fix(email): validate MJML before exposing exports

packages/email-renderer/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@wrnexus/email-renderer",
-  "version": "0.1.26",
+  "version": "0.1.27",
   "type": "module",
   "description": "WRNexus block email renderers with HTML, text, AMP Email, and MJML interoperability.",
   "exports": {

packages/email-renderer/src/email.ts

@@ -13,6 +13,7 @@ import {
   type Result,
 } from "@wrnexus/blocks";
 import { emailCoreBlocks, ampLayoutCss } from "./blocks.ts";
+import { validateMjml } from "./mjml.ts";
 
 interface AmpValidationError {
   severity: string;
@@ -168,7 +169,13 @@ export async function renderEmail(
     warnings,
     assets: [],
   };
-  if (mjmlResult?.ok) bundle.exports = { mjml: mjmlResult.value.content };
+  if (mjmlResult?.ok) {
+    const diagnostics = await validateMjml(mjmlResult.value.content);
+    if (!diagnostics.length) bundle.exports = { mjml: mjmlResult.value.content };
+    else warnings.push(...diagnostics.map(diagnostic => ({ ...diagnostic, severity: "warning" as const })));
+  } else if (mjmlResult) {
+    warnings.push(...mjmlResult.errors.map(diagnostic => ({ ...diagnostic, severity: "warning" as const })));
+  }
   if (options.amp) {
     const amp = await renderTree(source, emailKind, registry, { ...base, target: "ampEmail", data: options.variables });
     if (amp.ok) {

packages/email-renderer/test/root-mjml.test.ts

@@ -5,6 +5,17 @@ import { renderEmail, validateMjml } from "../src/index.ts";
 const text = (id: string): BlockNode => ({ id, type: "content.text", version: 1, props: { text: id }, styles: {}, slots: {} });
 const columns = (id: string): BlockNode => ({ id, type: "layout.columns", version: 1, props: {}, styles: {}, slots: { columns: [0, 1].map(index => ({ id: `${id}-${index}`, type: "layout.column", version: 1, props: { width: "50%" }, styles: {}, slots: { content: [text(`${id}-text-${index}`)] } })) } });
 
+test("invalid nested MJML is diagnosed and omitted while HTML and text remain usable", async () => {
+  const document: BlockDocument = { schemaVersion: 1, kind: "email", meta: { subject: "Nested", lang: "en" }, theme: { tokens: {} }, root: { id: "root", type: "layout.email-document", version: 1, props: {}, styles: {}, slots: { content: [{ id: "outer", type: "layout.section", version: 1, props: {}, styles: {}, slots: { content: [{ id: "inner", type: "layout.section", version: 1, props: {}, styles: {}, slots: { content: [text("Retained nested content")] } }] } }] } } };
+  const rendered = await renderEmail(document, { mjml: true });
+  expect(rendered.ok).toBe(true);
+  if (!rendered.ok) return;
+  expect(rendered.value.exports?.mjml).toBeUndefined();
+  expect(rendered.value.warnings.some(warning => warning.code === "mjml.validation")).toBe(true);
+  expect(rendered.value.parts.html.content).toContain("Retained nested content");
+  expect(rendered.value.parts.text.content).toContain("Retained nested content");
+});
+
 test("root content and separate column rows produce valid ordered MJML without changing the document", async () => {
   const document: BlockDocument = { schemaVersion: 1, kind: "email", meta: { subject: "Root blocks", lang: "en" }, theme: { tokens: {} }, root: { id: "root", type: "layout.email-document", version: 1, props: {}, styles: {}, slots: { content: [text("intro"), columns("first"), columns("second"), { id: "cta", type: "content.button", version: 1, props: { label: "Act", href: "https://example.com" }, styles: {}, slots: {} }, text("end")] } } };
   const before = structuredClone(document);