eta template render: working versions (tested 2026-10-16)

{
  "name": "eta-template-render",
  "private": true,
  "type": "module",
  "scripts": {
    "test": "node --import tsx --test test/*.test.ts"
  },
  "dependencies": {
    "eta": "4.6.0"
  },
  "devDependencies": {
    "@types/node": "26.6.5",
    "tsx": "4.23.15"
  }
}

import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
import { tmpdir } from "node:os";
import { join } from "node:path";
import { Eta } from "eta";

export type LayoutData = {
  title: string;
  body: string;
};

const LAYOUT = [
  "<!doctype html>",
  "<html>",
  "<head><title><%= it.title %></title></head>",
  "<body>",
  '<%~ include("./header.eta", { title: it.title }) %>',
  "<main><%~ it.body %></main>",
  "</body>",
  "</html>",
].join("\n");

const HEADER = "<header><h1><%= it.title %></h1></header>";

export function createViewsDir(): string {
  const dir = mkdtempSync(join(tmpdir(), "eta-views-"));
  writeFileSync(join(dir, "layout.eta"), LAYOUT, "utf8");
  writeFileSync(join(dir, "header.eta"), HEADER, "utf8");
  return dir;
}

export function createEta(views: string): Eta {
  return new Eta({ views, autoEscape: true, varName: "it", cache: false });
}

export function renderLayout(eta: Eta, data: LayoutData): string {
  return eta.render("layout.eta", data);
}

export function renderInline(eta: Eta, template: string, data: Record<string, unknown>): string {
  return eta.renderString(template, data);
}

export function cleanupViews(dir: string): void {
  rmSync(dir, { recursive: true, force: true });
}

import { after, test } from "node:test";
import assert from "node:assert/strict";
import {
  cleanupViews,
  createEta,
  createViewsDir,
  renderInline,
  renderLayout,
} from "../src/render.ts";

const views = createViewsDir();
const eta = createEta(views);

after(() => {
  cleanupViews(views);
});

test("renders a layout with a partial include", () => {
  const html = renderLayout(eta, { title: "Home", body: "<p>Welcome</p>" });
  assert.match(html, /<title>Home<\/title>/);
  assert.match(html, /<header><h1>Home<\/h1><\/header>/);
  assert.match(html, /<main><p>Welcome<\/p><\/main>/);
});

test("auto-escapes interpolated values in layout and partial", () => {
  const html = renderLayout(eta, { title: "Home <b> & co", body: "<p>ok</p>" });
  assert.match(html, /Home &lt;b/);
  assert.match(html, /&amp; co/);
  assert.doesNotMatch(html, /<b>/);
});

test("renderString escapes data", () => {
  const out = renderInline(eta, "<p><%= it.msg %></p>", { msg: "a & b < c" });
  assert.equal(out, "<p>a &amp; b &lt; c</p>");
});