feat: 🎸 Scripts without source will cause promise rejection

Author: PS

Diff for: packages/integration/src/__tests__/indexSpec.js

@@ -282,5 +282,35 @@ describe('Merkur component', () => {
           done('promise was rejected');
         });
     });
+
+    it('should throw an error, if script have no source', (done) => {
+      loadScriptAssets(
+        [
+          {
+            name: 'optional.js',
+            type: 'script',
+            source: {},
+            optional: true,
+          },
+          {
+            name: 'nosource.js',
+            type: 'script',
+            source: {},
+          },
+        ],
+        rootElement
+      )
+        .then(() => {
+          done('did not reject');
+        })
+        .catch((error) => {
+          expect(error.message).toBe(
+            "Asset 'nosource.js' is missing ES variant and could not be loaded."
+          );
+          expect(error.asset).toBeTruthy();
+
+          done();
+        });
+    });
   });
 });

Diff for: packages/integration/src/index.js

@@ -90,7 +90,7 @@ function loadStyleAssets(assets, root = document.head) {
   return Promise.all(stylesToRender.map((asset) => _loadStyle(asset, root)));
 }
 
-function loadScriptAssets(assets, root = document.head) {
+async function loadScriptAssets(assets, root = document.head) {
   const scriptElements = root.querySelectorAll('script');
   const scriptsToRender = assets.reduce((scripts, asset) => {
     const { source } = asset;
@@ -110,9 +110,16 @@ function loadScriptAssets(assets, root = document.head) {
       }
 
       if (!_asset.source) {
-        console.warn(
-          `Asset '${_asset.name}' is missing ES variant and could not be loaded.`
-        );
+        const message = `Asset '${_asset.name}' is missing ES variant and could not be loaded.`;
+
+        if (!_asset.optional) {
+          const error = new Error(message);
+          error.asset = _asset;
+
+          throw error;
+        }
+
+        console.warn(message);
         return scripts;
       }
     }