Fix: Display warning when a loader isn't defined in the webpack config for a custom block (instead of crashing)

Don't put anything into the output file if no loaders are configured for custom blocks

Author: Andre Asselin

lib/loader.js

@@ -275,15 +275,25 @@ module.exports = function (content) {
 
   // add requires for customBlocks
   if (parts.customBlocks && parts.customBlocks.length) {
-    output += '\n/* customBlocks */\n'
+    var addedPrefix = false
+
     parts.customBlocks.forEach(function (customBlock, i) {
-      // require customBlock
-      customBlock.src = customBlock.attrs.src
-      var requireString = customBlock.src
-        ? getRequireForImport(customBlock.type, customBlock)
-        : getRequire(customBlock.type, customBlock, i)
+      if (!loaders[customBlock.type]) {
+        loaderContext.emitWarning('Loader for custom block type "' + customBlock.type + '" not found in webpack configuration')
+      } else {
+        // require customBlock
+        customBlock.src = customBlock.attrs.src
+        var requireString = customBlock.src
+          ? getRequireForImport(customBlock.type, customBlock)
+          : getRequire(customBlock.type, customBlock, i)
+
+        if (!addedPrefix) {
+          output += '\n/* customBlocks */\n'
+          addedPrefix = true
+        }
 
-      output += requireString
+        output += requireString
+      }
     })
   }