modify nunjucks parsing to stop parsing to string as [Object object]

Author: cpinn

js/src/template/nunjucks-env.ts

@@ -1,12 +1,26 @@
 import { nunjucks } from "./nunjucks";
-import type { Environment as NunjucksEnvironment } from "nunjucks";
+import type {
+  Environment as NunjucksEnvironment,
+  ConfigureOptions,
+} from "nunjucks";
 import { SyncLazyValue } from "../util";
 
 const createNunjucksEnv = (throwOnUndefined: boolean): NunjucksEnvironment => {
-  return new nunjucks.Environment(null, {
-    autoescape: true,
+  const options: ConfigureOptions & { finalize?: (val: unknown) => unknown } = {
+    autoescape: false,
     throwOnUndefined,
-  });
+    // Finalize function is called for every variable output
+    // This automatically JSON.stringify's objects, similar to the custom Mustache's escape function
+    finalize: (val: unknown) => {
+      if (typeof val === "object" && val !== null) {
+        return JSON.stringify(val);
+      }
+      return val;
+    },
+  };
+
+  const env = new nunjucks.Environment(null, options);
+  return env;
 };
 
 const nunjucksEnv = new SyncLazyValue<NunjucksEnvironment>(() =>

js/src/template/nunjucks-render.test.ts

@@ -1,19 +1,14 @@
 import { describe, test, expect } from "vitest";
 import { lintTemplate } from "./nunjucks-utils";
 import { nunjucks } from "./nunjucks";
+import { getNunjucksEnv } from "./nunjucks-env";
 
 function getEnv() {
-  return new nunjucks.Environment(null, {
-    autoescape: true,
-    throwOnUndefined: false,
-  });
+  return getNunjucksEnv(false);
 }
 
 function getStrictEnv() {
-  return new nunjucks.Environment(null, {
-    autoescape: true,
-    throwOnUndefined: true,
-  });
+  return getNunjucksEnv(true);
 }
 
 describe("nunjucks rendering", () => {

js/src/template/nunjucks-utils.ts

@@ -2,7 +2,7 @@ import * as nunjucks from "nunjucks";
 
 export function lintTemplate(template: string, context: any): void {
   const env = new nunjucks.Environment(null, {
-    autoescape: true,
+    autoescape: false,
     throwOnUndefined: true,
   });
   env.renderString(template, context);

js/src/template/renderer.test.ts

@@ -82,4 +82,74 @@ describe("renderTemplateContent", () => {
     });
     expect(result).toBe("Data: 42");
   });
+
+  test("renders objects as JSON strings in mustache (not [object Object])", () => {
+    const varsWithObject = {
+      user: { name: "Alice", age: 30 },
+      items: ["a", "b", "c"],
+    };
+    const result = renderTemplateContent(
+      "User: {{user}}, Items: {{items}}",
+      varsWithObject,
+      escape,
+      { templateFormat: "mustache" },
+    );
+    expect(result).toBe(
+      'User: {"name":"Alice","age":30}, Items: ["a","b","c"]',
+    );
+    expect(result).not.toContain("[object Object]");
+  });
+
+  test("renders objects as JSON strings in nunjucks (not [object Object])", () => {
+    const varsWithObject = {
+      user: { name: "Bob", age: 25 },
+      items: [1, 2, 3],
+    };
+    const result = renderTemplateContent(
+      "User: {{ user }}, Items: {{ items }}",
+      varsWithObject,
+      escape,
+      { templateFormat: "nunjucks" },
+    );
+    expect(result).toBe('User: {"name":"Bob","age":25}, Items: [1,2,3]');
+    expect(result).not.toContain("[object Object]");
+  });
+
+  test("renders nested objects as JSON strings in mustache", () => {
+    const varsWithNested = {
+      data: {
+        nested: {
+          value: 123,
+          items: ["x", "y"],
+        },
+      },
+    };
+    const result = renderTemplateContent(
+      "Data: {{data}}",
+      varsWithNested,
+      escape,
+      { templateFormat: "mustache" },
+    );
+    expect(result).toBe('Data: {"nested":{"value":123,"items":["x","y"]}}');
+    expect(result).not.toContain("[object Object]");
+  });
+
+  test("renders nested objects as JSON strings in nunjucks", () => {
+    const varsWithNested = {
+      config: {
+        settings: {
+          enabled: true,
+          count: 5,
+        },
+      },
+    };
+    const result = renderTemplateContent(
+      "Config: {{ config }}",
+      varsWithNested,
+      escape,
+      { templateFormat: "nunjucks" },
+    );
+    expect(result).toBe('Config: {"settings":{"enabled":true,"count":5}}');
+    expect(result).not.toContain("[object Object]");
+  });
 });