Preserve supported MJML button appearance on import

packages/email-renderer/test/mjml-button-import.test.ts

@@ -0,0 +1,37 @@
+import { expect, test } from "bun:test";
+import type { BlockNode } from "@wrnexus/blocks";
+import { importMjml, renderEmail } from "../src/index.ts";
+
+const source = (attributes: string) => `<mjml><mj-body><mj-section><mj-column><mj-button href="https://example.com/?a=1&amp;b=2" ${attributes}>Buy &amp; save &#33;</mj-button></mj-column></mj-section></mj-body></mjml>`;
+const findButton = (node: BlockNode): BlockNode | undefined => node.type === "content.button" ? node : Object.values(node.slots).flat().map(findButton).find(Boolean);
+
+test("imported button preserves supported appearance and escaped label/link across export", async () => {
+  let id = 0;
+  const imported = importMjml(source('align="right" background-color="#123456" color="#abcdef" font-size="22px" font-weight="400" border-radius="12px"'), { id: () => `n${++id}` });
+  expect(imported.ok).toBe(true);
+  if (!imported.ok) return;
+  const button = findButton(imported.value.root)!;
+  expect(button.props).toEqual({ label: "Buy & save !", href: "https://example.com/?a=1&b=2" });
+  expect(button.styles).toEqual({ textAlign: { base: "right" }, backgroundColor: { base: "#123456" }, color: { base: "#abcdef" }, fontSize: { base: "22px" }, fontWeight: { base: "400" }, borderRadius: { base: "12px" } });
+  const rendered = await renderEmail(imported.value, { mjml: true });
+  expect(rendered.ok).toBe(true);
+  if (!rendered.ok) return;
+  expect(rendered.value.parts.html.content).toContain("font-size:22px;font-weight:400;border-radius:12px");
+  expect(rendered.value.parts.text.content).toContain("Buy & save !");
+  const again = importMjml(rendered.value.exports!.mjml!, { id: () => `n${++id}` });
+  expect(again.ok).toBe(true);
+  if (again.ok) {
+    const next = findButton(again.value.root)!;
+    expect(next.props).toEqual(button.props);
+    expect(next.styles).toEqual(button.styles);
+  }
+});
+
+test("unsupported or unsafe button attributes produce explicit diagnostics", () => {
+  for (const attributes of ['color="red;position:fixed"', 'align="justify"', 'font-size="expression(1)"', 'onclick="alert(1)"', 'padding="20px"']) {
+    let id = 0;
+    const result = importMjml(source(attributes), { id: () => `n${++id}` });
+    expect(result.ok).toBe(false);
+    if (!result.ok) expect(result.errors.some(error => error.code === "mjml.button-attribute")).toBe(true);
+  }
+});