[Feature]: lint in-memory files via the Node API (no disk write)

[jantimon]

What problem does this feature solve?

I run an LLM coding agent (Node/TS) that generates code and lints file changes before before storing them in the databse. The point is to catch the dumb render-breaking stuff inside the generation loop especially conditional hooks or const reassignment

Afaik today rslint only supports linting real files on disk

Current linters with in-memory:

• eslint: lintText(code, { filePath }), works
• biome: in-process Node API, lintContent(projectKey, content, { filePath }), works
• oxlint: disk only
• rslint: disk only

We are using Biome for this because it's the only fast linter with a real in-process Node API right now but I would rather be on rslint to not mix both stacks

What does the proposed API of configuration look like?

Maybe mirror Biome's shape somehow like this (or even better to support ts-go or other cross file lintings)

import { Rslint } from "@rslint/core";

const rslint = new Rslint();
const { projectKey } = rslint.openProject("/");
rslint.applyConfiguration(projectKey, config);

const { diagnostics } = rslint.lintContent(projectKey, source, {
  filePath: "virtual/Component.tsx", // virtual, never written to disk
});

here's my current Biome setup:

import { Biome, type Configuration } from "@biomejs/js-api/nodejs";

const biome = new Biome();
const { projectKey } = biome.openProject("/");
biome.applyConfiguration(projectKey, config);

const { diagnostics } = biome.lintContent(projectKey, content, { filePath });
// map diagnostics -> { path, line, column, rule, severity, message }

[chenjiahan]

I think it would be valuable for Rslint to provide a JS API similar to ESLint’s lintText @fansenze cc

[mvanhorn]

Opened #1136 implementing this: a lintText(code, options?) convenience function (plus a matching RSLintService.lintText method) that lints an in-memory source string under a virtual filePath via the existing fileContents VFS plumbing, no disk write. Mirrors ESLint's lintText. No Go/server changes.

[fansenze]

@jantimon Hi! @rslint/core@0.6.4 already supports in-memory linting through the Rslint Node API. You can refer to this documentation for usage details: https://rslint.rs/guide/js-api#fully-in-memory-linting.

[jantimon]

thank you so much - I will give it a try