Invalid reporting of `no-unused-expressions` for `_.{keys(mainnets).length}`

[PaulRBerg]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and discussions and couldn’t find anything (or linked relevant results below)

Affected package

eslint-plugin-mdx

Steps to reproduce

See the use of _.keys here:

---
id: chains
title: Supported Chains
sidebar_position: 7
---

import Link from "@docusaurus/Link";
import Chains from "@site/src/components/organisms/Chains";
import { Links } from "@site/src/constants";
import _ from "lodash";
import { mainnets, testnets } from "sablier";

Sablier Protocol is live on {_.keys(mainnets).length} mainnets and {_.keys(testnets).length} testnets, although not all of these chains are supported by the
[Sablier Interface](https://app.sablier.com/). If you're interested in having your chain listed in the Interface, fill out <Link href={Links.Forms.CALL}>this form</Link>.

Actual behavior

13:30  error  Expected an assignment or function call and instead saw an expression  no-unused-expressions

Expected behavior

There should be no error because that is perfectly legitimate MDX code. It compiles.

Runtime

No response

Package manager

bun

Operating system

macOS@15.5

Build and bundle tools

Docusaurus

[JounQin]

Similar to #444

Workaround: add a <> wrapper

[PaulRBerg]

If I add <> wrapper like this:

<{_.keys(mainnets).length}>

I am getting an error like this:

Preprocessing error: Unexpected character `{` (U+007B) before name, expected a character that can start a name, such as a letter, `$`, or `_`

---

Edit

Nevermind, I figured it out. You meant doing this:

<>{_.keys(mainnets).length}</>

[JounQin]

I mean the following actually:

<>

Sablier Protocol is live on {_.keys(mainnets).length} mainnets and {_.keys(testnets).length} testnets, although not all of these chains are supported by the
[Sablier Interface](https://app.sablier.com/). If you're interested in having your chain listed in the Interface, fill out <Link href={Links.Forms.CALL}>this form</Link>.

</>

[JounQin]

@PaulRBerg @ChristianMurphy

Do you think we should just disable no-unused-expressions rule for .mdx, I found there were no invalid use case for .mdx files?

[remcohaszing]

# Hello

export function whatever() {
  // This expression is unused
  1;
}

[JounQin]

Thanks @remcohaszing for pointing out! Then maybe we need to have our own mdx/no-unused-expressions now.

[PaulRBerg]

A custom mdx/no-unused-expressions sounds good