bun.sh/test/js/node/util/node-inspect-tests/parallel/util-inspect-proxy.test.js

import assert from "assert";
import util from "util";
const opts = { showProxy: true };

test("no assertion failures", () => {
  let proxyObj;
  let called = false;
  const target = {
    [util.inspect.custom](depth, { showProxy }) {
      if (showProxy === false) {
        called = true;
        if (proxyObj !== this) {
          throw new Error("Failed");
        }
      }
      return [1, 2, 3];
    },
  };
  const handler = {
    getPrototypeOf() {
      throw new Error("getPrototypeOf");
    },
    setPrototypeOf() {
      throw new Error("setPrototypeOf");
    },
    isExtensible() {
      throw new Error("isExtensible");
    },
    preventExtensions() {
      throw new Error("preventExtensions");
    },
    getOwnPropertyDescriptor() {
      throw new Error("getOwnPropertyDescriptor");
    },
    defineProperty() {
      throw new Error("defineProperty");
    },
    has() {
      throw new Error("has");
    },
    get(_, key) {
      throw new Error("get: " + String(key));
    },
    set() {
      throw new Error("set");
    },
    deleteProperty() {
      throw new Error("deleteProperty");
    },
    ownKeys() {
      throw new Error("ownKeys");
    },
    apply() {
      throw new Error("apply");
    },
    construct() {
      throw new Error("construct");
    },
  };
  proxyObj = new Proxy(target, handler);

  // Inspecting the proxy should not actually walk it's properties
  util.inspect(proxyObj, opts);

  // Make sure inspecting object does not trigger any proxy traps.
  util.format("%s", proxyObj);

  const r = Proxy.revocable({}, {});
  r.revoke();

  assert.strictEqual(util.inspect(r.proxy), "<Revoked Proxy>");
  assert.strictEqual(
    util.inspect(r, { showProxy: true }),
    "{ proxy: <Revoked Proxy>, revoke: [Function (anonymous)] }",
  );

  assert.strictEqual(util.format("%s", r.proxy), "<Revoked Proxy>");

  assert.strictEqual(
    util.inspect(proxyObj, opts),
    "Proxy [\n" +
      "  [ 1, 2, 3 ],\n" +
      "  {\n" +
      "    getPrototypeOf: [Function: getPrototypeOf],\n" +
      "    setPrototypeOf: [Function: setPrototypeOf],\n" +
      "    isExtensible: [Function: isExtensible],\n" +
      "    preventExtensions: [Function: preventExtensions],\n" +
      "    getOwnPropertyDescriptor: [Function: getOwnPropertyDescriptor],\n" +
      "    defineProperty: [Function: defineProperty],\n" +
      "    has: [Function: has],\n" +
      "    get: [Function: get],\n" +
      "    set: [Function: set],\n" +
      "    deleteProperty: [Function: deleteProperty],\n" +
      "    ownKeys: [Function: ownKeys],\n" +
      "    apply: [Function: apply],\n" +
      "    construct: [Function: construct]\n" +
      "  }\n" +
      "]",
  );

  // Inspecting a proxy without the showProxy option set to true should not
  // trigger any proxy handlers.
  assert.strictEqual(util.inspect(proxyObj), "[ 1, 2, 3 ]");
  assert(called);

  // Yo dawg, I heard you liked Proxy so I put a Proxy
  // inside your Proxy that proxies your Proxy's Proxy.
  const proxy1 = new Proxy({}, {});
  const proxy2 = new Proxy(proxy1, {});
  const proxy3 = new Proxy(proxy2, proxy1);
  const proxy4 = new Proxy(proxy1, proxy2);
  const proxy5 = new Proxy(proxy3, proxy4);
  const proxy6 = new Proxy(proxy5, proxy5);
  const expected0 = "{}";
  const expected1 = "Proxy [ {}, {} ]";
  const expected2 = "Proxy [ Proxy [ {}, {} ], {} ]";
  const expected3 = "Proxy [ Proxy [ Proxy [ {}, {} ], {} ], Proxy [ {}, {} ] ]";
  const expected4 = "Proxy [ Proxy [ {}, {} ], Proxy [ Proxy [ {}, {} ], {} ] ]";
  const expected5 =
    "Proxy [\n  " +
    "Proxy [ Proxy [ Proxy [Array], {} ], Proxy [ {}, {} ] ],\n" +
    "  Proxy [ Proxy [ {}, {} ], Proxy [ Proxy [Array], {} ] ]" +
    "\n]";
  const expected6 =
    "Proxy [\n" +
    "  Proxy [\n" +
    "    Proxy [ Proxy [Array], Proxy [Array] ],\n" +
    "    Proxy [ Proxy [Array], Proxy [Array] ]\n" +
    "  ],\n" +
    "  Proxy [\n" +
    "    Proxy [ Proxy [Array], Proxy [Array] ],\n" +
    "    Proxy [ Proxy [Array], Proxy [Array] ]\n" +
    "  ]\n" +
    "]";
  assert.strictEqual(util.inspect(proxy1, { showProxy: 1, depth: null }), expected1);
  assert.strictEqual(util.inspect(proxy2, opts), expected2);
  assert.strictEqual(util.inspect(proxy3, opts), expected3);
  assert.strictEqual(util.inspect(proxy4, opts), expected4);
  assert.strictEqual(util.inspect(proxy5, opts), expected5);
  assert.strictEqual(util.inspect(proxy6, opts), expected6);
  assert.strictEqual(util.inspect(proxy1), expected0);
  assert.strictEqual(util.inspect(proxy2), expected0);
  assert.strictEqual(util.inspect(proxy3), expected0);
  assert.strictEqual(util.inspect(proxy4), expected0);
  assert.strictEqual(util.inspect(proxy5), expected0);
  assert.strictEqual(util.inspect(proxy6), expected0);

  // Just for fun, let's create a Proxy using Arrays.
  const proxy7 = new Proxy([], []);
  const expected7 = "Proxy [ [], [] ]";
  assert.strictEqual(util.inspect(proxy7, opts), expected7);
  assert.strictEqual(util.inspect(proxy7), "[]");

  // Now we're just getting silly, right?
  const proxy8 = new Proxy(Date, []);
  const proxy9 = new Proxy(Date, String);
  const expected8 = "Proxy [ [Function: Date], [] ]";
  const expected9 = "Proxy [ [Function: Date], [Function: String] ]";
  assert.strictEqual(util.inspect(proxy8, opts), expected8);
  assert.strictEqual(util.inspect(proxy9, opts), expected9);
  assert.strictEqual(util.inspect(proxy8), "[Function: Date]");
  assert.strictEqual(util.inspect(proxy9), "[Function: Date]");

  const proxy10 = new Proxy(() => {}, {});
  const proxy11 = new Proxy(() => {}, {
    get() {
      return proxy11;
    },
    apply() {
      return proxy11;
    },
  });
  const expected10 = "[Function (anonymous)]";
  const expected11 = "[Function (anonymous)]";
  assert.strictEqual(util.inspect(proxy10), expected10);
  assert.strictEqual(util.inspect(proxy11), expected11);
});