fix: hmr runtime on preloaded stylesheet link (#686)

Author: alexander-akait

src/hmr/hotModuleReplacement.js

@@ -108,11 +108,19 @@ function updateCss(el, url) {
   newEl.isLoaded = false;
 
   newEl.addEventListener('load', () => {
+    if (newEl.isLoaded) {
+      return;
+    }
+
     newEl.isLoaded = true;
     el.parentNode.removeChild(el);
   });
 
   newEl.addEventListener('error', () => {
+    if (newEl.isLoaded) {
+      return;
+    }
+
     newEl.isLoaded = true;
     el.parentNode.removeChild(el);
   });

test/HMR.test.js

@@ -306,4 +306,29 @@ describe('HMR', () => {
       done();
     }, 100);
   });
+
+  it('should not remove old link when new link is loaded twice', (done) => {
+    const link = document.createElement('link');
+
+    link.innerHTML = '<link rel="preload stylesheet" href="./dist/main.css" />';
+    document.head.appendChild(link);
+    document.head.removeChild = jest.fn();
+
+    const update = hotModuleReplacement('./dist/main.css', {});
+
+    update();
+
+    setTimeout(() => {
+      const links = Array.prototype.slice.call(
+        document.querySelectorAll('link')
+      );
+
+      links[1].dispatchEvent(getLoadEvent());
+      links[1].dispatchEvent(getLoadEvent());
+
+      expect(document.head.removeChild).toHaveBeenCalledTimes(1);
+
+      done();
+    }, 100);
+  });
 });

test/cases/hmr/expected/webpack-4/main.js

@@ -987,11 +987,19 @@ function updateCss(el, url) {
   newEl.isLoaded = false;
 
   newEl.addEventListener('load', () => {
+    if (newEl.isLoaded) {
+      return;
+    }
+
     newEl.isLoaded = true;
     el.parentNode.removeChild(el);
   });
 
   newEl.addEventListener('error', () => {
+    if (newEl.isLoaded) {
+      return;
+    }
+
     newEl.isLoaded = true;
     el.parentNode.removeChild(el);
   });

test/cases/hmr/expected/webpack-5/main.js

@@ -129,11 +129,19 @@ function updateCss(el, url) {
   newEl.isLoaded = false;
 
   newEl.addEventListener('load', () => {
+    if (newEl.isLoaded) {
+      return;
+    }
+
     newEl.isLoaded = true;
     el.parentNode.removeChild(el);
   });
 
   newEl.addEventListener('error', () => {
+    if (newEl.isLoaded) {
+      return;
+    }
+
     newEl.isLoaded = true;
     el.parentNode.removeChild(el);
   });