toBe('');
+      });
+    });
+  });
+
   afterAll(() => {
     document.body.removeChild(el);
   });

src/modules/esl-utils/dom/attr.ts

@@ -35,3 +35,10 @@ export function setAttr($el: ESLAttributeTarget, name: string, value: undefined
     $el.setAttribute(name, value === true ? '' : value);
   }
 }
+
+/** Gets attribute value from the closest element with group behavior settings */
+export function getClosestAttr($el: ESLAttributeTarget, attrName: string): string | null {
+  if (!($el = resolveDomTarget($el))) return null;
+  const $closest = $el.closest(`[${attrName}]`);
+  return $closest ? $closest.getAttribute(attrName) : null;
+}

src/modules/esl-utils/dom/test/attr.test.ts

@@ -1,4 +1,4 @@
-import {hasAttr, getAttr, setAttr} from '../attr';
+import {hasAttr, getAttr, setAttr, getClosestAttr} from '../attr';
 
 describe('Attribute', () => {
   const attrName = 'test-attr';
@@ -118,4 +118,28 @@ describe('Attribute', () => {
       expect($el3.getAttribute(attrName)).toBe(attrValue);
     });
   });
+
+
+  describe('getClosestAttr', () => {
+    const $el = document.createElement('div');
+    $el.setAttribute(attrName, attrValue);
+
+    const $parent = document.createElement('div');
+    const $parentName = 'parent-attr';
+    const $parentValue = 'parent-value';
+    $parent.setAttribute($parentName, $parentValue);
+
+    $parent.append($el);
+    document.body.append($parent);
+
+    test('finds indicated attribute on this element', () => {
+      expect(getClosestAttr($el, attrName)).toBe(attrValue);
+    });
+    test('finds indicated attribute on closest parent in DOM', () => {
+      expect(getClosestAttr($el, $parentName)).toBe($parentValue);
+    });
+    test('returns null in case indicated attribute is absent in DOM', () => {
+      expect(getClosestAttr($el, 'name')).toBe(null);
+    });
+  });
 });