REPL doesn't work with nested proxies

[geeksilva97]

Version

23.10.0

Platform

Darwin LM-JNVH7RPW6J 23.6.0 Darwin Kernel Version 23.6.0: Thu Dec 19 20:47:53 PST 2024; root:xnu-10063.141.1.703.2~1/RELEASE_ARM64_T6030 arm64

Subsystem

repl

What steps will reproduce the bug?

1. Open the repl ( type node)
2. Paste the following code

  const handler = {
    get(target, prop, receiver) {
      console.log(`Accessed prop: ${String(prop)}`);

      return new Proxy(function () {}, {
        apply: function (_target, _thisArg, args) {
          console.log(`Called function: ${String(prop)} with args:`, args);
          return `Result of calling ${prop}`;
        },
        get: function (_target, subProp) {
          console.log(`Accessed nested prop: ${String(subProp)} on ${String(prop)}`);
          return `Nested value of ${subProp}`;
        }
      });
    }
  };

  const obj = new Proxy({}, handler);

3. Try to access a nested prop like obj.hello.world.

How often does it reproduce? Is there a required condition?

Always

What is the expected behavior? Why is that the expected behavior?

It should allow me to type something like obj.hello.world.

What do you see instead?

I can type obj.hello but once I type the other dot, it already triggers the proxy. See the video:

node-repl-proxy-issue.mov

Additional information

No response

[BridgeAR]

I guess it is related to the input preview triggering util.inspect on it.

[dario-piotrowicz]

I'm pretty sure this is caused by the REPL completer 🤔

Example

The following code reproduces the issue:

const repl = require('node:repl');

const r = repl.start();

r.write(`
  const handler = {
    get(target, prop, receiver) {
      console.log(\`Accessed prop: \${String(prop)}\`);

      return new Proxy(function () {}, {
        apply: function (_target, _thisArg, args) {
          console.log(\`Called function: \${String(prop)} with args:\`, args);
          return \`Result of calling \${prop}\`;
        },
        get: function (_target, subProp) {
          console.log(\`Accessed nested prop: \${String(subProp)} on \${String(prop)}\`);
          return \`Nested value of \${subProp}\`;
        }
      });
    }
  };

  const obj = new Proxy({}, handler);
`);

(+ typing obj.hello.world of course)

But the following, where the completer if overridden by a noop function does not:

const repl = require('node:repl');

const r = repl.start({
    completer: () => {
        return [[], ''];
    },
});

r.write(`
  const handler = {
    get(target, prop, receiver) {
      console.log(\`Accessed prop: \${String(prop)}\`);

      return new Proxy(function () {}, {
        apply: function (_target, _thisArg, args) {
          console.log(\`Called function: \${String(prop)} with args:\`, args);
          return \`Result of calling \${prop}\`;
        },
        get: function (_target, subProp) {
          console.log(\`Accessed nested prop: \${String(subProp)} on \${String(prop)}\`);
          return \`Nested value of \${subProp}\`;
        }
      });
    }
  };

  const obj = new Proxy({}, handler);
`);

(+ typing obj.hello.world of course)

Actually based on the following code comment I think that this is a known limitation/issue

node/lib/repl.js

Lines 1314 to 1315 in 09ecd2e

	// Warning: This eval's code like "foo.bar.baz", so it will run property
	// getter code.

[dario-piotrowicz]

Yeah here it is:

node/lib/repl.js

Line 1519 in 09ecd2e

this.eval(evalExpr, this.context, getREPLResourceName(), (e, obj) => {

this is the eval triggering the getter...

mh... I can't imagine how this could be fixed... besides maybe disabling the completer on nested object fields

would that be a valid tradeoff? maybe it could be done behind a flag? 🤔