fix: add helpful suggestions to generator error messages (fixes #1728)

.changeset/fix-generate-error-message.md

@@ -0,0 +1,5 @@
+---
+"@asyncapi/cli": patch
+---
+
+Add helpful suggestions to generator error messages (fixes #1728)

src/apps/cli/commands/generate/fromTemplate.ts

@@ -26,7 +26,7 @@
     template: Args.string({ description: '- Name of the generator template like for example @asyncapi/html-template or https://github.com/asyncapi/html-template', required: false }),
   };
 
   async run() {
     const { args, flags } = await this.parse(Template); // NOSONAR
     const interactive = !flags['no-interactive'];
     let asyncapi = args['asyncapi'] ?? '';
@@ -88,7 +88,24 @@
       interactive,
     );
     if (!result.success) {
-      throw new GeneratorError(new Error(result.error));
+      const errorMsg = result.error || 'Unknown error';
+      const suggestions: string[] = [];
+
+      if (errorMsg.includes('ENOENT') || errorMsg.includes('not found') || errorMsg.includes('Cannot find')) {
+        suggestions.push('The template may not be installed. Try installing it first with: npm install <template-name>');
+      }
+      if (errorMsg.includes('invalid') || errorMsg.includes('parse') || errorMsg.includes('syntax')) {
+        suggestions.push('The AsyncAPI document may be invalid or unsupported. Verify it with: asyncapi validate <document>');
+      }
+      if (errorMsg.includes('E404') || errorMsg.includes('404')) {
+        suggestions.push('The template was not found on npm. Check the template name and try again.');
+      }
+
+      const fullMessage = suggestions.length > 0
+        ? `${errorMsg}\n\nPossible causes:\n${suggestions.map(s => `  - ${s}`).join('\n')}`
+        : errorMsg;
+
+      throw new GeneratorError(new Error(fullMessage));
     }
 
     // Output logs in non-interactive mode