[LiveComponent] Return empty string for data-value="" instead of falling back to null

Author: mercuryseries

src/LiveComponent/assets/dist/live_controller.js

@@ -377,7 +377,7 @@ function getValueFromElement(element, valueStore) {
     }
     return element.value;
   }
-  if (element.dataset.value) {
+  if (element.hasAttribute("data-value")) {
     return element.dataset.value;
   }
   if ("value" in element) {

src/LiveComponent/assets/src/dom_utils.ts

@@ -51,7 +51,7 @@ export function getValueFromElement(element: HTMLElement, valueStore: ValueStore
     }
 
     // element is some other element
-    if (element.dataset.value) {
+    if (element.hasAttribute('data-value')) {
         return element.dataset.value;
     }
 

src/LiveComponent/assets/test/unit/dom_utils.test.ts

@@ -110,6 +110,40 @@ describe('getValueFromElement', () => {
 
         expect(getValueFromElement(div, createStore())).toEqual('the_value_from_attribute');
     });
+
+    it('Returns empty string for data-value=""', () => {
+        const btn = document.createElement('button');
+        // simulate the attribute explicitly present but empty
+        btn.dataset.value = '';
+        // also set a value on the button to ensure data-value takes precedence
+        btn.value = 'should_not_be_used';
+        expect(getValueFromElement(btn, createStore())).toBe('');
+    });
+
+    it('Returns "0" for data-value="0" (falsy but valid)', () => {
+        const el = document.createElement('div');
+        el.dataset.value = '0';
+        expect(getValueFromElement(el, createStore())).toBe('0');
+    });
+
+    it('Prefers data-value over value attribute when both are present', () => {
+        const el = document.createElement('div');
+        el.dataset.value = 'from_data_value';
+        el.setAttribute('value', 'from_value_attribute');
+        expect(getValueFromElement(el, createStore())).toBe('from_data_value');
+    });
+
+    it('Falls back to value attribute when data-value is absent', () => {
+        const el = document.createElement('div');
+        el.setAttribute('value', '');
+        // No data-value set
+        expect(getValueFromElement(el, createStore())).toBe('');
+    });
+
+    it('Returns null when neither data-value nor value attribute nor value property is present', () => {
+        const el = document.createElement('div');
+        expect(getValueFromElement(el, createStore())).toBe(null);
+    });
 });
 
 describe('setValueOnElement', () => {